Vallo Kallaste wrote:
Can anybody please tell me why using the Lab cLUT display profile cause lost dark shadow detail? The data set for profile generation is same and shaper+matrix profile (colprof -as) has no such effect in Photoshop CS2.
The usual reason is the lack of appropriate gamut mapping. If you connect a source profile with a zero black (ie. such an idealized sRGB or AdobeRGB type profile) to a profile that has a non-zero black point (ie. like a real world diplay profile) without gamut mapping, the blacks get clipped. [For colorimetric they always get clipped, because that's what you've asked for in selecting Colorimeric.] In theory Adobe BPC should fix this, but (for some unknown reason) it's not available for all intents, and BPC isn't available for all applications. There is another way using Argyll:
colprof -v -qh -D"3008WFP-2.2-Lab" 3008WFP-2.2
Figure out what your source colorspace is, and feed it into colprof as the source colorspace, so that it can be used for creating the gamut mapping in the Perceptual and Saturation B2A tables. For instance, say your source image is in sRGB space: colprof -v -qh -S sRGB.icm -D"3008WFP-2.2-Lab" 3008WFP-2.2 [Use the sRGB profile in the Argyll distribution if you want to avoid problems caused by "sRGB" profiles that don't follow the sRGB spec.] Make sure your image is in sRGB space (ie. that's what's embedded in it, or selected as the RGB colorspace), and that you're selecting perceptual intent when you use the display profile, so that the gamut mapping gets used.
know what to expect. Should also note that using the same Lab cLUT profile in Picture Window Pro I'm currently trying out gives better details in the deep shadows. PWP is set to using lcms. It's really frustrating because no
Maybe BPC is turned on for lcms. Graeme Gill.