[Digikam-users] Canon Color profile testing

Gilles Caulier caulier.gilles at kdemail.net
Fri Dec 8 10:57:46 GMT 2006

On Thursday 07 December 2006 19:59, Daniel Bauer wrote:
> Hello Gilles,
> first of all: thank you *very* much for the work you have undertaken with
> my sample!
> On Thursday 07 December 2006 14:22, Gilles Caulier wrote:
> > On Wednesday 06 December 2006 23:00, Daniel Bauer wrote:
> > > Hello everybody
> > >
> > > experimenting with colors... I have tested many different profiles, but
> > > I am still not happy with the results I get.
> > >
> > > As much as I can see there are two possibilities:
> > > 1) the Canon camera profiles we have are not really usable, or
> >
> > You need to use the right camera profile, fully compatible with the RAW
> > linear image resulting of dcraw conversion (16 bits color depth). More
> > info here abour RAW linear picture here :
> >
> > http://www.aim-dtp.net/aim/techniques
> >
> > To use the right Canon/Nikon camera ICC profiles fully compatible with
> > digiKam, i recommend hightly to use LightZone profiles. This program,
> > available for linux use internally dcraw 8.31. I'm sure, i have checked
> > the content of java tarball.
> >
> > I have extracted for you the icc color profiles :
> >
> > http://digikam3rdparty.free.fr/ICCPROFILES/CameraProfiles/LZ.2.0/
> Yes, I have already downloaded these from LightZone and found that the
> profile you used in the sample is the best till now.
> > > 2) I am just too stupid to achieve good results.
> >
> > no (:=),
> thanks :-)
> > but the ICC color profile is not the only piece of RAW workflow.
> > It more complicated. Let's me explain better with an example...
> >
> > > [...]
> > >
> > > But the most important first step: converting from Original CR2 to
> > > wide-gamut (or directly to SRGB) just doesn't give any good results
> > > with digiKam, no matter how I try. I think this is because we don't
> > > have really good profiles for Canon???
> >
> > no. because the profile is not the only one transformation to have the
> > right result. Look here :
> >
> > http://digikam3rdparty.free.fr/Screenshots/CR2RAWImport/CR2importInImageE
> >di tor.png
> >
> > .. in this screenshot, you can see on the middle the Color Management
> > plugin in action working on your CR2 picture to import RW file in editor.
> I guess for the photo in the middle you have already applied the later
> explained corrections, havn't you?


> > On the right showfoto have open your TIF WideGamut file generated by
> > Canaon soft. We will compare result with both windows.
> >
> > Note: of course in digiKam CM is enable and i'm decoding RAW files in 16
> > bits color depth.
> >
> > Now we back to the color management plugin. We need to adjust some
> > settings to complete import in editor, especially the right camera
> > profile from LightZone :
> >
> > http://digikam3rdparty.free.fr/Screenshots/CR2RAWImport/InputProfile.png
> >
> > ... the workspace color profile :
> >
> > http://digikam3rdparty.free.fr/Screenshots/CR2RAWImport/WorkspaceProfile.
> >pn g
> That's how far I came too till now...
> > ... and the lightness adjustement :
> >
> > http://digikam3rdparty.free.fr/Screenshots/CR2RAWImport/LightnessAdjust.p
> >ng
> >
> > This point is _very_ important : Canon, phtoshop, ufraw, lightzone used a
> > lot of Exif makernote provided by camera in picture to adjust automaticly
> > this settings. digiKam do nothing like this yet.
> Aha!
> > It's a piece of code to do
> > and it's planed to later (:=)))... This is want mean than _you_ must need
> > to do it by hand.
> Well, hmmm... In my personal view this is quite an important piece of
> code...

yes, but i need some time to understand how to do it. LightZone use an array 
of value reported to the console by dcraw to adjust automaticly the 
exposure/whitebalance after RAW decoding in 16 bits linear mode. UFRAW do the 
same + an indeep analys of makernotes using ExifTools. 

> because: how about doing this manually on 4-800 photos from an 
> average session? 

If time is a priority, Why not to use the Batch RawConverter kipi-plugin ? In 
the current implementation from svn it use the same engine than digiKam (i'm 
sure : i  have coded this part (:=))). Of course this plugins do not support 
16 bits color depth output but 8 bits color depth can be enough for you. The 
exposure/white balance will be automaticly adjusted by dcraw with 8 bits 
ouput (why not in 16 bits ??? ask to dcraw author for that...)

You can use JPEG/PNG/TIFF and set the right icc color space to use. Exif 
metadata will be preserved in JPEG/PNG but not yet TIFF because TIFF write 
mode is not yet supported by Exiv2 library. It under coding by Exiv2 author.

> Do I have to adjust this curve for each and every picture 
> or can I save a "succesful" curve and apply it to all the other photos,
> then?

The curve setting is restored between CM plugin session. You can use also a 
dedicaced settings file.

> I'll have to experiment with saved curves... (I fear such a curve 
> only applies to a single photo and has different effects on other pictures
> - thats how it is in photoshop - I'll see).


