[argyllcms] Re: perceptual black too light

Graeme Gill wrote: 
The explanation as to why the output doesn't necessarily match the
destination black point, is that with the new gamut mapping, I'm not
assuming black point adaptation, so the src black point doesn't
map to the destination black point. The source black point will
be adapted to any src->dst shift in the white points,

Graeme,

may I ask, how do you actually align the two white points (and how do you adapt all other source colors according to the WP shift)? Just a translation in Jab space? Chromatic adaptation? Rotation from src WP to dst WP in Jab space with center at [0,0,0]? Etc.?
and will be adapted in J to have the same J as the destination black point,
but target grey axis direction is not affected by this. As a result,
the desired output value corresponding to the input black point
may get clipped to the output gamut, raising the J value,
and moving the a & b towards the darkest point in the destination gamut.
So if I understand you correctly, the direction of the perceptual gray axis of the device being profiled is eventually determined by the wtpt..bkpt axis of the supplied _source_ profile (-> profile ... -S ...), while the lightness of the lower end of the device's gray axis is determined by the device's bkpt? What's actually the intention of this strategy? Looks like the created device profile inherits some of the source profile's personality (gray axis direction), but is this really desired in general? Shouldn't the device profile being created for a particular device rather represent the "native personality" of the device?

Regards,
Gerhard


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