Working at 8 / 16 / 32 bits per channel…

S
Posted By
Smurfy
Mar 13, 2009
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3769
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82
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How many of you work at higher bits per channel than 8?

Will gradients be rendered more smoothly in those situations?

What do printers do with those files? Any problems?

When should one work at 16 or 32 bits per channel?

Thanks.
N
nomail
Mar 13, 2009
Adam wrote:

How many of you work at higher bits per channel than 8?

Nobody can tell you how many of us do that.

Will gradients be rendered more smoothly in those situations?

Perhaps they do, but as most screens do not support more than 8 bits, you won’t see it. Working in 16 bits matters for *editting* those gradients (and other things).

What do printers do with those files? Any problems?

Most printers do not use 16 bits, but sending a 16 bits file to a printer doesn’t cause any problems. The driver will change it to 8 bits.

When should one work at 16 or 32 bits per channel?

32 bits is for HDR (High Dynamic Range) photography only.


Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.com
JJ
John J
Mar 13, 2009
Johan W. Elzenga wrote:
32 bits is for HDR (High Dynamic Range) photography only.

Today I read a claim that editing in 16 or 32-bit reduced rounding errors, thus increasing quality. Rubbish?

And is this just snake-oil?
http://www.epson.com/cgi-bin/Store/jsp/ProImaging/EpsonInnov ations.do?invMoreInfo=EpsonInv16BitPrinterDrivers
G
gowanoh
Mar 13, 2009
This is an ancient, by digital standards, issue.
The answer is the same as the medieval question about how many angels can sit on the head of a pin.
Oils vs acrylics.
First of all many photographers would be surprised to learn that there is a good chance they are judging images on a 6 bit LCD panel, particularly if their computer is named after a fruit.
The widest photo printer gamuts are in the 8 bit realm, offset printing even less.
Raw images are most commonly captured in 12 bits, some now 14, truncated to 8 bits when opened, or if opened as 16 bit images most processes will be applied on bits that contain no information.
The idea that processing a 12 or 14 bit raw image in 16 bits is better than processing it at 8 bits is technically correct with regard to yielding more smoothly curved plots of the colors at the extremes of the gamut. Does this make any practical difference when the final image will be viewed via a medium that is incapable of accurately reproducing that color gamut anyway?
As I recall Epson used to be very upfront in their literature on the 8 vs 16 bit issue from the printer standpoint but I don’t know if they are officially still as truthy. They showed graphs and actual color mismatches generated by working in 16 bits.
Does it make sense to send a 16 bit file, most containing empty data, to a printer driver that will arbitrarily strip it down to 8 bits and think this will render a better image –if you pay Apple prices for "new" but already obsolete Intel hardware the answer is obviously yes, but to those who still have the capacity to reason the answer may not be yes.
If you think working in 8 bits, 16 bits, LAB color or whatever works for you then that is all that counts.
JJ
John J
Mar 14, 2009
pupick wrote:

First of all many photographers would be surprised to learn that there is a good chance they are judging images on a 6 bit LCD panel,

It would be fair to specify exactly what monitors are/were 6-bit – the Apple 20" was one, I think. But not all of them are.
MR
Mike Russell
Mar 14, 2009
On Fri, 13 Mar 2009 08:44:04 -0400, Adam wrote:

How many of you work at higher bits per channel than 8?

A significant number of people do

Will gradients be rendered more smoothly in those situations?

If you mean a gradient from a photograph, no. If you mean a computer generated gradient, yes, in some situations, particularly if you are speaking of a mathematical smoothness, and not a visual one.

What do printers do with those files? Any problems?

Usually no problems at all.

When should one work at 16 or 32 bits per channel?

8 vs 16 is a personal preference. Some people simply want the extra bits, periodm and feel that anything less is compromising quality. My main interest is in producing tools that they can use, rather than convincing them as to one workflow or another.

16 bits is also required to prevent artificial banding in unusually leggy color spaces, such as ProPhoto RGB and Wide Gamut RGB. 32 bits is useful for a number of applications, including, as Johan says, HDR images, and other high dynamic range images such as combined astronomical images. —
Mike Russell – http://www.curvemeister.com
JJ
John J
Mar 14, 2009
Mike Russell wrote:
On Fri, 13 Mar 2009 08:44:04 -0400, Adam wrote:

How many of you work at higher bits per channel than 8?

A significant number of people do

Will gradients be rendered more smoothly in those situations?

If you mean a gradient from a photograph, no. If you mean a computer generated gradient, yes, in some situations, particularly if you are speaking of a mathematical smoothness, and not a visual one.

Mike, am I correct that the reason a photograph’s graduated tone might not be as smooth is because it does not follow a regular transition?
N
nomail
Mar 15, 2009
John J wrote:

Johan W. Elzenga wrote:
32 bits is for HDR (High Dynamic Range) photography only.

Today I read a claim that editing in 16 or 32-bit reduced rounding errors, thus increasing quality. Rubbish?

No, and I never said it was. However, because there are no input devices (cameras, scanners) that have *more than* 16 bits/color depth, there is no reason to work in *more than* 16 bits for single images. Only HDR gives you the need for 32 bits. That’s what I said and I stand by it.

And is this just snake-oil?
http://www.epson.com/cgi-bin/Store/jsp/ProImaging/EpsonInnov ations.do?invM oreInfo=EpsonInv16BitPrinterDrivers

READ what I said, please. There are indeed *SOME* printers that can handle 16 bits files. But like I said, *MOST* printers cannot. The question was: does it create problems? My answer was, no it does not. I stand by that too.


Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.com
JJ
John J
Mar 16, 2009
Johan W. Elzenga wrote:
John J wrote:

Johan W. Elzenga wrote:
32 bits is for HDR (High Dynamic Range) photography only.
Today I read a claim that editing in 16 or 32-bit reduced rounding errors, thus increasing quality. Rubbish?

No, and I never said it was. However, because there are no input devices (cameras, scanners) that have *more than* 16 bits/color depth, there is no reason to work in *more than* 16 bits for single images. Only HDR gives you the need for 32 bits. That’s what I said and I stand by it.

I did not suggest that you mentioned rounding errors, nor did I disagree with comments about HDR.

I simply asked whether rounding errors are a significant problem. I think they are not.
MR
Mike Russell
Mar 16, 2009
On Sat, 14 Mar 2009 09:38:08 -0500, John J wrote:

Mike, am I correct that the reason a photograph’s graduated tone might not be as smooth is because it does not follow a regular transition?

Yes. This is a good description of what causes banding – an irregular transition in one or more color channels that creates a visible edge or ripple, aka "band" in an otherwise smooth gradient. When this happens, the photographer has lost tonal control of the image.

Mike Russell – http://www.curvemeister.com
N
nomail
Mar 16, 2009
John J wrote:

Johan W. Elzenga wrote:
John J wrote:

Johan W. Elzenga wrote:
32 bits is for HDR (High Dynamic Range) photography only.
Today I read a claim that editing in 16 or 32-bit reduced rounding errors, thus increasing quality. Rubbish?

No, and I never said it was. However, because there are no input devices (cameras, scanners) that have *more than* 16 bits/color depth, there is no reason to work in *more than* 16 bits for single images. Only HDR gives you the need for 32 bits. That’s what I said and I stand by it.

I did not suggest that you mentioned rounding errors, nor did I disagree with comments about HDR.

I simply asked whether rounding errors are a significant problem. I think they are not.

Editting in 16 bits does give an advantage over editting in 8 bits, even though you often do not see it clearly on your monitor. It depends on the kind of images.


Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.com
R
Roberto
Apr 7, 2009
Actually John rounding errors are a much bigger problem than you think. In fact it can be used to interesting effect. Back in the days of CS2 Russell Brown of Adobe created a free script for Photoshop called shake, rattle and roll. This script made use of the rounding errors in Photoshop to create some very interesting effects. While the script unfortunately has never been updated for CS3 or CS4 you can still do it manually.

If you would like to see just how bad and how quickly rounding errors can affect your images load a low resolution image (high resolution will work but will take longer) and then rotate the image by 8 degrees using the transform tool. Now repeat this over and over again. Do it 20 or 30 times and you will see that the image is slowly destroyed, this is because of rounding errors in Photoshop. The script I mentioned did other things for example it would rotate back and forth, spin it around and things like this to give some very interesting effects. If you would like to get an idea of the effect keep rotating the image the more you do it the more dramatic the effect.

I have tried to get Russell to update the script but he says he doesn’t have the time.

The moral of this is don’t transform any more than you have to. Each time you do you damage the image. It may take some doing to notice it, but the damage is happening from transformation one. This is also just one area of Photoshop that has rounding errors. Now does this mean that in 16-bit or 32-bit that you have less rounding errors or get less damge I don’t know, I don’t care. I never transform an image enough to really worry about it. And, since just about any output is 8-bit it just isn’t worth the trouble in my opinion. If others thing it is awesome, have fun.

Robert
E
erpy
Apr 7, 2009
John J:
Johan W. Elzenga wrote:
32 bits is for HDR (High Dynamic Range) photography only.

Today I read a claim that editing in 16 or 32-bit reduced rounding errors, thus increasing quality. Rubbish?

And is this just snake-oil?
http://www.epson.com/cgi-bin/Store/jsp/ProImaging/EpsonInnov ations.do?invMoreInfo=EpsonInv16BitPrinterDrivers

That’s correct.
16bit and 32bit floating point linear editing yields much more precision when using many layers with different effects/adjustments. When using only a few layers it might not be that noticeable… otherwise it makes much more difference.

As for 32bit editing in Photoshop, it depends whether Adobe is dedicating part of the precision to HDR data or not.
Anyway, 32bit floating point editing is much more precise than 16bit (which is integer anyway).

