Colour setup

Mike,
an enormous reponse but extremely useful. Thanks for taking the time to explain all of this, its clearly a complex topic but you have answered all of my queries.
I think I have narrowed the red cast to the printer and maybe this is why when I use the calibration the red seems exagerated however using the

corrections the final output seems OK. However, I will confirm this using the information below.

For information, I do use flat settings when scanning make all my corrections in PS and I scan using a greyscale wedge regularly.
Thanks again for such an informative response.

Regards,
Peter Detheridge

"Mike Russell" wrote in message

Peter Detheridge wrote:

I use an HP Scanjet 3C for most of my photo image work. I have just upgraded to PS7. I am confused as to how to colour management is meant to work.

Indeed you are not alone. Ever hear of the ancient Greek problem of circling the square, using only a straightedge and compass? Color management – meaning the use of custom profiles at every possible step

the imaging process, can be like that.

Though profiles can have substantial benefits, particularly in a multi workstation environment, setting up profiles for a smaller setup may

no

benefit because it can be as complex as the problem it is designed to solve..

Here’s why:
Documents created from the scanning process appear to have no profile embedded. I have multiple options eg use the default colour space (Adobe RGB) and no colour management. The images look ok on screen although they do not print true on my HP5550 Deskjet.

Do the prints have a color cast, and if so, at what point in the process does that happen? Is is after the scan, or after printing. To isolate this, print a grayscale step wedge visually check it for casts. If

are any, print it from another non-color managed app, such as explorer

netscape. It’s easy to make a step wedge, however until you have your

color

setup shaken down, I suggest you download the one from:
http://www.zocalo.net/~mgr/DigitalPhoto/digital_test_strip.h tm . This

step

wedge is also useful to check your display settings – it should be free

color casts when opened in Photoshop.

My scanner manufacturer make statements like the reflectance line of this scanner is set to enhance bright colours, greater saturation etc. If I want "true" colour to scan with specific highlight and shadow points.

Scanner manufacturers do tweak their colors – this is to be expected

they rightly consider themselves to be responsible for the "out of box" experience of their customers. Printer manufacturers do this as well. Epson, for example, has a PhotoEnhance mode that modifies the appearance

of

the printed image.

The maual also gives instructions how to calibrate the scannert using b&w and colour targets to the printer and or application(egPS).

This involves setting controls in the scanner software?

PS also offers the ability to Assign a Profile. One does exist for the HP Scanjet IIC (model below mine).

Fine, but if you use this be very careful to leave your other scanner settings "flat" – no other color correction or enhancements in the

software. Strictly speaking, you should not even set your black and

points, though in practice it turns out this is pretty much OK.

Here’ how I have it set up currently and producing "OK" results. I scan using the profile I generated using the printed targets through photoshop. The colours on the monitor are dreadful (red overdose and dark)

Before doing anything else, you need to address the red look to your

scans.

See if the grayscale wedge I mentioned above looks neutral on your

If it does, then your scanner profile is incorrect, and you need to keep trying until it gives you an image whose grays are gray.

I then assign the profile and colours normalise somewhat. I then use curves to do the ususal tonal correction etc and print. To my surprise this seems to give fairly accurate colour rendition. IE the printed image is true to the original and to my monitor.

Basically your color profile messed up your image, took your weeks pay, bonked you on the noggin, and dumped you down the river. You are now

having

to paddle back upstream, and when you get to town your profile will have spent your paycheck on cheap booze and cheaper women. Now I ask you, is your color profile is a good friend to go into to town next week with,

not?

Question is, am I trying to get too clever with this (I am only an amateur). Do I need to calibrate the scanner at all given the Colour Mgt capability of PS7?

Short answer – no, you do not need to calibrate your scanner. It may

you work to do so, or it may cause giant headaches. In any case you can scan and print your images with impunity provided the results appear

in

your judgement. If you do calibrate your scanner, then make sure the profile was created using flat scanner settings or you may get something worse than no profile at all..

In either event, do I need to assign the profile for the scanner to the image after its scanned and which option should I work with (eg none, Adobe RGB colour space)? Ie No profile, no calibration.

In general you would assign the profile to the scanned image. However,

you have already used the profile to modify the scanned colors, you decidedly do not want to do this. For example, if you have already

entered

the profile into the the operating system’s scanner color settings, or

scanner software itself, then assign the Adobe RGB profile to each newly scanned image.

Please note I have calibrated the monitor using Adobe Gamma and using the custom settings provide by ADI (ADI5G). The monitor has a gamma of 2.85

One warning here about a common pitfall. If you checked the box that

allows

you to adjust the R, G, and B gamma sliders separately, then it is

possible

that the reddish cast you mentioned before is due to gamma settings. I suggest you keep the three gamma sliders locked together as a single

slider

for the time being until you are sure about the rest of the process..

