Photoshop CS – 15-bit 16-bit mode.

wrote in message news:…

16-bit mode is actually 15-bit (maximum values are 32,767), according to the Info tool.

Is this internal, or a bug in the Info tool?

As Mr Cox will be delighted to inform you, Photoshop’s "16"-bit mode is indeed quasi-15-bit, channels have an internal range of 0-32768 (inclusive). See this recent discussion on Adobe Forums: http://www.adobeforums.com/cgi-bin/webx?128@251.AEDHczu4wcs. 8@.3bb3f466

Adobe does not seem to consider it a bug, but those who need to work with 16 bit data may disagree.

T

In article , wrote:

16-bit mode is actually 15-bit (maximum values are 32,767), according to the Info tool.

Is this internal, or a bug in the Info tool?

32767 is 16-bit signed integer max. I wonder what they use the <0 values for.

Who said it was signed?

The range is 0 to 32768.

Chris

In article , jjs
wrote:

In article , wrote:

16-bit mode is actually 15-bit (maximum values are 32,767), according to the Info tool.

Is this internal, or a bug in the Info tool?

32767 is 16-bit signed integer max. I wonder what they use the <0 values for.

In article <160520041717368533%>, Chris Cox
wrote:

Who said it was signed?

Not me. I only set the bait.

The range is 0 to 32768.

And that’s plenty.

(jjs) wrote in message news:…

In article , wrote:

16-bit mode is actually 15-bit (maximum values are 32,767), according to the Info tool.

Is this internal, or a bug in the Info tool?

32767 is 16-bit signed integer max. I wonder what they use the <0 values for.

Photoshop’s quasi-15-bit upper value is +32768, so the 16 bit value is regarded as unsigned. (See Adobe Forums thread cited above.)

T

(jjs) wrote in message news:…

In article , wrote:

16-bit mode is actually 15-bit (maximum values are 32,767), according to the Info tool.

Is this internal, or a bug in the Info tool?

32767 is 16-bit signed integer max. I wonder what they use the <0 values for.

Photoshop’s quasi-15-bit upper value is +32768, so the 16 bit value is regarded as unsigned. (See Adobe Forums thread cited above.)

T

In article ,
(Toby Thain) wrote:

(jjs) wrote in message

news:…

In article , wrote:

16-bit mode is actually 15-bit (maximum values are 32,767), according to the Info tool.

Is this internal, or a bug in the Info tool?

32767 is 16-bit signed integer max. I wonder what they use the <0

values for.

Photoshop’s quasi-15-bit upper value is +32768, so the 16 bit value is regarded as unsigned. (See Adobe Forums thread cited above.)

It wasn’t me who first mentioned 2^16-1. I was just responding to the person who did.

(jjs) wrote in message news:…

In article , wrote:

16-bit mode is actually 15-bit (maximum values are 32,767), according to the Info tool.

Is this internal, or a bug in the Info tool?

32767 is 16-bit signed integer max. I wonder what they use the <0 values for.

Photoshop’s quasi-15-bit upper value is +32768, so the 16 bit value should be regarded as unsigned. (See Adobe Forums thread cited above.)

T

Chris Cox writes:

Who said it was signed?

The range is 0 to 32768.

Which is just beyond a 15-bit unsigned integer. 2^16 was 65,536, last I checked. That said, I don’t know of any digital camera that gives even 15 useful bits, much less 16.

<snip>

—
-Stephen H. Westin
Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors.

Stephen H. Westin wrote:

Chris Cox writes:

Who said it was signed?

The range is 0 to 32768.

Which is just beyond a 15-bit unsigned integer. 2^16 was 65,536, last I checked. That said, I don’t know of any digital camera that gives even 15 useful bits, much less 16.

Yes, but medical data, and CGI data can generate that much data.

There is also the question of dynamic range. Luminance maps (which often use floating point) and other data generated by combining several conventional photographs can easlily use up 15-16 bits of dynamic range.