See: http://en.wikipedia.org/wiki/Floating_point
MR
Mike Russell
Apr 7, 2009
On Tue, 07 Apr 2009 20:58:57 +0200, erpy wrote:

As for 32bit editing in Photoshop, it depends whether Adobe is dedicating part of the precision to HDR data or not.
Anyway, 32bit floating point editing is much more precise than 16bit (which is integer anyway).

Any examples where any of this matters? Didn’t think so.


Mike Russell – http://www.curvemeister.com
M
mike
Apr 7, 2009
In article <49db74a3$0$95539$
says…
Actually John rounding errors are a much bigger problem than you think. In fact it can be used to interesting effect. Back in the days of CS2 Russell Brown of Adobe created a free script for Photoshop called shake, rattle and roll. This script made use of the rounding errors in Photoshop to create some very interesting effects. While the script unfortunately has never been updated for CS3 or CS4 you can still do it manually.

If you would like to see just how bad and how quickly rounding errors can affect your images load a low resolution image (high resolution will work but will take longer) and then rotate the image by 8 degrees using the transform tool. Now repeat this over and over again. Do it 20 or 30 times and you will see that the image is slowly destroyed, this is because of rounding errors in Photoshop. The script I mentioned did other things for example it would rotate back and forth, spin it around and things like this to give some very interesting effects. If you would like to get an idea of the effect keep rotating the image the more you do it the more dramatic the effect.
I think this has very little to do with the bit-depth of the image and almost everything to do with the resolution of the image. For example, create a small 8-bit per channel image (100×100 pixels square is fine) and draw a vertical black single pixel width line down the centre of the white background. Now apply an arbitrary rotation like 4.56 degrees (don’t choose an angle that is a factor of 360) and apply iy just once. Now repeat by rotating in the opposite direction by the same angle.If you zoom into the image far enough to see the individual pixels as monotone squares you will note that the line is now a fuzzy shape approximately 2 pixels wide (with outliers up to 3-4 pixels wide) in shades of grey. This is not due to any lack of bit depth as the result is almost identical if you repeat the task with a 16-bit image. Rather it is due to the fact that, when rotated, the pixels of the line don’t map exactly onto individual new pixels so their colour value is ‘smeared’ across 4 or more neighbouring pixels. So it is a resolution issue. If you repeat the experiment with a 10 pixel wide line in a 1000×1000 image, you can see that at the same scale of magnificatiobn there is less apparent damage to the line.

Mike
JJ
John J
Apr 8, 2009
In article <49db74a3$0$95539$
says…
Actually John rounding errors are a much bigger problem than you think. In fact it can be used to interesting effect. Back in the days of CS2 Russell Brown of Adobe created a free script for Photoshop called shake, rattle and roll. This script made use of the rounding errors in Photoshop to create some very interesting effects. While the script unfortunately has never been updated for CS3 or CS4 you can still do it manually.

If you would like to see just how bad and how quickly rounding errors can affect your images load a low resolution image (high resolution will work but will take longer) and then rotate the image by 8 degrees using the transform tool. Now repeat this over and over again. Do it 20 or 30 times and you will see that the image is slowly destroyed,

I use photoshop for photographs. I don’t ever need to manipulate the image in such bizarre ways.
R
Roberto
Apr 8, 2009
Mike we are talking about round errors and if they can have a visible effect on the image. If you try my suggestion you will see that the round errors can really have an impact and pretty quickly, surprisingly quickly. I made and make no statement on wheater 8-bit, 16-bit or 32-bit mode will increase or reduce rounding errors. I don’t know and I really don’t care. What I was trying to show is that round errors are there and they have affect your images and the rounding errors are quite easy to encounter.

Robert
R
Roberto
Apr 8, 2009
No per my example no. But, it does show that if you have to do more than one or two transformations (rotations to straighten a horrizon), resize up or down, correct for keystoning and the like you are definately damaging your images as you are then encountering rounding errors. All of the tranformation tools introduce data damage to your image (except for flip horzontal and flip verticle. All of the others damage. So if you use any of the tools (and who knows what other tools) you are damaging your images. As a photographer myself you can avoid having to use these tools at some point, it is best to keep their use to a minimum and not to keep applying them over and over to correct a single issue. Straigtening the horizon with a single application or rotate is fine, having to apply it several times to do it isn’t. Though honest using the ruler with the rotate command I see no reason why you would have to apply rotate more than once.

I am sure that many of the filters have rounding errors as well.

My point for my post was that rounding errors are real, they do damage your images and if you want to see them do it I provided a way to see it. Proof that they are real in other words. For most they won’t be a problem, but one needs to keep them in mind.

Robert
MR
Mike Russell
Apr 8, 2009
On Wed, 8 Apr 2009 09:22:12 +1200, mike wrote:

I think this has very little to do with the bit-depth of the image and almost everything to do with the resolution of the image.

Good point. I did the experiment. Applying repeated rotations to an 8 bit image, versus a 16 bit image, results in nearly the same result. Doubling the resolution preserves image detail much better, will both 8 bit and 16 bit producing nearly identical results.

http://www.curvemeister.com/forum/index.php?topic=2569

Mike Russell – http://www.curvemeister.com
HD
Henk de Jong
Apr 8, 2009
How many of you work at higher bits per channel than 8?
Will gradients be rendered more smoothly in those situations? What do printers do with those files? Any problems?
When should one work at 16 or 32 bits per channel?
Thanks.

This question has been asked many times. Part of it is answered in this article:
http://www.creativepro.com/article/out-of-gamut-the-high-bit -advantage

With kind regards,
Henk de Jong

http://www.hsdejong.nl
Nepal and Myanmar (Burma) – Photo Galleries
MR
Mike Russell
Apr 8, 2009
On Wed, 8 Apr 2009 09:21:42 +0200, Henk de Jong wrote:

This question has been asked many times. Part of it is answered in this article:
http://www.creativepro.com/article/out-of-gamut-the-high-bit -advantage

With kind regards,
Henk de Jong

Have you tried to duplicate what the article describes? I have. —
Mike Russell – http://www.curvemeister.com
J
Joel
Apr 8, 2009
Mike Russell wrote:

On Wed, 8 Apr 2009 09:22:12 +1200, mike wrote:

I think this has very little to do with the bit-depth of the image and almost everything to do with the resolution of the image.

Good point. I did the experiment. Applying repeated rotations to an 8 bit image, versus a 16 bit image, results in nearly the same result. Doubling the resolution preserves image detail much better, will both 8 bit and 16 bit producing nearly identical results.

In general it pretty much depends on the codition of the photo, or how much detail and large you want to print. Example

– If you have to work on some detail of a small photo (like 200-400K) then you may want to switch to 16-bit mode.

– If you want to work on detail of a photo taken by average P&S, then you may want to give 16-bit a try.

– If you work on a photo taken by high-end DSLR camera with good lens, and you just want to print 8×10 or little larger then 8-bit should be fine. If have to work on the EDGE and need to print to something like 20×30 or larger then you may want to try 16-bit with the combination of Photoshop’s Enlarger feature.

– If you work on a photo taken by high-end camera but with poor lens or some damaged channel etc. then you may need to give 16-bit mode a try.

There is a HUGE difference between 8-bit and 16-bit, and depend on the photo or condition you may have to zoom in 200-300% or so to learn the difference. With the lousy photo you should be able to see without zooming.
JJ
John J
Apr 8, 2009
Robert Barnett wrote:

My point for my post was that rounding errors are real, they do damage your images and if you want to see them do it I provided a way to see it.

He who needs to do excessive iterative rotations for a photograph, or has to make so very many non-adjustment layer manipulations to a photograph can live with the degradation alleged to occur through rounding errors.

Only someone with more monitor time than lifetime can care about such unrealistic bench-racing metrics that require a damned spreadsheet to ‘see’ and still have nothing to do with real-world outcomes as it regards photography.
J
jaSPAMc
Apr 8, 2009
John J found these unused words:

Robert Barnett wrote:

My point for my post was that rounding errors are real, they do damage your images and if you want to see them do it I provided a way to see it.

He who needs to do excessive iterative rotations for a photograph, or has to make so very many non-adjustment layer manipulations to a photograph can live with the degradation alleged to occur through rounding errors.

Only someone with more monitor time than lifetime can care about such unrealistic bench-racing metrics that require a damned spreadsheet to ‘see’ and still have nothing to do with real-world outcomes as it regards photography.

Another "Close is good enough"?
E
erpy
Apr 8, 2009
Mike Russell:
On Tue, 07 Apr 2009 20:58:57 +0200, erpy wrote:

As for 32bit editing in Photoshop, it depends whether Adobe is dedicating part of the precision to HDR data or not.
Anyway, 32bit floating point editing is much more precise than 16bit (which is integer anyway).

Any examples where any of this matters? Didn’t think so.

Whenever you need a smooth result with many layers using different blending modes.
You can do this easy test… sometimes you see this banding artifact on TV adverts too…

– make a new 24bit image, let’s say HD 1080 resolution, pick two close colors, say RGB(0,100,100) and RGB(0,150,150)
– make a radial gradient from the center to one corner of the picture. – Duplicate twice the layer and set the duplicates to Multiply. Duplicate twice again and set these other duplicates to Overlay. – Notice the banding.(100% zoom)
– Convert the image to 16 bit/component…
– The banding is gone.

M
mike
Apr 8, 2009
In article ,
says…
On Wed, 8 Apr 2009 09:22:12 +1200, mike wrote:

I think this has very little to do with the bit-depth of the image and almost everything to do with the resolution of the image.

Good point. I did the experiment. Applying repeated rotations to an 8 bit image, versus a 16 bit image, results in nearly the same result. Doubling the resolution preserves image detail much better, will both 8 bit and 16 bit producing nearly identical results.
This leads to an interesting possibility that I had not thought of before.