Perhaps all I am asking is what is the correct workflow for scanning images??

Whether or not you use profiles, the most important items on your color agenda should be:

1) correct white and black points
2) overall lightness and darkness of the image
3) getting rid of color casts

Any advice will be gratefully received.

Do look at Ian Lyon’s articles on color management and setup: http://www.computer-darkroom.com/

I would finish with the following: "Profiles schmofiles". At the end of

the

day, if you can scan an image and get neutral grays, with good black and white values, and correct overall brightness, how far off can you be?
Happy scanning!

—

Mike Russell
http://www.curvemeister.com
http://www.zocalo.net/~mgr
http://geigy.2y.net

Well I got that wrong. Using Mike’s advice I imported the wedge file with skin tones and printed directly to my printer. The image on the monitor showed no cast and neither did the printed output. Surprise! Using the output as a target I scanned it into Photoshop (with calibration set to "None" and no other scanning software adjustments) and the reddish caste became very apparent. Hence I now realise my scanner is the culprit. I then scanned again using the calibration I had set up in the HP Deskscan II software previously (having re-checked the settings etc) but this exeacerbated the red caste. Sticking with the uncalibrated scan, I applied the Scanjet IIc profile when opening the document and this seems to have removed most of the cast although the image was far from a perfect match to the original photo. However using Curves I resolved that fairly readily with the usal tonal corrections.
I guess I now have a choice. Either use the scanner software to modify the color setting during the scan (not very accurate) or continue on as described above, that is leave the scanner software settings flat and make all the adjustments in PS. I will experiment some more with the profiles to see if its better convert all documents to the Adobe RGB working space and then make adjuystsments or use the genercic scanner profile and make adjustments from there.
Regards,
Peter

"Peter Detheridge" wrote in message

Mike,
an enormous reponse but extremely useful. Thanks for taking the time to explain all of this, its clearly a complex topic but you have answered all of my queries.
I think I have narrowed the red cast to the printer and maybe this is why when I use the calibration the red seems exagerated however using the tonal corrections the final output seems OK. However, I will confirm this using the information below.

For information, I do use flat settings when scanning make all my corrections in PS and I scan using a greyscale wedge regularly.
Thanks again for such an informative response.

Regards,
Peter Detheridge

"Mike Russell" wrote in message

Peter Detheridge wrote:

I use an HP Scanjet 3C for most of my photo image work. I have just upgraded to PS7. I am confused as to how to colour management is meant to work.

Indeed you are not alone. Ever hear of the ancient Greek problem of circling the square, using only a straightedge and compass? Color management – meaning the use of custom profiles at every possible step in the imaging process, can be like that.

Though profiles can have substantial benefits, particularly in a multi workstation environment, setting up profiles for a smaller setup may have no benefit because it can be as complex as the problem it is designed to solve..

Here’s why:
Documents created from the scanning process appear to have no profile embedded. I have multiple options eg use the default colour space (Adobe RGB) and no colour management. The images look ok on screen although they do not print true on my HP5550 Deskjet.

Do the prints have a color cast, and if so, at what point in the process does that happen? Is is after the scan, or after printing. To isolate this, print a grayscale step wedge visually check it for casts. If there are any, print it from another non-color managed app, such as explorer or

netscape. It’s easy to make a step wedge, however until you have your color setup shaken down, I suggest you download the one from: http://www.zocalo.net/~mgr/DigitalPhoto/digital_test_strip.h tm . This step wedge is also useful to check your display settings – it should be free of color casts when opened in Photoshop.

My scanner manufacturer make statements like the reflectance line of this scanner is set to enhance bright colours, greater saturation etc. If I want "true" colour to scan with specific highlight and shadow points.

Scanner manufacturers do tweak their colors – this is to be expected since they rightly consider themselves to be responsible for the "out of box" experience of their customers. Printer manufacturers do this as well. Epson, for example, has a PhotoEnhance mode that modifies the appearance of the printed image.

The maual also gives instructions how to calibrate the scannert using b&w and colour targets to the printer and or
application(egPS).

This involves setting controls in the scanner software?

PS also offers the ability to Assign a Profile. One does exist for the HP Scanjet IIC (model below mine).

Fine, but if you use this be very careful to leave your other scanner settings "flat" – no other color correction or enhancements in the scanner software. Strictly speaking, you should not even set your black and white points, though in practice it turns out this is pretty much OK.

Here’ how I have it set up currently and producing "OK" results. I scan using the profile I generated using the printed targets through photoshop. The colours on the monitor are dreadful (red overdose and dark)

Before doing anything else, you need to address the red look to your scans. See if the grayscale wedge I mentioned above looks neutral on your screen. If it does, then your scanner profile is incorrect, and you need to keep trying until it gives you an image whose grays are gray.

