Re: [APML] Color space settings in PS

[Jerry Lodriguss <jerry@astropix.com>]

At 04:23 PM 8/10/2003 -0700, you wrote:
>Jerry, what I mean by that is for normal processing of astro images, I went
>from srgb to Adobe RGB.  When I make prints with my lame canon printer, I
>have to use a different monitor profile to match the output.  to do this, I
>open my video card settings, and adjust the color on the screen to match the
>print.  Then i SAVE it under a new name - canon printer.  But when I go back
>to normal stuff, like image processing, I revert back to no settings.  Sound
>reasonable?

Hi Chris,

If you start out with an image in sRGB, there is no reason to go to Adobe 
because sRGB is a smaller space to start with. The colors are limited in 
sRGB. Going to a larger space (Adobe) doesn't give you more colors. You 
have already lost them in the beginning when you first started in sRGB.

An analogy would be... you have one quart of "colors" in an sRGB can, and 
you pour that sRGB one quart into a one gallon "Adobe" can.  You still have 
the same colors, only in a larger space, but you do not get any more colors.

Likewise, in the other direction, if you do have real colors in a larger 
original space (Adobe), and you pour them into a smaller space (sRGB), you 
have to throw some colors away to make them fit. (usually the most 
saturated colors get thrown away in this example).

Note that this is in a theoretically perfect world. In the real world, you 
might not even notice any missing colors in sRGB. It just depends on the 
subject matter. If you original was of some incredibly colorful subject 
shot on Velvia, then you would notice a loss of some of the most saturated 
colors in sRGB.

If you are using a recent version of Photoshop that supports color 
management, you should obtain a profile for your printer, and then just 
soft proof it or convert a copy to the printer's color space. That's the 
easiest and most accurate way to do it (presuming, of course, that you have 
an accurate color profile for your printer).

The way you are doing it is similar to the way you had to do it before 
Adobe implemented color management in Photoshop.  It can work, but it's 
easier to use profiles.

I don't know what Canon printer you have, I have a 4300, which is about 5 
years old, and mine came with some canned generic profiles for it. There is 
a different profile for just about every different kind of paper you could 
use.  If you have them, they would be visible in the Image > Mode > Convert 
to Profile dialog.

Jerry


Photoshop for Astrophotographers - http://www.astropix.com/PFA/PFA.HTM











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