It is considered good practice by some to ‘upscale’ an 8 bit image to 16 bits before applying a whole bunch of colour corrections. If the image is then set back to 8 bits there are less rounding errors in the final image than if the whole process is carried out at 8 bits (and yes, I know there is debate as to whether it actually makes much difference for many images).

But what does appear a valid arguement to me is to up-scale the resolution of an image as much as possible before applying distortions (rotations, skew, scale, pinch, spherise, liquidise etc) then down-scale to the previous resolution. I tried a simple test where I drew a few 1 pixel wide lines and boxes of various colours on a 100×100 image. Then created a copy at 1000×1000 resolution. Applied identical rotation, pinch, and skew to both images then resized the larger image back to 100×100. The first image showed significant ‘smearing’ of line-shape and colours bled into neighbouring regions – the upscaled and then downscaled image showed much less of this (in fact most of the ‘damage’ to the second image was due to the downscaling process itself).

In a photographic image at 2-3000 pixel resolution this may not make much difference unless you went wild with the distortion process – but if you wanted to minimise ‘damage’ to fine details it might be worth while in some cases.

Mike
J
Joel
Apr 9, 2009
mike wrote:

In article ,
says…
On Wed, 8 Apr 2009 09:22:12 +1200, mike wrote:

I think this has very little to do with the bit-depth of the image and almost everything to do with the resolution of the image.

Good point. I did the experiment. Applying repeated rotations to an 8 bit image, versus a 16 bit image, results in nearly the same result. Doubling the resolution preserves image detail much better, will both 8 bit and 16 bit producing nearly identical results.
This leads to an interesting possibility that I had not thought of before.

It is considered good practice by some to ‘upscale’ an 8 bit image to 16 bits before applying a whole bunch of colour corrections. If the image is then set back to 8 bits there are less rounding errors in the final image than if the whole process is carried out at 8 bits (and yes, I know there is debate as to whether it actually makes much difference for many images).

But what does appear a valid arguement to me is to up-scale the resolution of an image as much as possible before applying distortions (rotations, skew, scale, pinch, spherise, liquidise etc) then down-scale to the previous resolution. I tried a simple test where I drew a few 1 pixel wide lines and boxes of various colours on a 100×100 image. Then created a copy at 1000×1000 resolution. Applied identical rotation, pinch, and skew to both images then resized the larger image back to 100×100. The first image showed significant ‘smearing’ of line-shape and colours bled into neighbouring regions – the upscaled and then downscaled image showed much less of this (in fact most of the ‘damage’ to the second image was due to the downscaling process itself).
In a photographic image at 2-3000 pixel resolution this may not make much difference unless you went wild with the distortion process – but if you wanted to minimise ‘damage’ to fine details it might be worth while in some cases.

Mike

As I have mentioned in other message that in general it won’t make much difference to a good hi-rez image. BUT some *original* good hi-rez image in the wrong hand of some RAW experted (the ones with wrong impression of RAW converter) can damage some color channel, then you may need 16-bit or 32-bit to get around the damage.

Years ago, I used to hand around Dpewview.com retouch forum to help other members, and I have seen many good images being destroyed by owners.
JJ
John J
Apr 9, 2009
Sir F. A. Rien wrote:
John J found these unused words:

Robert Barnett wrote:

My point for my post was that rounding errors are real, they do damage your images and if you want to see them do it I provided a way to see it.
He who needs to do excessive iterative rotations for a photograph, or has to make so very many non-adjustment layer manipulations to a photograph can live with the degradation alleged to occur through rounding errors.

Only someone with more monitor time than lifetime can care about such unrealistic bench-racing metrics that require a damned spreadsheet to ‘see’ and still have nothing to do with real-world outcomes as it regards photography.

Another "Close is good enough"?

If one cannot find a difference in these strange abstracted deviations from ‘the the thng itself’ (a photographic image) then the result is FAPP, nill, just usenet typing and meaningless. Let the bit-twi8ddler have their way; it has nothing to do with compelling imagery.
MR
Mike Russell
Apr 9, 2009
On Wed, 08 Apr 2009 06:34:11 -0500, Joel wrote:

There is a HUGE difference between 8-bit and 16-bit, and depend on the photo or condition you may have to zoom in 200-300% or so to learn the difference.

I’d like to see an image that demonstrates this.

Mike Russell – http://www.curvemeister.com
MR
Mike Russell
Apr 9, 2009
On Wed, 08 Apr 2009 20:57:07 +0200, erpy wrote:

Mike Russell:
On Tue, 07 Apr 2009 20:58:57 +0200, erpy wrote:

As for 32bit editing in Photoshop, it depends whether Adobe is dedicating part of the precision to HDR data or not.
Anyway, 32bit floating point editing is much more precise than 16bit (which is integer anyway).

Any examples where any of this matters? Didn’t think so.

Whenever you need a smooth result with many layers using different blending modes.
You can do this easy test… sometimes you see this banding artifact on TV adverts too…

– make a new 24bit image, let’s say HD 1080 resolution, pick two close colors, say RGB(0,100,100) and RGB(0,150,150)
– make a radial gradient from the center to one corner of the picture. – Duplicate twice the layer and set the duplicates to Multiply. Duplicate twice again and set these other duplicates to Overlay. – Notice the banding.(100% zoom)
– Convert the image to 16 bit/component…
– The banding is gone.

Gradient doesn’t count – gotta be a photograph for me to count it as an example.

Mike Russell – http://www.curvemeister.com
JP
John Passaneau
Apr 9, 2009
Another "Close is good enough"?

It is if your producing photographs. Maybe not if your producing pixels.

John Passaneau
J
jaSPAMc
Apr 9, 2009
John J found these unused words:

Sir F. A. Rien wrote:
John J found these unused words:

Robert Barnett wrote:

My point for my post was that rounding errors are real, they do damage your images and if you want to see them do it I provided a way to see it.
He who needs to do excessive iterative rotations for a photograph, or has to make so very many non-adjustment layer manipulations to a photograph can live with the degradation alleged to occur through rounding errors.

Only someone with more monitor time than lifetime can care about such unrealistic bench-racing metrics that require a damned spreadsheet to ‘see’ and still have nothing to do with real-world outcomes as it regards photography.

Another "Close is good enough"?

If one cannot find a difference in these strange abstracted deviations from ‘the the thng itself’ (a photographic image) then the result is FAPP, nill, just usenet typing and meaningless. Let the bit-twi8ddler have their way; it has nothing to do with compelling imagery.

Aw gee, you meant the ‘artistic critics’ judging my photos’ ‘technical merit’ have been wrong? It’s really the image that counts?
MR
Mike Russell
Apr 9, 2009
On Thu, 09 Apr 2009 09:26:36 -0700, Sir F. A. Rien wrote:

John J found these unused words:

Sir F. A. Rien wrote:
John J found these unused words:

Robert Barnett wrote:

My point for my post was that rounding errors are real, they do damage your images and if you want to see them do it I provided a way to see it.
He who needs to do excessive iterative rotations for a photograph, or has to make so very many non-adjustment layer manipulations to a photograph can live with the degradation alleged to occur through rounding errors.

Only someone with more monitor time than lifetime can care about such unrealistic bench-racing metrics that require a damned spreadsheet to ‘see’ and still have nothing to do with real-world outcomes as it regards photography.

Another "Close is good enough"?

If one cannot find a difference in these strange abstracted deviations from ‘the the thng itself’ (a photographic image) then the result is FAPP, nill, just usenet typing and meaningless. Let the bit-twi8ddler have their way; it has nothing to do with compelling imagery.

Aw gee, you meant the ‘artistic critics’ judging my photos’ ‘technical merit’ have been wrong? It’s really the image that counts?

They may have been wrong, or they may have been right. The only way to know would be to see some of your pix.

I am biased in favor of people who bring real names, as well as real photographs, to the table. The others, I agree with Robert, are just so much blather.

Mike Russell – http://www.curvemeister.com
E
erpy
Apr 9, 2009
Mike Russell ha scritto:
On Wed, 08 Apr 2009 20:57:07 +0200, erpy wrote:

Mike Russell:

On Tue, 07 Apr 2009 20:58:57 +0200, erpy wrote:

As for 32bit editing in Photoshop, it depends whether Adobe is dedicating part of the precision to HDR data or not.
Anyway, 32bit floating point editing is much more precise than 16bit (which is integer anyway).
Any examples where any of this matters? Didn’t think so.
Whenever you need a smooth result with many layers using different blending modes.
You can do this easy test… sometimes you see this banding artifact on TV adverts too…

– make a new 24bit image, let’s say HD 1080 resolution, pick two close colors, say RGB(0,100,100) and RGB(0,150,150)
– make a radial gradient from the center to one corner of the picture. – Duplicate twice the layer and set the duplicates to Multiply. Duplicate twice again and set these other duplicates to Overlay. – Notice the banding.(100% zoom)
– Convert the image to 16 bit/component…
– The banding is gone.

Gradient doesn’t count – gotta be a photograph for me to count it as an example.

Oh, well… someone please ban gradients from Photoshop because "they don’t count"… :))) Very scientific, or even logical, argument…. and a good laugh, thank you! :))

I thought the argument was about the "16 bits difference" per-se… not "for photographs". And I was actually right.
If you read the OP, he asks in fact:

"Will gradients be rendered more smoothly in those situations?"

the answer is: "Yes"

"When should one work at 16 or 32 bits per channel?"

the answer is: "Whenever you use many blending layers" … and even more so in conjuction with high resolutions.