All that said, yes, for photographs you can’t see much past 8 bits per channel gamma encoded, and our output devices are more limited than our eyes, particularly if you consider that fine art prints are where the money is, not CRT display, but that does not stop some of us from striving for more.
—

Mike Russell
www.curvemeister.com
www.geigy.2y.net

"Mike Russell" wrote in message
SNIP

Yes, but medical data, and CGI data can generate that much data.

Indeed, and changing colorspace, resizing, sharpening, etc. will also use whatever is available to preseve accuracy, until reduction to 8-b/ch.

Bart

westin* (Stephen H. Westin) wrote in message news:…

Chris Cox writes:

Who said it was signed?

The range is 0 to 32768.

Which is just beyond a 15-bit unsigned integer. 2^16 was 65,536, last I checked. That said, I don’t know of any digital camera that gives even 15 useful bits, much less 16.

Who said it was a 15-bit unsigned integer? It’s a 16-bit unsigned field… with an internal maximum less than the implied 65535.

And as for the source of 16-bit data, there are many ways to get it… synthetic renderings, scientific and medical images (as others have mentioned), etc. Many formats offer well beyond 16 bits per channel.

TIFF and SGI formats, to name two common ones, offer full 16 bits per channel.

T

<snip>

(Toby Thain) writes:

westin* (Stephen H. Westin) wrote in message news:…

Chris Cox writes:

Who said it was signed?

The range is 0 to 32768.

Which is just beyond a 15-bit unsigned integer. 2^16 was 65,536, last I checked. That said, I don’t know of any digital camera that gives even 15 useful bits, much less 16.

Who said it was a 15-bit unsigned integer?

Well, I kinda did. It’s 15 bits unsigned, plus one other possible value. A distinction without a difference, as far as the results are concerned.

It’s a 16-bit unsigned
field… with an internal maximum less than the implied 65535.
And as for the source of 16-bit data, there are many ways to get it… synthetic renderings, scientific and medical images (as others have mentioned), etc. Many formats offer well beyond 16 bits per channel.

Definitely true. But I’d bet that well over 99% of the pixels run through Photoshop come from scanners and digital cameras, and are displayed on monitors or paper prints with effective dynamic range within the capability of 8 bits. After all, retouching and alteration aren’t really considered useful things to do to medical imagery…

TIFF and SGI formats, to name two common ones, offer full 16 bits per channel.

Oh, yes. 32-bit float in TIFF, for example.

—
-Stephen H. Westin
Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors.

jjs wrote:

In article , wrote:

16-bit mode is actually 15-bit (maximum values are 32,767), according to the Info tool.

Is this internal, or a bug in the Info tool?

32767 is 16-bit signed integer max. I wonder what they use the <0 values for.

Since most 16-bit material comes from RAW camera images, the question is: are those true 16-bit images and if so, how does Photoshop handle them?

—– Paul J. Gans

Chris Cox wrote:

Who said it was signed?

The range is 0 to 32768.

Chris

This is wrong no matter how it is interpreted. 16 bits can represent 65536 different values. 15 bits can represent 32768. If Photoshop 16-bit mode can only represent 32768 values then it is *not* a 16-bit mode.

On the other hand, if source images such as those from various cameras (Canon, Nikon, etc.) claiming to be 16-bit images only contain 32768 different values, then they are not 16-bit images either, but 15-bit images.

To make matters worse, even if the range is as Chris states it above, there are 32769 values in the range from 0 to 32768.

All in all, I suspect one or many of us have slightly mistated things.

— Paul J. Gans

In article , jjs
wrote:

In article , wrote:

16-bit mode is actually 15-bit (maximum values are 32,767), according to the Info tool.

Is this internal, or a bug in the Info tool?

32767 is 16-bit signed integer max. I wonder what they use the <0 values for.

"Paul J Gans" wrote in message
SNIP

Since most 16-bit material comes from RAW camera images, the question is: are those true 16-bit images and if so, how does Photoshop handle them?

In most cases they are 12-14 bit/channel images, of which approx. 1-2 bits noise. But as soon as you sharpen, convert color profile, etc, you can use all bits the internal engine supports.

Bart

Stephen H. Westin <westin*> wrote:

Chris Cox writes:

Who said it was signed?

The range is 0 to 32768.

