Hello,
Thank you for your answers.
On 2017-03-03 15:58, Chris Siebenmann wrote:
I recently purchased a Canon EOS 80D, I am a Debian (8.7) user. All
this
is quite new to me so it might be a newbie question rather than a
problem with Darktable. Sorry beforehand if that is the case.
TL;DR: http://imgur.com/a/eEipd
When importing photos (CR2) into Darktable (2.0.7),
colors/contrast/brightness... aren't the same as in the "Gnome
Document
Viewer" preview (and on the screen of my 80D).
What I suspect is happening here is that the version of the image that
the Gnome Document Viewer preview and the 80D are showing you comes
from
a 'preview' JPEG that is embedded into the RAW file (most RAW files
have
several preview JPEGs in them at various sizes). This preview JPEG has
had all of the camera-specific magic processing applied to it,
including
any in-camera styles you either set yourself or that Canon applies by
default.
The darktable picture seems to be from the darkroom, where darktable
is processing the RAW itself from scratch. This from-scratch processing
almost never exactly duplicates the camera's own processing (partly
because camera makers never tell anyone what the in-camera stuff is
actually doing), and is sometimes not at all similar to it depending on
what settings the camera and darktable have. Generally the further from
'basic neutral' you have the camera on, the more divergence there is
going to be.
(Note that most cameras don't come set to 'basic neutral' out of the
box; usually their default picture setting is more cranked up than
that,
because it looks nicer on the back of the screen and when people just
use
the JPEG defaults.)
This is an issue in any RAW processor (apart from the ones from the
camera companies themselves), because none of them know exactly what
the in-camera processing is doing. Some RAW processors devote more
engineering and development effort to closely matching the straight
out-of-camera processing than others do, and so will come closer to the
look of those JPEGs by default. My impression is that darktable chooses
to focus development efforts elsewhere, so it winds up not necessarily
very close for many cameras and many camera styles.
(There are ways to get it closer in some areas if you want to do
some hand work. There are darktable tools that take some RAWs and
some corresponding JPEGs and work out much of the intensity/contrast
mapping between them to create a custom 'base curve' for the camera and
style. However cameras also often add things like colour shifts and
various sorts of sharpening and so on, and those are generally not
going
to be duplicated through the base curve's mapping of intensities.)
That is insightful, thank you. Using the "base curve" tool, and
selecting the "eos like profile really helps.
Playing around withe the various modules in the darkroom, I managed to
get close to the "preview jpg" render (I find it close to what I shot -
through the viewfinder, in manual mode - particularly, regarding
colors).
1: CR2 as seen by the Document viewer ;
2: Darktable default ;
3: Darktable edited (base curve, contrast, shadows, demosaic, sharpen).
https://imgur.com/a/0M3ez
I am still having a hard time reproducing the same (~ red) color for the
trackpoint (look at #1 and #3 side by side, #1 is the real color). Any
clue on what module to use to fix that ?
On 2017-03-03 16:29, Roman Lebedev wrote:
Also see
https://www.darktable.org/2016/05/colour-manipulation-with-the-colour-checker-lut-module/
Thank you.
I got to say that I laughed out loud reading this article. I hold a
masters degree in engineering and reading through it felt like reading
Klingon.
There are so many undefined acronyms (ICC and LUT aren't defined for
instance (I actually had to wait until the 6th iteration of LUT to get a
confirmation that the author was actually talking about lookup tables))
or, when it comes to formulas, undefined parameters (like "CIE 76 ΔE")).
This being said, and after googling every undefined term, the article is
also insightful but is still too cryptic for me to be able to reproduce
the process to generate a proper custom style (base curves, color
matching, etc.). I am wiling to do so (buy the it8 target etc) and share
the result with the community but I am going to need help.
On 2017-03-03 15:59, Guillermo Rozas wrote:
what you're looking at is the difference between the in-camera Canon
processing and Darktable's processing. DT has its own way of
processing the RAW data in the CR2 file that is not 100% the same way
Canon uses, which produces changes in the final output. Is not that
one or the other are right or wrong, they're just different.
When importing photos (CR2) into Darktable (2.0.7),
colors/contrast/brightness... aren't the same as in the "Gnome
Document
Viewer" preview (and on the screen of my 80D).
The Gnome's viewer is probably using the JPG preview embedded in the
CR2 file, and in that case it should look almost the same to the 80D's
screen. DT takes the real CR2 data and processes it, so it will almost
always look different (it's also color managed, so there may also be a
difference there if you profiled your monitor)
I initially had problems with Darktable 1.4.2 where every photo (same
format, same DSLR) imported would look pink. I upgraded to 2.0.7 and
the
problem was gone, that is why I suspect that this might be another
darktable-related problem.
Your problem with DT 1.4.2 was probably related to the camera being
unsupported yet (wild guess). What you have now is probably not a
problem, just a different look. I had the same "shock" the first time
I used it, because one is used to the Canon processed look and DT's
look "different". But after a while I learned to stop looking to
Canon's JPG as "the" target and perfect processing, and to use my own
judgement (and DT powerful processing) to decide how the image should
look like.
So, don't worry! Start playing with DT (and read the manual), and
you'll soon find out that you can control the final image much more.
Thank you.
That's what I did after reading through the all the insightful answers
that I received. Now I am really looking forward to create a dedicated
style for the canon eos 80d and to release it.
CA
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