I have measurements for my different media using targets created by i1p AND targets created by pm5. Both sets have identical printer settings and slightly more than 2000 patches. So I can test i1p’s mapping when using its own targets versus when it has to use pm5 generated targets.
Thanks for your input on why to use relative versus why to use perceptual. I understand now and totally agree. After quite a bit of study and experimentation, I think relative colorimeteric is far superior for my purposes than perceptual. My printer spaces are close enough to my working spaces that the out of gamut color clipping issue I feared (versus perceptual scaling) is not really much of an issue. It’s extremely helpful to be able to see exactly what’s going on by using Colorthink. I’ve learned to use the worksheet.
I read Adobe’s paper on how their black point compensation works and that was helpful. Colorthink’s relative mappings don’t use black point compensation, so actually doing the conversions to printer space in Photoshop then viewing the mappings in Colorthink is useful. With bpc turned off, photoshop relative mappings are nearly identical to Colorthink’s mappings.
Almost all the original colors I’m capturing fit within AdobeRGB. I can test the questionable colors using my Eye One before I shoot, which is kind of fun, to see if they’re outside AdobeRGB. If so then I can use BetaRGB as my target working space rather than AdobeRGB, but this need is rare.
When I compare the media relative mappings of a 256 grayscale chart on five different papers in the worksheet, I see how the grayscale values get spread between the media black and media white points. When I look at those mappings, it makes me wish I had a “midpoint compensation” switch for the relative mappings so I could nail L50 to its absolute value and have the mappings adjust the tone curve above and below that as needed to accomplish an absolute midpoint.
I’ve tried to get a better understanding of absolute colorimetric mappings. I played with manipulating absolute mappings in printer space using photoshop–taking white to be paper white, creating my own black ramp, and seeing how the mapping of vibrant colors differed from a relative mapping both in photoshop and ColorThink. Not sure I really understand the nuances of absolute mappings yet. More study required.
I’m interested in gaining a better understanding of the media relative shifting of all colors when profile connection space white gets mapped to media white. I feel as if I’d like to have some control over the media relative color shift so I could keep more colors at their absolute mappings, yet still have a black compensation ramp, still have PCS white mapped to media white, have some volume of near neutrals get mapped to be neutral on the media, and have some volume of light tones, where media white has a distinct influence, get shifted relative to media white. Or maybe I’m totally crazy?
I haven’t tried anything other than the default “Profile White Point” setting in i1p yet. Seems interesting but not sure what it’s used for. Any experience with this setting?