Which is just beyond a 15-bit unsigned integer. 2^16 was 65,536, last I checked. That said, I don’t know of any digital camera that gives even 15 useful bits, much less 16.

<snip>

RAW mode in Canon and other cameras and NEF mode in Nikon cameras supposedly produces an image with 16 bits per color channel per pixel.

Camera makers supply software to converst such images to TIFFs (or JPEGS). The user can adjust the ranges converted thus going for shadow detail or highlight detail as they see fit.

I’ve never had reason to doubt that those images did have 16 bits per color channel. Perhaps I should have.

In any event, the practical question is whether to load the RAW or NEF mode image into Photoshop (it will, with Adobe supplied plug-ins, accept either) and do the conversion there or to do the conversion in the manufacturers’ less-capable software.

However if Photoshop is indeed throwing away half the color range….

—- Paul J. Gans

From: Paul J Gans

RAW mode in Canon and other cameras and NEF mode in Nikon cameras supposedly produces an image with 16 bits per color channel per pixel.

I’ve never had reason to doubt that those images did have 16 bits per color channel. Perhaps I should have.

Actually most of the digital cameras output 12 bits/channel or 8 bits/channel, not 16. I have the Canon 10D and 1Ds and both are 12 bits max, even though the files open in 16 bit mode in Photoshop.

Also, many scanners are 12 bit or 14 bit/channel, with some of the newer ones true 16 bits. I think my first film scanner was 12 bits (Nikon LS-2000) and the one I’m using now is 14 bits/channel (LS-8000).

All 10 bit, 12 bit and 14 bit files get saved as if they were 16 bits because it’s easier to pack the data into 2 eight bit bytes, even if they have to fill the upper bits with zeros. These files all open in 16 bit mode in Photoshop but actual data is limited to what the capture device provided. Maybe that’s where you got the idea that all these images actually have 16 bits/channel, but most of them don’t.

I think 12 bits for photographic images is very useful but much beyond that and you’re reaching the point of diminishing returns, based on editing thousands of 8, 12 and 14 bit/channel images.

In any event, the practical question is whether to load the RAW or NEF mode image into Photoshop (it will, with Adobe supplied plug-ins, accept either) and do the conversion there or to do the conversion in the manufacturers’ less-capable software.

They are still 12 bits (at least the Canon RAW files).

However if Photoshop is indeed throwing away half the color range….

LOL … don’t think so 🙂

Bill

From: Paul J Gans

On the other hand, if source images such as those from various cameras (Canon, Nikon, etc.) claiming to be 16-bit images only contain 32768 different values, then they are not 16-bit images either, but 15-bit images.

12 bits/channel … see my other post.

Bart van der Wolf wrote:

"Paul J Gans" wrote in message
SNIP

Since most 16-bit material comes from RAW camera images, the question is: are those true 16-bit images and if so, how does Photoshop handle them?

In most cases they are 12-14 bit/channel images, of which approx. 1-2 bits noise. But as soon as you sharpen, convert color profile, etc, you can use all bits the internal engine supports.

Bart

Ok. Thanks.

—– Paul J. Gans

Bill Hilton wrote:

From: Paul J Gans

RAW mode in Canon and other cameras and NEF mode in Nikon cameras supposedly produces an image with 16 bits per color channel per pixel.

I’ve never had reason to doubt that those images did have 16 bits per color channel. Perhaps I should have.

Actually most of the digital cameras output 12 bits/channel or 8 bits/channel, not 16. I have the Canon 10D and 1Ds and both are 12 bits max, even though the files open in 16 bit mode in Photoshop.

Also, many scanners are 12 bit or 14 bit/channel, with some of the newer ones true 16 bits. I think my first film scanner was 12 bits (Nikon LS-2000) and the one I’m using now is 14 bits/channel (LS-8000).

All 10 bit, 12 bit and 14 bit files get saved as if they were 16 bits because it’s easier to pack the data into 2 eight bit bytes, even if they have to fill the upper bits with zeros. These files all open in 16 bit mode in Photoshop but actual data is limited to what the capture device provided. Maybe that’s where you got the idea that all these images actually have 16 bits/channel, but most of them don’t.

