I have done a colour profile conversion from ProPhoto to sRGB test comparing different methods in PS, basically Perceptual against the others. I thought the Perceptual colour profile conversion, at the cost of altering some of the colours found in the boundaries of sRGB close to the border with ProPhoto, would reallocate some ProPhoto tones close to those boundaries into sRGB, so colour relationships are maintained in an attempt to keep some colour gradation in the ProPhoto areas out of reach for sRGB.
But nothing of that seemed to happen. I converted a softly graduated patch in the R and G channels (B=128 in all of it, I took one of the central patches in Bruce Lindbloom test chart: Bruce Lindbloom
-> Info -> An RGB Image Containing All Possible Colors), R varying from 0 to 255 in columns and G varying from 0 to 255 in rows, making use of all conversion models: Perceptual, Saturation, Rel Colorimetric and Abs Colorimetric, and all of them produced the same pixels going to 0 or 255 in the same channels
(R or G).
The conversion was done in 16 bit and converted to 8 bit for output. Anyway I also did the conversion in 16 bit and analysed the 16-bit output image, and the same pixels went black/saturated so it is not a matter of integer rounding.
This is the patch assigned
in ProPhoto and converted
These are the pixels where R and/or G channels went black (blue colour) or saturated (red colour) after the conversion:[span style=\'font-size:14pt;line-height:100%\']R[/span]
. [span style=\'font-size:14pt;line-height:100%\']G[/span]
And this is the intersection showing in gray colours those pixels that found a non-clippped correspondence in sRGB:
What am I missing? what is actually PS's Perceptual conversion doing