[argyllcms] Re: Conversion of spectral file to .cie
- From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 14 Oct 2016 08:52:09 -0700
On Oct 14, 2016, at 1:06 AM, Tomas Sobek <sankalpo@xxxxxxxxx> wrote:
My motivation is that there are supposedly slightly different variations of
the target and I thought if I use data that came with my one I will get
hopefully close to reality.
While there is measurable variation, it's well within the margin of error for
any graphic arts workflow. Indeed, you're all but guaranteed to have
significantly greater variation across the chart from uneven lighting and lens
imperfections. Much more significant is the fact that your lighting is
radically different from D50 (because D50 is an ideal which doesn't physically
exist), which itself requires special attention.
Creating good camera input profiles is difficult, and reflective charts are
extremely poorly suited to the task -- and 24-patch reflective charts are
basically useless for anything except photographing 24-patch reflective charts.
The only way to get not-miserable camera profiles is to use a workflow that
captures the camera's spectral response...and that's going to require either a
spectroscope or a monochromator, plus all sorts of other things.
(I should note that the ColorChecker Passport is a superlative standard
reference that plays an essential part in any color-critical workflow...but
that part is emphatically not in the creation of camera input profiles. Rather,
it's to normalize exposure and color channel balance, and possibly to fine-tune
scene illuminant characteristization.)
Without diving down a very deep rabbit hole, your best bet is to use Raw Photo
Processor with the profiles it ships with. Iliah Borg is making the best
general-purpose camera profiles of anybody these days. They're general-purpose
tools and come with all the limitations that implies; it's possible to craft
your own specific-purpose profiles that will outperform his...but doing so
requires a lot of equipment, knowledge, time, and effort -- and the payoff
isn't worth it unless you're doing something like fine art reproduction.
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