I think 12 bits for photographic images is very useful but much beyond that and you’re reaching the point of diminishing returns, based on editing thousands of 8, 12 and 14 bit/channel images.

In any event, the practical question is whether to load the RAW or NEF mode image into Photoshop (it will, with Adobe supplied plug-ins, accept either) and do the conversion there or to do the conversion in the manufacturers’ less-capable software.

They are still 12 bits (at least the Canon RAW files).

However if Photoshop is indeed throwing away half the color range….

LOL … don’t think so 🙂

Bill

Thanks. I certainly hoped Photoshop wasn’t throwing
any information away.

By the way (I’ve not tried this yet) I assume that one
can save the image using the upper 8 bits out of 12 and
save it again using the lower 8. These two can then
be combinded to give an image having mor detail in
the highlights and the shadows than an ordinary 8 bitter would have. Or am I off-base?

—- Paul J. Gans

westin* (Stephen H. Westin) wrote in message news:…

[…] But I’d bet that well over 99% of the pixels run
through Photoshop come from scanners and digital cameras, and are displayed on monitors or paper prints with effective dynamic range within the capability of 8 bits. After all, retouching and alteration aren’t really considered useful things to do to medical imagery…

Fair enough, but Photoshop still has plenty of conventional "image processing" features – histogramming, filtering, convolutions, format conversions, channel arithmetic – aside from its main use (attaching celebrity heads to anonymous bodies).

Returning to the topic, the fact that it "munges" 16 bit data into a smaller dynamic range is perhaps one of the strongest indications that the program is not really aimed at serious image processing applications.

TIFF and SGI formats, to name two common ones, offer full 16 bits per channel.

Oh, yes. 32-bit float in TIFF, for example.

As well as true 16-bit integer channels. And any HDR image. T

(Bill Hilton) writes:

From: Paul J Gans

On the other hand, if source images such as those from various cameras (Canon, Nikon, etc.) claiming to be 16-bit images only contain 32768 different values, then they are not 16-bit images either, but 15-bit images.

12 bits/channel … see my other post.

from a non-cooled digital camera. Chilled cameras routinely achieve 14 or 15 bits, and I’m sure the proper application of liquid nitrogen can improve on that. But since almost all digital cameras used for general photography are unchilled, 12 bits is the best possible at the moment.

—
-Stephen H. Westin
Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors.

(Toby Thain) writes:

westin* (Stephen H. Westin) wrote in message news:…

<snip>

TIFF and SGI formats, to name two common ones, offer full 16 bits per channel.

Oh, yes. 32-bit float in TIFF, for example.

As well as true 16-bit integer channels. And any HDR image.

Well, the Ward HDR format actually has 8 bits per channel mantissa, with an 8-bit exponent shared among the three channels. So it’s not true 16-bit precision. That’s one of the reasons for OpenEXR, logLUV TIFF, and the like.

—
-Stephen H. Westin
Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors.

"Stephen H. Westin" <westin*> wrote in message

(Bill Hilton) writes:

SNIP

12 bits/channel … see my other post.

from a non-cooled digital camera. Chilled cameras routinely achieve 14 or 15 bits, and I’m sure the proper application of liquid nitrogen can improve on that.

At the risk of wandering too much away from Photoshop ;-): If the camera’s ADC is only 12-bit, even liquid Nitrogen can’t change that…

Bart

"Bart van der Wolf" writes:

"Stephen H. Westin" <westin*> wrote in message

(Bill Hilton) writes:

SNIP

12 bits/channel … see my other post.

from a non-cooled digital camera. Chilled cameras routinely achieve 14 or 15 bits, and I’m sure the proper application of liquid nitrogen can improve on that.

At the risk of wandering too much away from Photoshop ;-): If the camera’s ADC is only 12-bit, even liquid Nitrogen can’t change that…

That’s absolutely correct. But I wasn’t thinking in that direction; I was talking about physical limitations as they stand today. Without cooling, bits beyond 12 (for a DSLR-type sensor) or even 10 (for a consumer-type sensor) will be pretty much pure noise.

—
-Stephen H. Westin
Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors.

