The real use, I find, for measuring a CC24 is for screen and print
profiles, to check them visually one needs an image file with the measured
chart values rather than generic.
This applies to the bunch of us on list of course, probably not to the
general population ...
In past experiments I found by writing my own profiler in Matlab that CC24
is useful for deriving accurate primaries in situ in mixed light; I
wouldn't use it for a generic profile myself.
I do wish camera makers provided a file tag with spectral sensitivity
On Friday, October 14, 2016, Elle Stone <ellestone@xxxxxxxxxxxxxxxxxxxx>
On 10/14/2016 11:52 AM, Ben Goren wrote:
On Oct 14, 2016, at 1:06 AM, Tomas Sobek <sankalpo@xxxxxxxxx> wrote:Hi Ben,
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
(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
I have learned a lot from reading your posts to this list and I'm always
interested to read what you write - thanks much! for sharing over the years.
Deriving custom chart readings for the ColorChecker might not be not worth
doing for all the reasons you give. Also 24 patches is not a lot of patches
when making even a general purpose camera input profile, though this forum
has seen long debates over the adequacy of ColorChecker's 24 patches vs
other targets with more but perhaps lower quality patches.
But I would like to ask - as your own knowledge deepens and as you
experiment with ways to make accurate profiles for your very controlled
studio lighting using your increasingly interesting (and complicated!)
laboratory setup - is it possible that you might be raising the bar too
high for the rest of us mere mortals who just want to make a general
purpose camera input profile that might be more useful and even perhaps a
bit more accurate than whatever input profile is supplied by whatever raw
processor we might be using?
Unless they make their own camera input profile, Linux users and people
using free/libre raw processors perforce use the camera matrices in dcraw.
I think ACR/Lightroom and a bunch of other proprietary raw processors also
use these matrices. Are you saying that there is absolutely no point in
trying to make a better general purpose input profile than the matrices in
dcraw? AFAIK, many (maybe even all?) of these matrices were made by
shooting a ColorChecker target.
I'm sure Iliah makes wonderful general purpose camera input profiles, and
if he wanted to make his profiles available for people who don't run Mac,
that might be a very nice thing. But right now advising people to use RPP
profiles seems equivalent to advising them to go buy a MacIntosh, as RPP
doesn't seem to be available for Linux or Windows.