I then assign the profile and colours normalise somewhat. I then use curves to do the ususal tonal correction etc and print. To my surprise this seems to give fairly accurate colour rendition. IE the printed image is true to the original and to my monitor.

Basically your color profile messed up your image, took your weeks pay, bonked you on the noggin, and dumped you down the river. You are now having to paddle back upstream, and when you get to town your profile will have spent your paycheck on cheap booze and cheaper women. Now I ask you, is your color profile is a good friend to go into to town next week with, or not?

Question is, am I trying to get too clever with this (I am only an amateur). Do I need to calibrate the scanner at all given the Colour Mgt capability of PS7?

Short answer – no, you do not need to calibrate your scanner. It may save you work to do so, or it may cause giant headaches. In any case you can scan and print your images with impunity provided the results appear good in your judgement. If you do calibrate your scanner, then make sure the profile was created using flat scanner settings or you may get something worse than no profile at all..

In either event, do I need to assign the profile for the scanner to the image after its scanned and which option should I work with (eg none, Adobe RGB colour space)? Ie No profile, no calibration.

In general you would assign the profile to the scanned image. However, if you have already used the profile to modify the scanned colors, you decidedly do not want to do this. For example, if you have already entered the profile into the the operating system’s scanner color settings, or the scanner software itself, then assign the Adobe RGB profile to each newly scanned image.

Please note I have calibrated the monitor using Adobe Gamma and using the custom settings provide by ADI (ADI5G). The monitor has a gamma of 2.85

One warning here about a common pitfall. If you checked the box that allows you to adjust the R, G, and B gamma sliders separately, then it is possible that the reddish cast you mentioned before is due to gamma settings. I suggest you keep the three gamma sliders locked together as a single slider for the time being until you are sure about the rest of the process..

Perhaps all I am asking is what is the correct workflow for scanning images??

Whether or not you use profiles, the most important items on your color agenda should be:

1) correct white and black points
2) overall lightness and darkness of the image
3) getting rid of color casts

Any advice will be gratefully received.

Do look at Ian Lyon’s articles on color management and setup: http://www.computer-darkroom.com/

I would finish with the following: "Profiles schmofiles". At the end of the day, if you can scan an image and get neutral grays, with good black and white values, and correct overall brightness, how far off can you be?

Happy scanning!

—

Mike Russell
http://www.curvemeister.com
http://www.zocalo.net/~mgr
http://geigy.2y.net

Peter Detheridge wrote:

Mike,
I may have confused you a bit. It was the profile I created using the calibration procedure described in the HP Deskscan II software manual that gave me poor results. It involes printing a target greyscale image and colour image, and scanning these. Just give it a name and its done. Just what it does I don’t have a clue; there is no file to save afterwards eg ICC and no settings or adjustments to make or change. Creating these was also a challenge as through PS I was confronted with the same questions ie no colour mgt, use Adobe RGB or assign the HP Scanjet II profile! I chose RGB for one and HP Scanjet for th e other both gave ugly results. Maybe I should try no colour mgt?

However, I’ve experimented more this afternoon. Scanning with no profile gave me underexposed (dark) photos. So rather than a setting of "none", I set the calibration option to one of the standard settings offered by the software, namely the default setting of Gamma
2.2 and got a much better exposure result (my monitor has a gamma
setting of 2.85). I then "Assigned" the Hp Scanjet IIc profile (in PS drop down list) and the cast dissappeared from my monitor and printed version.

I have checked the properties of the scanner itself and there are no settings for profiles. I had already removed colour mgt from the printer.

I wonder if improved scanner software might the go? Having said that, the results I got this afternoon are repeatable and the printed colours are close to the monitor so maybe I should be satisfied with that?

I’m suspicious of any procedure that involves printing out your own target and scanning it. My feeling is the accuracy of such a procedure is marginal, even if you were able to work the kinks out of it. You’re

off just relying on the accuracy of the scanner construction, and the

software settings.

The scanner profile I mentioned lives under the control panels. In any case, you now have a baseline from which you may judge any improvements

may get from profiles. So scan away by all means.

If you do want to improve the quality of your images, spend the dollars on any book by Dan Margulis, and train yourself to use curves well.
—

Mike Russell
http://www.curvemeister.com
http://www.zocalo.net/~mgr
http://geigy.2y.net

Mike thanks for your assistance. I am familiar with curves and have been working on furthering my understading of how to work with the end points and gamma slope using the "s" curve etc. I have found this exercise useful for this and for understanding the use of the individual channels.

As you say I now have a baseline to work to thanks to your pointers. I will now be more confident in proceeding with my photo retouching.