Relative Colorimetric with BPC and Perceptual

In many cases, you’ll choose Intent: Relative Colorimetric and check Use Black Point Compensation at Convert to Profile of Photoshop. Otherwise you’ll choose Intent: Perceptual. In many cases, they work well. In rare cases, they don’t. You should know about such cases until you choose them.

The phenomenon

Most dye-based black inks are noticeably untrue black. In other words, a* and / or b* isn’t close enough to zero. The untrueness is worse in sublimation inks. Yes, Zygomatic Color offers much better (but counterfeit) gray, but ICC profile cannot change ink property. Untrue black ink remains untrue.

But, the black ink makes the darkest color. So there is a choice:

• Darkest but untrue.
• True but not darkest.

Which is black? This is the problem.

Adobe ACE (and all other color management modules AFAIK) chooses the former. It grafts untrue black to true gray gradation. This is the situation:

The phenomenon is inevitable for most dye-based black inks. This is the case Use Black Point Compensation or Intent: Perceptual fails.

The deceiving practice in the industry

In ICC profile made by Zygomatic Color, and with Photoshop, you can see the phenomenon by Proof Colors. But most other ICC profiles don’t simulate the phenomenon. They ignore the fact, and play like ‘Black is black, black is always black, black is always true black, QED.’ This is what we hope, but not the fact. ICC profile can deceive the computer screen, but printed paper shows the fact. ICC profile should faithfully tell the fact from the screen.

How to avoid

Choose one:

• Darkest but untrue.
• True but not darkest.

If you choose the latter, edit your source image by Tone Curve until the darkest pixel is light enough to avoid the phenomenon.