> There is also one principal thing about this Lightness Adjustments tool I'd
> like to say:
> The program continuously re-calculates preview, histogram and curves shape.
> This is nice, but on my PC (P4, 2.4GHz, 1G Memory) this is so slow that
> it's impossible to move the curve gently (it always "jumps behind" the
> mouse, know what I mean?). That makes it very difficult to make fine
> adjustments.
> Would it be possible (better?) to only re-calculate each time the mouse
> button is released, for example?

These optimizations are possible but are out of digiKam 0.9.0 goal. In my TODO 

> > After to set all adjustments, the import is complete :
> >
> > http://digikam3rdparty.free.fr/Screenshots/CR2RAWImport/CR2ImportDone.png
> >
> > Note : You can see a difference between Canon import and digiKam import
> > especially in highlight (look the wall light behind the chair). You can
> > see the problem in high value of histogram.
> I've chosen this sample picture because of difficult light situation
> (daylight from outside, neon light of different colours inside), high
> contrast and crazy colours.
> > Personally, thing than the digiKam import is better because the highlight
> > are not overexposed. I suspect a wrong setting in Canon soft perhaps the
> > gamma adjustment.
> most notably its more yellow, you're adjusting this later with white
> balance...

Yes, but look this comparison between Canaon RAW decoding tool and dcraw :


> > At this point there is 2 schools : set a full auto import, or a by hand
> > import. I prefer the second one, because when i shoot pictures in RAW, i
> > will work indeep all adjustements. If i want a full auto picture, JPEG is
> > perfect. This is why auto-adjustment like UFRAW is not yet done in
> > digiKam (:=)))...
> Well... Those two schools don't imperatively have to be mutually exclusive,
> why not let the user choose?

Yes, of course, but this is not yet coded (:=)))

> I shoot raw to have the most possible information. From my practical view I
> must differ between some single pictures where (in analog work) I stand in
> the darkroom and tinker a day or two until I have the perfect peace of art
> (my vintage prints are made like this), and the daily work, where "good
> enough" is good enough - in analog work I give them out to a
> machine-processing laboratory.
> With these "good enough"-pictures I expect the software to give me an
> average good quality. This is what the Canon software does. I then just do
> some small corrections (bring it back to the laboratory and say:), make it
> a bit brighter, give a bit more contrast, take away some magenta...
> > Ok, now we continue. Here we have the sRGB transform. On the middle the
> > digiKam image editor, on the right Showfoto with sRGB file generated by
> > photoshop :
> >
> > http://digikam3rdparty.free.fr/Screenshots/CR2RAWImport/ConvertTosRGB.png
> >
> > There is a difference between both image. This is is due to the first
> > stage of course, when we have imported the image from CR2 in wide gammut
> > color space. We can correct a little this point using Color correction
> > Image Editor tools like White Balance :
> >
> > http://digikam3rdparty.free.fr/Screenshots/CR2RAWImport/WBAdjust.png
> >
> > ... like this :
> >
> > http://digikam3rdparty.free.fr/Screenshots/CR2RAWImport/sRGBFinal.png
> Yes, but... the white balance of the picture is already fine from the take,
> you can see this in the embeded thumbnail. It is quite hard if I have to
> adjust all the pictures manually (still talking about the "good enough
> ones"), when I know it would be possible to have the good enough result
> automatically.
> I guess it works automatically in Canon software because it "uses a lot of
> Exif makernote provided by camera", if I understood correctly.
> Computer-technically I have no clue, but I guess the camera *must* provide
> all the necessary, or how else could it calculate a correct thumbnail to
> embed?

the thumbnail is an embedded JPEG file in sRGB color space. It have been 
converted using camera firmware. With the RAW file we need to reproduce the 
camera firmware. It not simple.

> What is the reason not to use this information in digiKam?

Because it's not yet coded...

> > It's not optimum, but the image is pleasant to read. The Photoshop sRGB
> > is too cold i think (it's my viewpoint of course (:=)))).
> I like it cold. Maybe because of my hot job :-)


> > To close my report, look the comparison between digiKam sRGB and
> > LightZone sRGB :
> >
> > http://digikam3rdparty.free.fr/Screenshots/CR2RAWImport/sRGBdigiKamvsLigh
> >tZ one.png
> >
> > ...It's the same. Normal, LightZone and digiKam use the same ICC camera
> > profile. The only difference is than LightZone adjust automaticly
> > Lightness correction and digiKam no.
> I havn't used LightZone, just downloaded it once to get the profiles... I'm
> a "digikamer" ;-)
> > Gilles
> I hope you take my mails not as a gripe. I am not complaining, I just throw
> in my views, because this is the only thing I can contribute to the
> development...

Sure, and i very appreciate.

> I want to have *hard* arguments for my friends and colleagues to move over
> to Linux.
> And very personally I really *want* a tool that makes my f***ing
> Win98-machine obsolete, I already get sick, when I have to boot it. In
> 8-bit mode I can do everything here on Linux very comfortable and fast with
> ufraw/digiKam, but 16-bit still lacks a bit in comfort when doing "good
> enough mass-production" under pressure of time, and that's what most
> photographers have to live with.

An auto-mode in 16 bits color depth with RAW file is the next stage to do in 

> So, thanks for taking your time and for lettting me take part a bit in this
> project. It's great what you do. But wishes never end...



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