It has to do with rendering intent. This is the way in which out of gamut colours are converted when going from a larger to a small colour space.

I will have an artcile on this subject online in a few weeks.

Michael

No. It is also possible you have some color settings set wrong in your print driver or print application (Photoshop, QImage, or RIP) and the colors are not being converted correctly. If that is the case, the color space that most closely matches your printer's native color space will give the best results, but none of them will be quite right. If you're printing an image with no out-of-gamut colors, neither the rendering intent nor the document color space should matter; prints should be identical. Try desaturating a 16-bit image by about 50% (so there are no out-of-gamut colors), convert it to various color spaces, and print. If they aren't identical, you know you have some color settings wrong somewhere. Also, try using relative colorimetric rendering intent (with black point compensation) instead of perceptual.

That's what printer profiles do. Custom profiles do this more accurately than generic ones. But there really is no reason to obsess about which editing space matches your printer space, because if this is even an issue you have misconfigured color settings, and nothing is really going to work properly until you fix that.

A printer profile is a mathematical description of the printer's native color space for a given driver setting, paper type, and inkset. But it is not the color space itself.

can anyoen explain to me why when I print the same picture that has been processed in prophoto mode and then converted to argb before printing i get a "truer" print than if I don't do a conversion? I am printing on a r2400 with epson profiles.

thank you....does it mean I should always reconvert to argb before printing?

how does one determine the the printer's native color space?

ok i understand that. i just didn't know that a printer profile was refered to as a printer's native color space. thank you for the info, much appreciated

This question is not strictly about ProPhoto, but it's relevant.

I'm just getting the hang of the basics of colour workflow. I have a Minolta MultiPro film scanner, which I scan Velvia trannies with, in 16 bit. The Minolta software can convert into  AdobeRGB colour space.

I bring this into Photoshop CS, with working space set to Adobe RGB.

My monitor is a Hitachi glass screen, calibrated with a Spyder.

Now, I understand that the monitor's gamut probably doesn't cover much more than sRGB, so what does Photoshop do to display the image on the screen? Does it do a relative colorimetric conversion, thus clipping out-of-gamut colors, or does it do a perceptual one, thus compressing and desaturating everything? I'm guessing at the moment that it clips?

In which case, how do you tell how much has been clipped on the screen?

And, if this is the case, won't it be even more difficult to work with the out of (screen) gamut colors that exist in an even wider gamut source image? i.e, it's fine for both the image and the printer to have wide gamuts, but the screen is going to let the process down a bit?

Also, what's a good way to see how big a gamut your monitor is capable of? Is there a test image somewhere, say tagged in ProPhoto or RGB, which has the sRGB sub-range shown on it? How could I use such an image in PhotoPro to see how my monitor performs compared to sRGB space?

Thanks,
Milt