E
erpy
Apr 9, 2009
Mike Russell ha scritto:
On Wed, 08 Apr 2009 20:57:07 +0200, erpy wrote:

Mike Russell:

On Tue, 07 Apr 2009 20:58:57 +0200, erpy wrote:

As for 32bit editing in Photoshop, it depends whether Adobe is dedicating part of the precision to HDR data or not.
Anyway, 32bit floating point editing is much more precise than 16bit (which is integer anyway).
Any examples where any of this matters? Didn’t think so.
Whenever you need a smooth result with many layers using different blending modes.
You can do this easy test… sometimes you see this banding artifact on TV adverts too…

– make a new 24bit image, let’s say HD 1080 resolution, pick two close colors, say RGB(0,100,100) and RGB(0,150,150)
– make a radial gradient from the center to one corner of the picture. – Duplicate twice the layer and set the duplicates to Multiply. Duplicate twice again and set these other duplicates to Overlay. – Notice the banding.(100% zoom)
– Convert the image to 16 bit/component…
– The banding is gone.

Gradient doesn’t count – gotta be a photograph for me to count it as an example.

Oh, and BTW, the digital photography argument would be too painful for users like you to take on.
That’s because it would show you both why you don’t notice much difference between an 8bit and a 16bit photo and at the same time how you’re being ripped off for good even with the most expensive camera on the whole market. (well, *maybe* excluding top-of-the-line Hasselblads)

MR
Mike Russell
Apr 9, 2009
On Fri, 10 Apr 2009 00:57:50 +0200, erpy wrote:

Oh, and BTW, the digital photography argument would be too painful for users like you to take on.
That’s because it would show you both why you don’t notice much difference between an 8bit and a 16bit photo and at the same time how you’re being ripped off for good even with the most expensive camera on the whole market. (well, *maybe* excluding top-of-the-line Hasselblads)

I think you, and to be fair many others, are making the simplest of tautologies: "more bits is more better". Your discussion of an 8 bit gradient versus a 16 bit gradient can be equally well applied to a 16 bit gradient versus a 32 bit gradient, 32 bit and 64 bit, and so on. As Buzz Lightyear says, "to infinity, and beyond!".

At some point, I’m sure you will agree, the number of bits becomes "lost in the noise".For a photograph, the bedrock of whether this reasoning is valid or not should be in the form of an image that shows the effect. For a computer generated gradient, there is no noise, and therefore the tautology holds in Buzz Lightyear.

My challenge, which still stands, is to present a photographic image, in a normal color space such as sRGB or Adobe RGB, that edits better in 8 bit than 16 bit. Do you have one, or not? That’s all, very simple.

Here are some examples of quality variation that we can agree is real:

1) variation of image quality with jpeg quality – easily demonstrated, and not a source of discussion.
2) variation of image quality in the face of repeated transforms as a function of bit depth, and of image resolution. I presented an example illustrating this earlier in this thread.
3) variation of image quality for indexed versus 24 bit RGB images. Again, an example of this is easily provided.
4) variation of image quality with ISO setting.
5) variation of image quality with aperture setting.
6) variation of image quality with image stabilization.
7) the difference in image quality between a high quality jpeg and an uncompressed TIFF or raw image.

Each of the above are easily demonstrated using *photographic images*. But ah, according to you (and to be fair, others), variation of image quality versus bit depth is blazingly obvious. But, unlike the above seven examples, it is not so obvious that you can point to an example photograph, just a computer generated gradient which d nothing to do with nothing.


Mike Russell – http://www.curvemeister.com
JJ
John J
Apr 10, 2009
Mike Russell wrote:
[…]
They may have been wrong, or they may have been right. The only way to know would be to see some of your pix.

I am biased in favor of people who bring real names, as well as real photographs, to the table. The others, I agree with Robert, are just so much blather.

Mike, what would you like? URLs to digital representations of pictures?
MR
Mike Russell
Apr 10, 2009
On Thu, 09 Apr 2009 19:29:37 -0500, John J wrote:

Mike, what would you like? URLs to digital representations of pictures?

Sounds fine.

BTW, just to fill in a little bit, Rien and I have had this discussion before. His name is a play on the words "ca ne fait rien" meaning, "that doesn’t matter at all". He is tickled, a little, when people recognize the pun.

Mike Russell – http://www.curvemeister.com
J
Joel
Apr 10, 2009
Mike Russell wrote:

<snip>
At some point, I’m sure you will agree, the number of bits becomes "lost in the noise".For a photograph, the bedrock of whether this reasoning is valid or not should be in the form of an image that shows the effect. For a computer generated gradient, there is no noise, and therefore the tautology holds in Buzz Lightyear.

Talking about rockbed then why not using ROCK as an example. Now

– Throwing (100) 100×100" rocks on the ground

– Then also (10,000) 1×1" rocks on the ground

And which one looks smoother (flatter, more evenly)?

That’s pretty much same with 8-bit and 16-bit, or you will get more pixel from 16-bit then 8-bits, and if you spread them around then the more pixel the smoother.
MR
Mike Russell
Apr 10, 2009
On Thu, 09 Apr 2009 20:07:19 -0500, Joel wrote:

That’s pretty much same with 8-bit and 16-bit, or you will get more pixel from 16-bit then 8-bits, and if you spread them around then the more pixel the smoother.

You’ve got it backwards. If you keep the file size the same, an 8 bit image will store exactly twice the number of pixels as a 16 bit image.

IOW, if you are going to double the size of the file, it’s better to have twice as many 8 bit pixels, as it is to have the same number of 16 bit per channel pixels.

Mike Russell – http://www.curvemeister.com
J
Joel
Apr 10, 2009
Mike Russell wrote:

On Thu, 09 Apr 2009 20:07:19 -0500, Joel wrote:

That’s pretty much same with 8-bit and 16-bit, or you will get more pixel from 16-bit then 8-bits, and if you spread them around then the more pixel the smoother.

You’ve got it backwards. If you keep the file size the same, an 8 bit image will store exactly twice the number of pixels as a 16 bit image.
IOW, if you are going to double the size of the file, it’s better to have twice as many 8 bit pixels, as it is to have the same number of 16 bit per channel pixels.

May be I have everything in backwards, and that’s why I sometime switch to 16-mode to work on low-rez image. And I only use low-rez for DVD label.
MR
Mike Russell
Apr 10, 2009
On Thu, 09 Apr 2009 22:38:57 -0500, Joel wrote:

May be I have everything in backwards, and that’s why I sometime switch to 16-mode to work on low-rez image. And I only use low-rez for DVD label.

You may find that you like the results better – sharper lines, etc – if you change the ppi in Image Size, and work on a higher resolution image. When you’re done, resample back down to the original size using Bi-cubic Sharpen.

Mike Russell – http://www.curvemeister.com
JJ
John J
Apr 10, 2009
Joel wrote:
Mike Russell wrote:

<snip>
At some point, I’m sure you will agree, the number of bits becomes "lost in the noise".For a photograph, the bedrock of whether this reasoning is valid or not should be in the form of an image that shows the effect. For a computer generated gradient, there is no noise, and therefore the tautology holds in Buzz Lightyear.

Talking about rockbed then why not using ROCK as an example. Now
– Throwing (100) 100×100" rocks on the ground

– Then also (10,000) 1×1" rocks on the ground

And which one looks smoother (flatter, more evenly)?

That’s pretty much same with 8-bit and 16-bit, or you will get more pixel from 16-bit then 8-bits, and if you spread them around then the more pixel the smoother.

However, you view the image on a low-bit monitor (coarse sieve) and print to a low-bit printer.
J
jaSPAMc
Apr 10, 2009
Mike Russell found these unused words:

On Thu, 09 Apr 2009 09:26:36 -0700, Sir F. A. Rien wrote:
John J found these unused words:

Sir F. A. Rien wrote:
John J found these unused words:

Robert Barnett wrote:

My point for my post was that rounding errors are real, they do damage your images and if you want to see them do it I provided a way to see it.
He who needs to do excessive iterative rotations for a photograph, or has to make so very many non-adjustment layer manipulations to a photograph can live with the degradation alleged to occur through rounding errors.

Only someone with more monitor time than lifetime can care about such unrealistic bench-racing metrics that require a damned spreadsheet to ‘see’ and still have nothing to do with real-world outcomes as it regards photography.

Another "Close is good enough"?

If one cannot find a difference in these strange abstracted deviations from ‘the the thng itself’ (a photographic image) then the result is FAPP, nill, just usenet typing and meaningless. Let the bit-twi8ddler have their way; it has nothing to do with compelling imagery.

Aw gee, you meant the ‘artistic critics’ judging my photos’ ‘technical merit’ have been wrong? It’s really the image that counts?

They may have been wrong, or they may have been right. The only way to know would be to see some of your pix.

I am biased in favor of people who bring real names, as well as real photographs, to the table. The others, I agree with Robert, are just so much blather.

Well sorry about that, but when I started using the group I used a real name and real email and receivedso much SPAM that I had to change addys.

As for the pics, I’ve linked many of them in past posts.

My comment was more sarcasm about ‘judges’ and overblown reliance on ‘technical’ rather then the visual conveyance of beauty and emotion.
J
jaSPAMc
Apr 10, 2009
Mike Russell found these unused words:

On Thu, 09 Apr 2009 19:29:37 -0500, John J wrote:

Mike, what would you like? URLs to digital representations of pictures?

Sounds fine.

Best, as images are not part of non-binary NG’s.

BTW, just to fill in a little bit, Rien and I have had this discussion before. His name is a play on the words "ca ne fait rien" meaning, "that doesn’t matter at all". He is tickled, a little, when people recognize the pun.

also used "Sailor Vea" <G>
E
erpy
Apr 10, 2009
Mike Russell ha scritto:
On Fri, 10 Apr 2009 00:57:50 +0200, erpy wrote:

Oh, and BTW, the digital photography argument would be too painful for users like you to take on.
That’s because it would show you both why you don’t notice much difference between an 8bit and a 16bit photo and at the same time how you’re being ripped off for good even with the most expensive camera on the whole market. (well, *maybe* excluding top-of-the-line Hasselblads)

I think you, and to be fair many others, are making the simplest of tautologies: "more bits is more better". Your discussion of an 8 bit gradient versus a 16 bit gradient can be equally well applied to a 16 bit gradient versus a 32 bit gradient, 32 bit and 64 bit, and so on. As Buzz Lightyear says, "to infinity, and beyond!".

