CS4/Leopard fix for printing targets, Thank you Mark and Eric. Options

[digitaldog]

... in order to print images via Photoshop you would have to convert or assign the printer profile to the document profile to keep colorsync from interfering.

You have to convert, assign will not work (it doesn’t change the numbers, only the definition of the numbers).

If you convert the profile whites are no longer pure IE RGB 255.

Did you pick an Absolute Colorimetric intent?

[madmanchan]

There seems to be some miscommunication regarding the scope of the proposed workaround.

The proposed workaround was only ever intended to be used for printing profile targets, for the purposes of building profiles.

It was never intended to be used for printing normal images, once you already have profiles.

It is possible that other, related workarounds are needed to print normal images if using an older printer model with an older driver. It would not surprise me. However, I have not researched it.

[adamlogan]

@ digitaldog

I used the perceptual rendering intent when converting document profile to match the custom printer profile. I picked perceptual rendering intent in the print dialogue as well but I am guessing that this is moot since there is no out of gamut colors after the conversion has taken place.

I still gotta wrap my mind around some concepts in color management. Right now I'm struggling to visualize what exactly assigning a profile to the document color space does. The same RGB number would look different depending on the color spaces because some are bigger, others are smaller, and they encompass different spatial dimensions. Pro Photo has yellows that Adobe RGB does not. When I assign the custom printer profile, is that kind of like "Preserve RGB Numbers"? Sorry for bringing this up here, I guess I'm getting off topic. I am just eager for a resolution, but it's also important to me that I understand what's going on with my colors.

@ madmanchan

Are you talking about the Generic RGB workaround? What are some other workarounds I should investigate?

[eronald]

There seems to be some miscommunication regarding the scope of the proposed workaround.

The proposed workaround was only ever intended to be used for printing profile targets, for the purposes of building profiles.

It was never intended to be used for printing normal images, once you already have profiles.

It is possible that other, related workarounds are needed to print normal images if using an older printer model with an older driver. It would not surprise me. However, I have not researched it.

If you can print a target, you can can also print with the resulting profile: Do a conversion using relative or perceptual intent of any image into devicespace, and then print it using your devicespace workflow. Converting using absolute won't work with normal profiles, unless I'm wrong, because of a white point issue, although I've heard this can be easily fixed by editing the profile. Whether you actually need such a workaround for printing images is a different story; however the above technique is one I use regularly for assembling composite images when testing gamut mappings or comparing profiles.

Edmund

[digitaldog]

I still gotta wrap my mind around some concepts in color management. Right now I'm struggling to visualize what exactly assigning a profile to the document color space does. The same RGB number would look different depending on the color spaces because some are bigger, others are smaller, and they encompass different spatial dimensions.

R0/G255/B/0 isn’t the same color in sRGB as Adobe RGB (1998) nor ProPhoto RGB. Same number, different color (because its a different color space). When you assign a profile, you tell Photoshop the scale of the numbers. The number don’t change, the color appearance does because the definition of the numbers, the scale is different.

[abiggs]

well articulated, Andrew.

[adamlogan]

@ digitaldog
Thanks for the explanation, very clear. I find it strange that 255 permutation of each color (RGB) has different "scale" in different color spaces.

@ eronald

Converting using absolute won't work with normal profiles, unless I'm wrong, because of a white point issue, although I've heard this can be easily fixed by editing the profile

How would I go about doing this? Make a copy of the RGB 1728 Bill Atkinson reference file and change the RGB number for the first patch? Does it involve editing the image itself in Photoshop?

[digitaldog]

@ digitaldog
Thanks for the explanation, very clear. I find it strange that 255 permutation of each color (RGB) has different "scale" in different color spaces.

Think of it this way. If you ask me how far I live from you and I say 1000, you don’t know if I mean 1000 miles, 1000 yards, 1000 kilometers. When we say G255, without the scale (the color space), the number alone is as ambiguous as when I say “I live 1000 from you”.

When Photoshop knows G255 is associated with a scale (sRGB, Adobe RGB (1998), ProPhoto RGB), it can now preview the color based on that info. So the preview updates. The numbers don’t.

Gas in the US and gas in the UK are basically the same. But when I ask someone the cost of gas and they are buying it by the litter and I’m buying it by the gallon, while the gas is the same, the resulting number isn’t because the scale is different.

If you look at the CIE chromaticity diagram which defines human vision, if you plot the gamut of sRGB and then ProPhoto RGB, you see 255G falls in a vastly different location (the scale is not the same). We use the same numbers to define the most saturated green but they fall in different locations within color space. Numbers alone can’t define a color. We need numbers and the scale, in this case, the scale is a color space.

[DesW]

But when I ask someone the cost of gas and they are buying it by the litter and I’m buying it by the gallon.

G'day Dog,

Ummm-- You mean from a CAT(cracker)or for a CAT(alytic) vehicle?


DesW