Black point compensation

The Print Preview dialog in Photoshop is not color managed, so what you see there is not really accurate in terms of CM.

However, are you saying that printing the same file from Aperture and Photoshop using the same destination ICC profiles with BPC enabled is giving you very different results on the same printer?

I have also had similar results when printing from Aperture. To be honest, I don't know if it's a bug, or just a difference in the two tools (CS2 vs. Aperture).

What I can say, however, is that lately when I'm printing from Aperture, I turn "off" Black Point Compensation, set the gamma to 1.15, and I have the the closest match between LCD/prints that I've ever had. I am VERY pleased w/this combination. I'm printing to the Epson P2200. The colors, overall brightness, etc are a perfect match. When I used BPC "on" and other gamma values, the overall colors and tone were not very good.

regards
Tom

I just found this link which explains pretty well why changing colour space using BPC can sometimes actually lighten the image. If you create a B&W image with really black areas in it you should be able to see this clearly if you toggle BPC on and off:
http://www.newsandtech.com/issues/2004/05-04/pt/05-04_blackpoint.htm

Regarding the differences in ColorSync CMM and ACE, that could play a part. Have you tried using ColorSync in Photoshop to see if the result between Aperture and Photoshop are identical? I'd be really interested to know... especially as I was thinking of maybe getting an SP2200.

I am right in concluding from the linked article that you should in principle use BPC (assuming you want to preserve all shadow detail) when converting but not when viewing or printing a proof?

(And shouldn't any software that has a proofing option do this automatically right?)

Hi Markus,

Not quite - what the article shows is that BPC is generally a good choice if you are moving from a color space or range of colors in your image (Adobe RGB, for example) that are greater than those in the destination space (nearly any print device) because it keeps the tonal range of the shadows in the image correctly related to each other by mapping the blackest black in your image to the blackest black possible on your output device then shifts the other blacks relatively. As John Nate says:

"the maximum black in Adobe RGB will be remapped to the slightly less dense black of the inkjet printer and all of the other tones will scale accordingly"

However, if you then have a situation where you have an image that has a very restricted black tonal range - an image that has already been prepared for newsprint, for example - and convert it to another space - Adobe RGB, for example - then instead of mapping the image accurately as it would appear in newsprint, BPC over-compensates and shifts the washed-out blacks of the 'correct' newsprint image to the deep blacks possible in Adobe RGB. So, if you are trying to get an accurate on-screen or inkjet proof from the newsprint-ready image, BPC will mess things up.

In short, most of the time when you are moving from sRGB or Adobe RGB etc. to inkjet or print, you can fairly safely leave it on. When you are dealing with images already converted to CMYK, and you want to maintain their appearance as it will be seen on print, it is best to leave it off.

Powerbook, Mac Mini (Intel) Mac OS X (10.4.8)

Powerbook, Mac Mini (Intel) Mac OS X (10.4.8)