Right, there’s no limit to mathematical "precision". The so called "Real" numbers are like that.

At some point, I’m sure you will agree, the number of bits becomes "lost in the noise".For a photograph, the bedrock of whether this reasoning is valid or not should be in the form of an image that shows the effect. For a computer generated gradient, there is no noise, and therefore the tautology holds in Buzz Lightyear.

That’s where your "problem" is… you take noise for granted. That’s the other argument about digital photography you’d be shocked about.

My challenge, which still stands, is to present a photographic image, in a normal color space such as sRGB or Adobe RGB, that edits better in 8 bit than 16 bit. Do you have one, or not? That’s all, very simple.

The challenge is for a photo that *edits* better ? Like anything goes within Photoshop without plugins except Camera Raw ? That’d be very easy… don’t put any money on the table for your challenge! ;))

Each of the above are easily demonstrated using *photographic images*. But ah, according to you (and to be fair, others), variation of image quality versus bit depth is blazingly obvious. But, unlike the above seven examples, it is not so obvious that you can point to an example photograph, just a computer generated gradient which d nothing to do with nothing.

Do you actually know how digital sensors in a camera work ? Sensors actually *capture* and *store* *1/3rd* of the data needed for an RGB image. The rest is "interpolated".
As a similitude, would you run "precision" tests on a "length measure" taken by hand (i.e. the sensor of a digital camera) or on a measure taken with a laser beam (i.e. a computer-generated image) ? Although, as I said, 16 bits *editing* superiority is easily shown on digital photos as well. The principle stays the same… have many blending layers on your picture and see the difference. Obviously, the more noise you have, the less the difference… but that’s only because the source data is crap from the very beginning (your… anyone’s crap, noisy digital sensor).

I wouldn’t use such a picture for anything anyway.

Not mentioning, the 16 bits in raw photos have a different meaning than "precision". The bit-depth is used to expand the dynamic range of a picture. Hence if you take a raw photo and open it straight in Photoshop without touching anything within Camera Raw, you’re loosing so much "lighting" data you probably have no clue about.
While, strange enough for you, I imagine, all the image processing taking place within Camera Raw is at 16 bits/pixel – despite the fact you can import at 8bits then.

Why, according to your belief, Adobe would waste so much memory and speed by processing photos at 16bits when 8 bits would be more than enough ? Answer: for all the good reasons I said. :))

(oh well, and why most of the raw-dedicated image processors around are featuring 32bit floating point precision, spending money and effort on this ? Just for the sake of a magic marketing word ? Not this time around.)

J
Joel
Apr 10, 2009
Mike Russell wrote:

On Thu, 09 Apr 2009 22:38:57 -0500, Joel wrote:

May be I have everything in backwards, and that’s why I sometime switch to 16-mode to work on low-rez image. And I only use low-rez for DVD label.

You may find that you like the results better – sharper lines, etc – if you change the ppi in Image Size, and work on a higher resolution image. When you’re done, resample back down to the original size using Bi-cubic Sharpen.

No, I never care to change PPI, but I increase number of pixel by switching from 8-bit to 16-bit and if the photo is way too small (like 50-100K) then I may combine with the Image Enlargement tecnique.

That’s it! the photo ain’t important but I just want to have a little better print on the DVD.
MR
Mike Russell
Apr 10, 2009
On Fri, 10 Apr 2009 22:48:03 +0200, erpy wrote:

(Note: For those who may not want to read everything that appears below, I will mention erpy provides no examples to substantiate the claim that photographs edit better in 16 bits than 8 bits. – Mike Russell) …..
That’s where your "problem" is… you take noise for granted. That’s the

Thanks for your concern. I do think your comments are substantial enough to deserve individual replies.
….
The challenge is for a photo that *edits* better ? Like anything goes within Photoshop without plugins except Camera Raw ? That’d be very easy… don’t put any money on the table for your challenge! ;))
….
I have, in the past, put money on the table, and paid up. The results were less than conclusive, due to poor design of the challenge on my part. It’s actually fairly difficult to set the challenge up fairly and clearly.

I paid out the reward, but did not end up with an example of an image that edited better in 8 bits than 16 bits. This is the main reason that I am confident that you cannot provide such an example.
….
Do you actually know how digital sensors in a camera work ? Sensors actually *capture* and *store* *1/3rd* of the data needed for an RGB image. The rest is "interpolated".

Yes, I do. You’re talking about the Bayer pattern. It is inaccurate to say that the sensors capture 1/3 of the data. Luminance data, which is what the eye is most sensitive to, is not interpolated. Chroma data is, to a certain extent. Our eyes do the same thing.

As a similitude, would you run "precision" tests on a "length measure" taken by hand (i.e. the sensor of a digital camera) or on a measure taken with a laser beam (i.e. a computer-generated image) ?

This doesn’t fly from a practical standpoint. My concern is with photographs, and not with manipulating arrays of numbers. This is one reason I reject histograms as a meaningful measure of image quality.

Although, as I said, 16 bits *editing* superiority is easily shown on digital photos as well.

Yackity yackity – if it’s "easy", why not do so? I suggest it is because it is not easy to do so, and may well be impossible, even with extreme editing after the fact.

The principle stays the same…

You can demonstrate a principle using numbers and conclude that "more bits is more better". Whether that principle translates to effective practice is another question, and it’s the one that

have many blending layers on your picture and see the difference.

Fine. This isn’t global warming or world hunger we’re talking about, it’s a psd file with some layers in it. So point us to an example? Until you do so, I suggest you cannot do so, and that you are blowing smoke and mirrors, with Toto about to pull the curtain away.

Obviously, the
more noise you have, the less the difference… but that’s only because the source data is crap from the very beginning (your… anyone’s crap, noisy digital sensor).

Reality has a way of messing up theoretical principles, doesn’t it? LOL.

I wouldn’t use such a picture for anything anyway.

Not all of us have that luxury.

Not mentioning, the 16 bits in raw photos have a different meaning than "precision". The bit-depth is used to expand the dynamic range of a picture.

It’s probably more accurate to say that the additional bits (typically 12) from the camera sensor can be manipulated in Camera Raw. I would agree that access to this data can be beneficial, but that’s not the same as saying that working in 16 bits (or 32) will give a result that is better or different than working in 8 bits. The only thing that will demonstrate that is an example of an actual photograph.

Hence if you take a raw photo and open it straight in Photoshop without touching anything within Camera Raw, you’re loosing so much "lighting" data you probably have no clue about.

Right – again no example though. See a pattern here?

While, strange enough for you, I imagine, all the image processing taking place within Camera Raw is at 16 bits/pixel – despite the fact you can import at 8bits then.

I have no problem with any of this. What I have a problem with is the religious belief that working in 16 bit instead of 8 bit in Photoshop confers any demonstrable advantage.

Why, according to your belief, Adobe would waste so much memory and speed by processing photos at 16bits when 8 bits would be more than enough ? Answer: for all the good reasons I said. :))

I’ve been in computer graphics for quite a while – 25 years or more, and am well aware of the trade-offs of performance and accuracy. Curvemeister uses floating point internally everywhere, and in some cases I believe I get a more accurate, smoother result than Photoshop does.

With today’s processors, 8, 16, and even 32 bit ints are processed at about the same speed. In the early days of computer graphics, the idea of doing a floating divide per pixel was a show stopper, and that was when a megapixel image drew oohs and ahhs at SIGGRAPH.

(oh well, and why most of the raw-dedicated image processors around are featuring 32bit floating point precision, spending money and effort on this? Just for the sake of a magic marketing word ? Not this time around.)

This sums up your argument, I believe. If 8 bits were enough, why would the big companies even bother with 16 and 32 bits. One reason, I believe, is because they can. Another is dynamic range, as you said. But none of this addresses my request that you provide an example of a photographic image that edits better in 16 bits than 8 bits.

Getting back to my original point about examples. Great piles of words are meaningless if there are no examples to back them up. Yet the words grow and grow, with no photograph to back them up. Just a feeling that 16 bits must be better than 8 bits.

If it were as easy to find such an example as you claim it is, it should take you less time to find one than to read, and perhaps, this rather long post.

All the best to you,

Mike Russell – http://www.curvemeister.com
JJ
John J
Apr 10, 2009
Sir F. A. Rien wrote:

I am biased in favor of people who bring real names, as well as real photographs, to the table. The others, I agree with Robert, are just so much blather.

How in the world can we bring real photographs to the digital table? This is an entirely impoverished format.
JJ
John J
Apr 10, 2009
If I dropped as many bits from my posts as bits are dropped from 4×5" negatives, you could not possibly understand the message.

That’s how it is here with images at this time.

Digital sucks.
MR
Mike Russell
Apr 11, 2009
On Fri, 10 Apr 2009 18:50:11 -0500, John J wrote:

How in the world can we bring real photographs to the digital table? This is an entirely impoverished format.

Links to a web page, I guess. Or do you mean "real" as in cow hoofs and silver?

Mike Russell – http://www.curvemeister.com
E
erpy
Apr 11, 2009
Mike Russell ha scritto:
This sums up your argument, I believe. If 8 bits were enough, why would the big companies even bother with 16 and 32 bits. One reason, I believe, is because they can. Another is dynamic range, as you said. But none of this addresses my request that you provide an example of a photographic image that edits better in 16 bits than 8 bits.