12 bits/channel (for Canon and Nikon dSLR’s)… see my other post.

From: westin* (Stephen H. Westin)

from a non-cooled digital camera. Chilled cameras routinely achieve 14 or 15 bits, and I’m sure the proper application of liquid nitrogen can improve on that.

LOL … I think the LCD would freeze with liquid nitrogen 🙂 The Canon dSLR’s are rated to function down to 0 C, below that you’re on your own.

Bill

(Bill Hilton) writes:

12 bits/channel (for Canon and Nikon dSLR’s)… see my other post.

From: westin* (Stephen H. Westin)

from a non-cooled digital camera. Chilled cameras routinely achieve 14 or 15 bits, and I’m sure the proper application of liquid nitrogen can improve on that.

LOL … I think the LCD would freeze with liquid nitrogen 🙂 The Canon dSLR’s are rated to function down to 0 C, below that you’re on your own.

I did say the *proper* application. Apparently astronomers do this all the time, cooling just the sensor chip and of course building the "camera" from scratch. Our cooled camera runs the chip at -25C, and has the chip in a vacuum chamber to prevent the formation of condensation and frost on the sensor. Noise is pretty low…

—
-Stephen H. Westin
Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors.

Bill Hilton wrote:

12 bits/channel (for Canon and Nikon dSLR’s)… see my other post.

From: westin* (Stephen H. Westin)

from a non-cooled digital camera. Chilled cameras routinely achieve 14 or 15 bits, and I’m sure the proper application of liquid nitrogen can improve on that.

LOL … I think the LCD would freeze with liquid nitrogen 🙂 The Canon dSLR’s are rated to function down to 0 C, below that you’re on your own.

That’s a bummer. What does one do in the snow? Both my film slrs function quite well below zero C. So does my Nikon 950.

—- Paul J. Gans

In article <c8e74j$3k2$>, Paul J Gans
wrote:

Chris Cox wrote:

Who said it was signed?

The range is 0 to 32768.

Chris

This is wrong no matter how it is interpreted.

No, it is correct.

16 bits can represent
65536 different values.

Yes, it can.

15 bits can represent 32768. If Photoshop
16-bit mode can only represent 32768 values then it is *not* a 16-bit mode.

No, it represents 32769 values. I said the range was 0 to 32768.

On the other hand, if source images such as those from various cameras (Canon, Nikon, etc.) claiming to be 16-bit images only contain 32768 different values, then they are not 16-bit images either, but 15-bit images.

So far none of them produce more than 14 bits/channel (until you get to some really expensive scientific cameras).

Chris

Chris Cox wrote:

In article <c8e74j$3k2$>, Paul J Gans
wrote:

Chris Cox wrote:

Who said it was signed?

The range is 0 to 32768.

Chris

This is wrong no matter how it is interpreted.

No, it is correct.

16 bits can represent
65536 different values.

Yes, it can.

15 bits can represent 32768. If Photoshop
16-bit mode can only represent 32768 values then it is *not* a 16-bit mode.

No, it represents 32769 values. I said the range was 0 to 32768.

Semantics. Sixteen bits can represent 65536 values and they are there even if Photoshop only uses the range you give. It is a strange range, but that’s esthetics.

On the other hand, if source images such as those from various cameras (Canon, Nikon, etc.) claiming to be 16-bit images only contain 32768 different values, then they are not 16-bit images either, but 15-bit images.

So far none of them produce more than 14 bits/channel (until you get to some really expensive scientific cameras).

I agree that fewer bits are significant, but the camera outputs 16 bits. We humans know that several of the least significant bits are useless and the software can implement that. But the hardware format contains many more values.

—- Paul J. Gans

Paul J Gans …

Chris Cox wrote:
…

So far none of them produce more than 14 bits/channel

^^^^^^

I agree that fewer bits are significant, but the camera outputs 16 bits. We humans know that several of the least significant bits are useless and the software can implement that. But the hardware format contains many more values.

"So far" being the key words. Sooner or later they’ll have to fix it. It will probably mean a leapfrog to 32 or 64 bit channels (&/or float/double/HDR).

Toby

—- Paul J. Gans