On 21 Sep 2015, at 04:11h, Ben Goren <ben@xxxxxxxxxxxxxxxx> wrote:
On Sep 20, 2015, at 5:15 PM, Hening Bettermann <hein@xxxxxxxxxxxxx> wrote:
I have earlier used -am, but -aX gives better Delta-E values.
A close fit for a small number of samples generally doesn't mean all that
much. Indeed...unless you've got a *lot* of samples and an impeccable
workflow for generating them, you're almost always better off with a looser
fit. Especially over the part of the gamut that you can sample with
reflective charts, cameras are remarkably linear and well-behaved. Unless you
really know what you're doing anything other than -am -qm is going to give
worse results, because you're making the profile tightly fit the errors in
-ax -qh has its place...but I don't think I'd recommend it for anything
smaller than a few hundred spectrally diverse patches. I use it...for
synthetically-generated charts of tens of thousands of patches completely
covering the entire theoretically-possible set of reflective spectra. That's
where -ax -qh really shines.
But if you're making a profile from a commercially-available reflective
chart, -as -qm is your best bet.
Especially over the part of the gamut that you can sample with reflective
charts, cameras are remarkably linear and well-behaved.
Is there a reason to think Hening's camera is saving significantly nonlinear
results in the raw file?
Some raw processors (digiKam's raw processor) do apply a tone curve over which
the user has no control, in which case "-aS -qm" or "-aG" would seem to be a