Getting back to my original point about examples. Great piles of words are meaningless if there are no examples to back them up. Yet the words grow and grow, with no photograph to back them up. Just a feeling that 16 bits must be better than 8 bits.

If it were as easy to find such an example as you claim it is, it should take you less time to find one than to read, and perhaps, this rather long post.

All the best to you,

I’ve done my homework long ago…. I don’t see why I should do yours too. Take a photograph with some out of focus area, import at 16bits from Camera Raw, duplicate the photo a couple of times and set those layers to Overlay.
View one channel at a time, R, G or B and switch to 8bit…. banding all around in the out of focus area (despite the noise).
Switch back history to 16bits…it’s all gone.

Are you afraid of doing it by yourself and discover that actually you destroyed a lot of data in your pictures by editing at 8bits ? I don’t have to convince you of anything, I know my stuff – plus, I don’t do others’ homework. 🙂

You’re more than free to keep editing your 14bit+ photos using 8bits mode. The pictures aren’t mine in the end. :))
JJ
John J
Apr 11, 2009
erpy wrote:

I’ve done my homework long ago…. I don’t see why I should do yours too. Take a photograph with some out of focus area, import at 16bits from Camera Raw, duplicate the photo a couple of times and set those layers to Overlay.
View one channel at a time, R, G or B and switch to 8bit…. banding all around in the out of focus area (despite the noise).
Switch back history to 16bits…it’s all gone.

Under what circumstances would a person have to do that to a photograph?
D
Dave
Apr 11, 2009
erpy wrote:

I’ve done my homework long ago…. I don’t see why I should do yours too. Take a photograph with some out of focus area, import at 16bits from Camera Raw, duplicate the photo a couple of times and set those layers to Overlay.
View one channel at a time, R, G or B and switch to 8bit…. banding all around in the out of focus area (despite the noise).
Switch back history to 16bits…it’s all gone.

Are you afraid of doing it by yourself and discover that actually you destroyed a lot of data in your pictures by editing at 8bits ? I don’t have to convince you of anything, I know my stuff – plus, I don’t do others’ homework. 🙂

You’re more than free to keep editing your 14bit+ photos using 8bits mode. The pictures aren’t mine in the end. :))

talk talk talk … erpy, how on earth can anyone keep on making a fool of himself the way you do? Without even realizing it?
This started being a very interesting
thread; only until it became obvious how desperately you try to win by talk talk talk without the simple prove requested by Mike. How does it feel to a mannerless fool like you
losing an argument to an gentleman like Mike?
No class at all:-(
E
erpy
Apr 11, 2009
John J ha scritto:
erpy wrote:

I’ve done my homework long ago…. I don’t see why I should do yours too.
Take a photograph with some out of focus area, import at 16bits from Camera Raw, duplicate the photo a couple of times and set those layers to Overlay.
View one channel at a time, R, G or B and switch to 8bit…. banding all around in the out of focus area (despite the noise). Switch back history to 16bits…it’s all gone.

Under what circumstances would a person have to do that to a photograph?

Under what circumstances one could not ?
If you give me your favourite editing test, I’d apply yours…. until then… it’s a test.
E
erpy
Apr 11, 2009
Dave ha scritto:
erpy wrote:

I’ve done my homework long ago…. I don’t see why I should do yours too. Take a photograph with some out of focus area, import at 16bits from Camera Raw, duplicate the photo a couple of times and set those layers to Overlay.
View one channel at a time, R, G or B and switch to 8bit…. banding all around in the out of focus area (despite the noise).
Switch back history to 16bits…it’s all gone.

Are you afraid of doing it by yourself and discover that actually you destroyed a lot of data in your pictures by editing at 8bits ? I don’t have to convince you of anything, I know my stuff – plus, I don’t do others’ homework. 🙂

You’re more than free to keep editing your 14bit+ photos using 8bits mode. The pictures aren’t mine in the end. :))

talk talk talk … erpy, how on earth can anyone keep on making a fool of himself the way you do? Without even realizing it?
This started being a very interesting
thread; only until it became obvious how desperately you try to win by talk talk talk without the simple prove requested by Mike. How does it feel to a mannerless fool like you
losing an argument to an gentleman like Mike?
No class at all:-(

Well, now this "mannerless" fool requires *proof* from Mike, and made by himself.

Dave, eat your tongue next time you call someone a fool without knowing him… who’s the mannerless here ? Did I insulted anyone, or you or Mike ? You just did actually. Proof of you being an uneducated punk.

MR
Mike Russell
Apr 11, 2009
On Sat, 11 Apr 2009 20:12:07 +0200, erpy wrote:

Well, now this "mannerless" fool requires *proof* from Mike, and made by himself.

I would not say you are mannerless at all, quite the contrary. It’s not possible to prove a negative, as you surely know.

I would agree with Dave and others that, given that 16 bit files are double the size of 8 bit, the burden of proof should be on those who believe there is a visible advantage when it comes to manipulating an ordinary photograph.

It’s not enough simply to prove that an image can represent more than 8 bits of data. That’s what’s called a tautology. Some sort of example of its practical usefulness for a normal sRGB or Adobe RGB (or similar space) image ought to be forthcoming, before we all decide to double our file size.

I provided seven examples of image quality issues that are easily proven. Why is 16 bit so different that there are no examples easily at hand? I suggest it is because there are no such examples, or at least, it seems, none from you.

Hand waving, proof by vigorous assertion, and personal criticism of my abilities as a photographer, are not substitutes for an example. —
Mike Russell – http://www.curvemeister.com
E
erpy
Apr 11, 2009
Mike Russell ha scritto:
On Sat, 11 Apr 2009 20:12:07 +0200, erpy wrote:

Well, now this "mannerless" fool requires *proof* from Mike, and made by himself.

I would not say you are mannerless at all, quite the contrary. It’s not possible to prove a negative, as you surely know.

I would agree with Dave and others that, given that 16 bit files are double the size of 8 bit, the burden of proof should be on those who believe there is a visible advantage when it comes to manipulating an ordinary photograph.

It’s not enough simply to prove that an image can represent more than 8 bits of data. That’s what’s called a tautology. Some sort of example of its practical usefulness for a normal sRGB or Adobe RGB (or similar space) image ought to be forthcoming, before we all decide to double our file size.

I provided seven examples of image quality issues that are easily proven. Why is 16 bit so different that there are no examples easily at hand? I suggest it is because there are no such examples, or at least, it seems, none from you.

Hand waving, proof by vigorous assertion, and personal criticism of my abilities as a photographer, are not substitutes for an example.

Mike, what do you think about the image I attached to my previous post then ?
I don’t mean to force anyone to leave 8bits and go 16. If one can’t notice the difference between the two it most probably means he doesn’t need 16bits.

My point is that, it is mathematical truth that editing at 16bits is superior – regardless if a user will perceive *the inevitable loss* using 8bits in his specific environment/application, or not. So, in the end, whether this loss at 8bits is "good enough" or "not perceivable" it’s entirely subjective, although I think I provided a simple editing scenario where rounding errors are even visible with only 2 layers on top of the original photo.

A small trivia for you: do you know why even a 50-bucks graphic card renders pixels at 128bit floating point precision, instead of 24 ?

E
erpy
Apr 11, 2009
Mike Russell ha scritto:
On Sat, 11 Apr 2009 20:12:07 +0200, erpy wrote:

Well, now this "mannerless" fool requires *proof* from Mike, and made by himself.

I would not say you are mannerless at all, quite the contrary. It’s not possible to prove a negative, as you surely know.

It surely is possible to prove "equality" though. Take a 16bit source photo, make some extreme editing at 16bits, convert, without flattening, at 8bits – compare if they’re equal or not.

I would agree with Dave and others that, given that 16 bit files are double the size of 8 bit, the burden of proof should be on those who believe there is a visible advantage when it comes to manipulating an ordinary photograph.

If you *edit* at 16bits and then flatten to 8bits then the error is mitigated – most probably because Photoshop is optimizing the conversion. If you edit at 8bits, the error is all there.

I provided seven examples of image quality issues that are easily proven. Why is 16 bit so different that there are no examples easily at hand?

I did…

MR
Mike Russell
Apr 11, 2009
On Sat, 11 Apr 2009 21:01:02 +0200, erpy wrote:

Mike, what do you think about the image I attached to my previous post then ?

Thanks for trying. This is a non-binary group, so attachments get discarded. If you email it to me, I can give it a home on my web site so others can check it out.

My point is that, it is mathematical truth that editing at 16bits is superior

I don’t question the theory. It amounts to 16 is greater than 8, and I accept that. I seek an example photograph that shows that more than 8 bits is of any practical use, no matter how perceptive one may be. Again, I’m talking about a color photograph in a standard color space such as sRGB or Adobe RGB.

I’ll bet Rubles to raisins that your image, come what may, will be a contrived image in some way

So, in the end, whether this loss at 8bits is "good enough" or "not perceivable" it’s entirely subjective, although I think I provided a simple editing scenario where rounding errors are even visible with only 2 layers on top of the original photo.

The layer example is of interest. I did try your earlier example, and if the photograph is similar I will have some comments about it.

A small trivia for you: do you know why even a 50-bucks graphic card renders pixels at 128bit floating point precision, instead of 24 ?

Because, being part of objective reality, and not an abstraction, the signal contains analog noise.

Mike Russell – http://www.curvemeister.com
MR
Mike Russell
Apr 11, 2009
On Sat, 11 Apr 2009 21:22:17 +0200, erpy wrote:

It surely is possible to prove "equality" though. Take a 16bit source photo, make some extreme editing at 16bits, convert, without flattening, at 8bits – compare if they’re equal or not.

