[argyllcms] Re: Dispcal - Inverting Jacobian failed?

Graeme Gill wrote:
> The thought that crossed my mind was that it might be useful
> to have an option to measure a number of points and plot the
> resulting curve. Perhaps there could be a couple of selections
> (ie. 8, 24, 64 measurements) so that the user can choose how
> long they want to wait.

Hello Graeme, another though coming into my mind is do display an image
with RGB patches

    [254,255,255] [255,254,255] [255,255,254]
    [253,255,255] [255,253,255] [255,255,253]
    [252,255,255] [255,252,255] [255,255,252]
    [251,255,255] [255,251,255] [255,255,251]
    etc.

on a white background. As long as no clipping occurs, the color of each
patch should differ from the white background surrounding the patch.
This would avoid the need to perform measurements; the test image can be
displayed statically and judged visually. The problem is however, I can
indeed measure a difference between e.g. RGB [254,255,255] and
[255,255,255], but my eyes cannot distinguish this difference - so the
visual assessment will be less accurate and may lead to falsely assuming
the presence of clipping (I must admit though, that the measured
difference in this example does not have a perfect statistical
significance either unless I average a couple of readings of each RGB
color). Also possible is of course a combination, i.e. to use a wedge
with coarser, visually clearly distinguishable RGB steps (with a step
size of say 5 RGB units) for the coarse adjustment, but still do
measurements for the final assessment.

Regards,
Gerhard

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