It would be possible to perform an edit that left an image in the bottom 8 bits of a 16 bit image. Converting to 8 bits would result in a black image. Likewise, a 32 bit image could contain a 16 bit image in the bottom two bytes of each channel, and so on for 64, 128. Does it follow, then, that each increase in precision makes for a better image, or an easier to edit image? Of course not.

This is the Buzz Lightyear "to infinity and beyond" argument. It is deficient because it lacks an example of a photograph that edits better in 16 bits. It’s not just you. Everyone who promotes 16 bit editing does so based on a warm fuzzy feeling about more bits is better. I have a lot of respect for many of these people – the ones who take excellent photographs, and *especially* the ones who are customers of mine.

Every once in a while, I like to rock the boat and ask one of the people who promotes this point of view for an example of an image that does better.

Mike Russell – http://www.curvemeister.com
E
erpy
Apr 11, 2009
Mike Russell ha scritto:
On Sat, 11 Apr 2009 21:01:02 +0200, erpy wrote:

Mike, what do you think about the image I attached to my previous post then ?

Thanks for trying. This is a non-binary group, so attachments get discarded. If you email it to me, I can give it a home on my web site so others can check it out.

I see, I will send it to you then.

A small trivia for you: do you know why even a 50-bucks graphic card renders pixels at 128bit floating point precision, instead of 24 ?

Because, being part of objective reality, and not an abstraction, the signal contains analog noise.

By "renders" I mean calculates, processes… as when you lay down several layers in Photoshop and you see the result of all the operations on all visible layers and effects, in the current "image window". So, no, it’s not that…and the signal is digital. Graphic cards now only output in DVI and/or HDMI standard digital signals.

The question, and the right answer, is clearly related to our debate. At the beginning 3d cards used 32bit RGBA processing, i.e. 8bits/component. At that times whenever many polygons were layered on screen at the same time banding was inevitable and very noticeable. (imagine, for example, 10+ explosion effects one on top of each other…or many semi-transparent objects and so on)
That is exactly the difference between image processing at 32bits and at 128bits… today you don’t see banding anymore on games because rendering is taking place at 32bit/component floating point precision, thus resulting in a correct blending.
It doesn’t matter if the output is still 24bits/pixel (although DVI dual link and HDMI reach a maximum of 48bit/pixel digital output). It’s the processing precision that matters. If the numerical rounding takes place in-between operations, it accumulates rapidly and the net final effect is that more and more adjacent pixels are set to the same color/value – hence the banding.

This is true for any layered image processing where pixels are blended in some way… and thus it holds true in Photoshop as well.

E
erpy
Apr 11, 2009
Mike Russell ha scritto:
On Sat, 11 Apr 2009 21:22:17 +0200, erpy wrote:

It surely is possible to prove "equality" though. Take a 16bit source photo, make some extreme editing at 16bits, convert, without flattening, at 8bits – compare if they’re equal or not.

It would be possible to perform an edit that left an image in the bottom 8 bits of a 16 bit image. Converting to 8 bits would result in a black image. Likewise, a 32 bit image could contain a 16 bit image in the bottom two bytes of each channel, and so on for 64, 128.

I was asking for proving equality though. You’ve described a simple trick that would easily prove my point…but I didn’t asked for that…I asked for some repeatable test for proving *your* point. You simply need to exhibit a "difference image" of the result of both edits, 16 and 8 bits.
Once you have both images done and layers flattened and all effects rasterized if any, convert the 8bit result to 16bits – nothing changes obviously, it just brings it to the same depth for comparison. Open both results in HDRShop, which performs 96bit/pixel floating point calculations, and subtract one image from the other. You now have a difference image…which, according to your point, should be black –
i.e. all pixels = 0,0,0

If it’s not, then you have lost something. The more pixels you can actually see from the difference image, the more data you lost at 8bits, comparing to 16.
HDRShop also has the ability to make the sum of all pixel values in the entire image. If you sum up all the pixels in that difference image and divide that number by the number of pixels, you get the mean error – and that’s it for the objective "equality" test.

MR
Mike Russell
Apr 11, 2009
On Sun, 12 Apr 2009 00:22:05 +0200, erpy wrote:

This is true for any layered image processing where pixels are blended in some way… and thus it holds true in Photoshop as well.

You are conflating two different universes. In the world of Photo-realistic rendering, with checkerboards, Rob Cook’s rendered metallic teapots, and crystal spheres going off to infinity (and beyond), yes, floating point precision is a necessity, not an option. You may have gathered, surely by now, that this is not the world I’m talking about. As complex as computer graphics is, it remains an idealized approximation to the real world. IOW, it’s not real.

The world of photography is real. It is in the trenches, using physical cameras to capture light from physical objects, and real printers with actual human beings who view the images. It is constrained by the realities of physics of light, electronics, pigment, cognition, and physiology. With ambient light reflecting the camera, is more like a VGA video card than a pure digital one. Real, physical lenses that diffract, diffuse, and flare, and real printers, monitors, and most important of all, real eyeballs that are looking at the image.

Taken in its totality, reality is a much more complex world than the world of CGI. CGI can be thought of as simply a way to verify the accuracy of our assumptions about how light and perception really work. We have a long way to go, as I’m sure you would agree.

In the real world, "this" world, I maintain, an 8 bit color photo using a normal color space provides more than enough headroom for severe edits, and 16 bits provides no advantage. If you disagree, and maintain that it is trivial to prove otherwise with an example image, I, and the world, await you.

Mike Russell – http://www.curvemeister.com
E
erpy
Apr 11, 2009
Mike Russell ha scritto:
On Sun, 12 Apr 2009 00:22:05 +0200, erpy wrote:

This is true for any layered image processing where pixels are blended in some way… and thus it holds true in Photoshop as well.

You are conflating two different universes. In the world of Photo-realistic rendering, with checkerboards, Rob Cook’s rendered metallic teapots, and crystal spheres going off to infinity (and beyond), yes, floating point precision is a necessity, not an option. You may have gathered, surely by now, that this is not the world I’m talking about. As complex as computer graphics is, it remains an idealized approximation to the real world. IOW, it’s not real.

The world of photography is real. It is in the trenches, using physical cameras to capture light from physical objects, and real printers with actual human beings who view the images. It is constrained by the realities of physics of light, electronics, pigment, cognition, and physiology. With ambient light reflecting the camera, is more like a VGA video card than a pure digital one. Real, physical lenses that diffract, diffuse, and flare, and real printers, monitors, and most important of all, real eyeballs that are looking at the image.

Taken in its totality, reality is a much more complex world than the world of CGI. CGI can be thought of as simply a way to verify the accuracy of our assumptions about how light and perception really work. We have a long way to go, as I’m sure you would agree.

In the real world, "this" world, I maintain, an 8 bit color photo using a normal color space provides more than enough headroom for severe edits, and 16 bits provides no advantage. If you disagree, and maintain that it is trivial to prove otherwise with an example image, I, and the world, await you.

That is right, till when you begin *editing* the digital "capture". At that point, blending precision holds true.
As soon as you "touch" the source data, you enter the realm of image processing math, which includes numerical precision and error.

I’m sending you the photo editing test. The photo isn’t mine, I found it on a website that "donates" raw samples… thus you might probably have seen this picture before, and I disclaim any use of such a photo. If I remember well the source was http://www.rawsamples.ch/ … but I might be wrong.

In the archive you will find:

– whole view of the original photo
– PSD of an edited crop at 16bit, with layers
– BMP of the 8bits result of the edited crop

E
erpy
Apr 11, 2009
Finally, let me make clear how "banding" works. Banding occurs when _numerical rounding_ (error) takes place on adjacent pixels, with low-spaced values (smooth gradient/signal), thus setting those adjacent pixels to the same value. (it does include "fine noise" as well)

Practical example. Say you have source pixels in one of the RGB channels set to the following values, at 8bit (0,255):
(I divide "bands" with "|")

127,127|126,126|125,125|124,124
(4 groups of pixels at 4 different values.. i.e. 4 "bands" 2 pixels "wide")

Say you have a layer that multiplies by 0.5 (50%) – i.e. it halves the brightness. The pixels become:

63,63,63,63|62,62,62,62

Result: 2 bands, 4 pixels wide… more visible. Put another multiplying layer, again half brightness, on top of the resulting pixels…you’d have:

31,31,31,31,31,31,31,31

Result: 1 band, 8 pixels wide…. all the source pixels now have the same value. Pretty bad. You’ve _lost_ exactly 7/8 (87%) of the original data.
(btw, you get the same rounded values if you multiply directly by 0.25 == 0.5*0.5)

There’s little you can do about that… except editing at a higher bit-depth of course.
Photoshop might compensate banding artifacts at 8bits with some dithering, but I haven’t tested it for that – it looks like it doesn’t at a first glance.

I hope you get the importance of editing at 16bits now.

JJ
John J
Apr 11, 2009
erpy wrote:
John J ha scritto:
erpy wrote:

I’ve done my homework long ago…. I don’t see why I should do yours too.
Take a photograph with some out of focus area, import at 16bits from Camera Raw, duplicate the photo a couple of times and set those layers to Overlay.
View one channel at a time, R, G or B and switch to 8bit…. banding all around in the out of focus area (despite the noise). Switch back history to 16bits…it’s all gone.

Under what circumstances would a person have to do that to a photograph?

Under what circumstances one could not ?
If you give me your favourite editing test, I’d apply yours…. until then… it’s a test.

With respect I must ask if you think any photograph would be susceptible to editing to the extreme suggested in the post above. If you have such a candidate, then post ther URL

Thank you,
j
E
erpy
Apr 12, 2009
John J ha scritto:
erpy wrote:
John J ha scritto:
erpy wrote:

I’ve done my homework long ago…. I don’t see why I should do yours too.
Take a photograph with some out of focus area, import at 16bits from Camera Raw, duplicate the photo a couple of times and set those layers to Overlay.
View one channel at a time, R, G or B and switch to 8bit…. banding all around in the out of focus area (despite the noise). Switch back history to 16bits…it’s all gone.

Under what circumstances would a person have to do that to a photograph?

Under what circumstances one could not ?
If you give me your favourite editing test, I’d apply yours…. until then… it’s a test.

With respect I must ask if you think any photograph would be susceptible to editing to the extreme suggested in the post above. If you have such a candidate, then post ther URL

Thank you,
j

I have made a reasonable test and sent to Mike. He might want to show it somewhere.
It doesn’t matter how "hard" the single layer is… it’s the number of operations that counts in this case. The more operations you do the more banding will occur.
(read my latest post about banding)
The banding worsen even quicker if you "flatten" or save to disk at 24bits and then re-open and keep editing over and over.
That is (also) why professional photographers shoot and edit raw images… because you can re-edit again and again without perceivable loss of data and precision.
JJ
John J
Apr 12, 2009
Someday in the future high resolution will be significant with new monitors and printers, but until then, all this discourse is bullshit.
E
erpy
Apr 12, 2009
John J ha scritto:
Someday in the future high resolution will be significant with new monitors and printers, but until then, all this discourse is bullshit.

What’s resolution got to do with bit-depth ? Banding is somehow related to resolution, but only because you have more pixels to cover with a smooth gradient, using the same number of "shades" per-channel. Otherwise, you can see banding even with small images…it depends by the content of the image itself.
T
Talker
Apr 12, 2009
On Fri, 10 Apr 2009 18:53:07 -0700, Mike Russell
wrote:

On Fri, 10 Apr 2009 18:50:11 -0500, John J wrote:

How in the world can we bring real photographs to the digital table? This is an entirely impoverished format.

Links to a web page, I guess. Or do you mean "real" as in cow hoofs and silver?

When someone wants to post a picture for the group to see, why not use the group that was created for that…alt.binaries.photoshop? It’s practically empty, and there is no size limit to the post. Anyway, it was just a thought….

Talker
MR
Mike Russell
Apr 12, 2009
On Sun, 12 Apr 2009 01:05:39 +0200, erpy wrote:

That is right, till when you begin *editing* the digital "capture". At that point, blending precision holds true.
As soon as you "touch" the source data, you enter the realm of image processing math, which includes numerical precision and error.

I would like to invite others to join the digital realm, and participate in the experiment using the images erpy has so kindly provided:

http://mike.russell-home.net/tmp/erpy/

Mike Russell – http://www.curvemeister.com
J
jaSPAMc
Apr 12, 2009
Mike Russell found these unused words:

On Sat, 11 Apr 2009 21:22:17 +0200, erpy wrote:

It surely is possible to prove "equality" though. Take a 16bit source photo, make some extreme editing at 16bits, convert, without flattening, at 8bits – compare if they’re equal or not.

It would be possible to perform an edit that left an image in the bottom 8 bits of a 16 bit image. Converting to 8 bits would result in a black image. Likewise, a 32 bit image could contain a 16 bit image in the bottom two bytes of each channel, and so on for 64, 128. Does it follow, then, that each increase in precision makes for a better image, or an easier to edit image? Of course not.

This is the Buzz Lightyear "to infinity and beyond" argument. It is deficient because it lacks an example of a photograph that edits better in 16 bits. It’s not just you. Everyone who promotes 16 bit editing does so based on a warm fuzzy feeling about more bits is better. I have a lot of respect for many of these people – the ones who take excellent photographs, and *especially* the ones who are customers of mine.

Every once in a while, I like to rock the boat and ask one of the people who promotes this point of view for an example of an image that does better.

There’s possibly an analogy in the dgital sound world. Many have switched to 96 kBpS encoding at maximum bit rate, claiming to ‘hear’ the difference – this on Old Time radio shows where the maximum high end is 4,500 Hz and a 40 dB dynamic range.

IMHO, If it’s -=not=- in the original, you don’t need the extra bandwidth and dynamics.

Perhaps some manipulations in PS would benefit from the 32 bits and leave less artifacts – if they could be seen!
JJ
John J
Apr 12, 2009
erpy wrote:

That is (also) why professional photographers shoot and edit raw images… because you can re-edit again and again without perceivable loss of data and precision.

A competent professional doesn’t have to edit in such a manner. He/she knows how to do it right in-camera.
JJ
John J
Apr 12, 2009
Mike Russell wrote:

I would like to invite others to join the digital realm, and participate in the experiment using the images erpy has so kindly provided:

I see it is time for me to resign from this discussion. In an hour I am leaving the house to shoot some 8×10" color film. Enough of the digital.
MR
Mike Russell
Apr 12, 2009
On Sun, 12 Apr 2009 10:33:46 -0500, John J wrote:

I see it is time for me to resign from this discussion. In an hour I am leaving the house to shoot some 8×10" color film. Enough of the digital.

An 8×10 chrome, or any piece of film that size is no small potatoes these days. Hat’s off to you!

Mike Russell – http://www.curvemeister.com
E
erpy
Apr 12, 2009
John J ha scritto:
erpy wrote:

That is (also) why professional photographers shoot and edit raw images… because you can re-edit again and again without perceivable loss of data and precision.

A competent professional doesn’t have to edit in such a manner. He/she knows how to do it right in-camera.

By reading many "pro" forums I’d say they want to be able to get as many "good" versions as they can…so their clients can choose their fav. Artistically, I can see re-editing as a good occasion to experiment with different "moods" of a photo. (it’s not just "getting it right")
E
erpy
Apr 12, 2009
Mike Russell ha scritto:
On Sun, 12 Apr 2009 01:05:39 +0200, erpy wrote:

That is right, till when you begin *editing* the digital "capture". At that point, blending precision holds true.
As soon as you "touch" the source data, you enter the realm of image processing math, which includes numerical precision and error.

I would like to invite others to join the digital realm, and participate in the experiment using the images erpy has so kindly provided:
http://mike.russell-home.net/tmp/erpy/

Yes, Mike reported exactly the experiment.
The fact he wasn’t noticing the banding at first was because Photoshop conversion engine was applying dithering to it – as he reports in his webpage.

As I said to Mike, dithering does mitigate banding – although you can see it on each RGB channel, individually – but the real data you’re left with for subsequent editing is the one shown in the BMP found on the page… which suffers from severe banding (i.e. loss of data). This is a delicate issue we must not underestimate, _the same loss is in the dithered version as well_ since the reduced range of colors stays the same. Dithering only introduces algorithmic noise in order to trick human perception. (again, if that’s good for someone, fair enough…)

Now, it’s up to you. I gave evidence of the fact that editing a source image/photo at 8bits produces loss of data and its severity is proportional to the number of layers modifying the original data. If you can live with it, keep editing at 8bits… if you want to be sure you’re not losing too much data and details, edit at 16bits. (at least)

JJ
John J
Apr 13, 2009
Just what kind of photograph has the kind of gradient that suffers from rounding errors? I don’t find many perfect gradients in reality, not even in a well graduated sky.

How likely is a photograph to require such severe edits that banding will occur? Who in the world has to iteratively rotate an image several times?
JJ
John J
Apr 13, 2009
erpy wrote:
John J ha scritto:
erpy wrote:

That is (also) why professional photographers shoot and edit raw images… because you can re-edit again and again without perceivable loss of data and precision.

A competent professional doesn’t have to edit in such a manner. He/she knows how to do it right in-camera.

By reading many "pro" forums I’d say they want to be able to get as many "good" versions as they can…so their clients can choose their fav.

Shit, then they don’t have to do the photo until the client makes up some image specifications. It’s all made up.

Artistically, I can see re-editing as a good occasion to experiment with different "moods" of a photo. (it’s not just "getting it right")

Usually, after a hundred traumatic edits one realizes he could have done it with far fewer and starts over for smoother results.
JJ
John J
Apr 13, 2009
Mike Russell wrote:
On Sun, 12 Apr 2009 10:33:46 -0500, John J wrote:

I see it is time for me to resign from this discussion. In an hour I am leaving the house to shoot some 8×10" color film. Enough of the digital.

An 8×10 chrome, or any piece of film that size is no small potatoes these days. Hat’s off to you!

It did not go too well. It was quite windy. I should have brought the heavy steel monster rather than the Deardorff. At least the bridge didn’t sway.

(I’m sure someone will tell me there is an anti-wind plug-in, or spout some brainstorm using motion-blur (anti-motion?). 🙂 )
E
erpy
Apr 13, 2009
John J ha scritto:
Just what kind of photograph has the kind of gradient that suffers from rounding errors? I don’t find many perfect gradients in reality, not even in a well graduated sky.

How likely is a photograph to require such severe edits that banding will occur? Who in the world has to iteratively rotate an image several times?

John, this is not "an accident". We’re not measuring "how many times it happens"…. it just happens all the times.
The point is, how much you accept the result. If you do accept to have a dithered result of your editing (all the times), you’re done…. you can perfectly live with it.
As I said, even a single multply layer will double the banding… but when Photoshop dithers the result you can’t notice it too much. Although, colors aren’t there anymore. (loss of data)

So, consequences to this fact are entirely subjective.
People who decide they always want to keep their original "colors", all of them, and keep smooth gradients, and re-edit without severe losses, will edit at 16bit+… people who can set for "visually acceptable" will continue editing at 8bit.
MR
Mike Russell
Apr 13, 2009
I differ on some of erpy’s assumptions, and my fingers are twitching a bit when I read some of what he’s saying.

I’m bowing out of the conversation for the next day or two, to give others a chance to chime in and perhaps try out the example image that erpy provided.
http://mike.russell-home.net/tmp/erpy/


Mike Russell – http://www.curvemeister.com

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