OK, let’s carry on our adventures in the wonderful land of color management on Linux. We were talking about the monitor part of the CMS and we saw how to produce a ICC profile and load it in the video card. Today will be a lot easier with more screenshots: how to use it full steam in a color aware application.
We said earlier that Cinepaint is currently the best choice for serious photographic works. So we will see how to do color management with this software, also the same principles are available in The Gimp and others. Once you have an ICC profile for your screen and you have loaded it in the graphic card, you are ready to fire a color aware application and enjoy “true” colors – let’s say, “as close to the truth as possible” colors.
The first thing you want to do is tell Cinepaint which profiles to use and what to do with them. You do that in the preferences, as in the below screenshot, which is also a chance for you to see Cinepaint in all its (GTK2) glory:
You first go in the Folders tab and under color management, you make sure that the folder containing your monitor ICC profile is there. By the way, the consensus (as far as I know) is to put systemwide ICC profiles in /usr/share/color/icc and your own ICC profiles in ~/.color/icc. That is where Cinepaint looks for profiles by default.
Now if you move to the Color Management tab, you can now configure how Cinepaint will deal with ICC Profiles:
- You first tick Colormanage new display By Default to tell Cinepaint to go ahead and use CM.
- The Assumed Image Profile is the profile which Cinepaint will use by default with the images it opens. It should match the profile you chose in your camera – basically AdobeRGB (maybe sRGB).
- The Editing Profile is the profile which is used as standard profile for the image color transformations. AdobeRGB is a safe choice once again (although other choices with wider gamut exists, such as Wide Gamut RGB).
- The Display Profile really is the monitor profile. So chose the ICC profile for your screen – watch out, even if my profile is called something like Samsung_27_12.icc, it always appears as ColorPlus since Cinepaint uses the author tag to display the profile name and not the profile file name. It is a bit uncomfortable if you have several monitor profiles: they will all appear as “ColorPlus” so you have to figure in which order they appear from the alphabetical order of the filename. Not ideal.
- The Proof Profile is used for printing simulation, we will get there later.
- The Default Rendering Intent tells Cinepaint which policy (yes you should know what that means by now) to use when translating colors from one profile to another. Perceptual is the logical choice there – even if it says relative on the screen shot.
- I don’t have a clue what Default Transform Calculation does, so I leave it on CMM default
- Black Point compensation tells Cinepaint whether it should remap the darkest point of one profile to the darkest point of another. Whether this is a good idea or not is debated, but as far as I understand, it is more important for press or offset printing (where gamuts are really small) rather than screen or inkjet printing (what we deal with it here). So mine is ticked
- The Behaviour bit deals with what Cinepaint should do when a new image is opened: for me it assigns the assumed image profile. The logic behind that is that my camera is set to produce AdobeRGB files and that Cinepaint should assign (ie consider the image as being produced in) AdobeRGB. So that looks logical.
- In case of mismatch between the assumed profile and the profile that the image reports (say the image is sRGB and my assumed image profile is AdobeRGB) it prompts me about what I want to do. Basically that means that when you open an image where profiles mismatch, you get a pop-up asking you if you want to convert the image to the new profile or change the editing profile (from AdobeRGB to sRGB in this case). This should normally rarely happen, so not much to worry about – we will talk about converting images from one profile to another later, on the subject of printing.
All that stuff really looks complicated and (very) verbose. However, once you have sane defaults and a stable workflow, CM is transparent. You work on your images as usual but the CMS is doing its job: you know you see the “true” colors on your screen, you know your prints will look very close to what you have on your screen. So don’t get discouraged. It is tough to get a proper setup and understand the principles / concepts, but once the initial setup is done, you don’t touch it anymore and the reward is well worth it.
A nice little one from Ardeche, to get us going
February 22, 2008 at 7:31 pm |
Joel, I was wondering why you are not using your camera-specific input profile .icm instead of the Adobe RGB?
Also, a bit off-topic, as a fellow Pentaxian — are you following the discussions on pentaxforums.com?
February 23, 2008 at 12:09 pm |
Hi there,
The camera is set up to produce either AdobeRGB or sRGB files, so there is some color transformations already going on inside the camera. And the goal of the editing profile is to be a standard across cameras, scanners, etc.
The use case scenario of a camera profile is if you work from a RAW file to which you apply your camera profile and which you then save (after dematricing) as a TIFF file in AdobeRGB. But I am not even sure how much gain there is there – if someone knows better?
I do read pentaxforums but I don’t write there
Take care, fellow Pentaxian…
Joel
February 28, 2008 at 2:31 pm |
Joel,
first of all, congratulations on your blog. It is an incredibly useful (and growing!) reference for linux and photography. I used argyllcms to calibrate my screen on the basis of your posts on the topic.
I downloaded Firefox 3 and installed Gimp 2.4 to test color management from end to end – so you could say that I am a big fan of this “Helpful stuff” – from my point of view the “I hope” can be deleted now.
I have a question however on Gimp 2.4 and color management (maybe Cinepaint is similar). When the screen is calibrated (with dispwin) and I set Gimp to use the icc profile of the screen to display the images, the colors are too intense. Since the images are sRGB, I can compare with Firefox and gqview, and there is a difference. When I set the display profile to “none” in Gimp, the image shows with the “correct” colors in Gimp. Am I doing anything wrong?
Merci d’avance!
February 28, 2008 at 5:24 pm |
Hello Seb,
Thanks for the compliment
You are raising an interesting issue: how do I know what to trust when renditions are different?
My advice would be to use Cinepaint as a base (see here for details about enabling CM in Cinepaint) since it has had CM support for quite a while. Compare the result with Gimp and Firefox (with the monitor profile loaded). I don’t think gqview is CM aware…
Depending on the picture / colors, the difference when you tick Enable CM can be minimal or very important – especially if you boosted the colors in a non CM environment and then move to CM. So it can be that your “correct” colors are in fact over-saturated due to processing them in a non CM aware environment
I hope this makes sense.
Take care,
Joel
August 22, 2008 at 6:29 am |
Hello Joel,
GQview 2.1.5 is color aware — there’s a small icon in the bottom-right corner where you can enable color management and switch between different profiles (e.g. if you have multiple monitor setup). You can manage profiles on the “Advanced” tab in preferences.
In my personal opinion, GQview rocks!
Dariusz
March 23, 2009 at 12:16 am |
[...] get an icc profile which you can load with dispwin or xcalib (for screen calibration) as well as your graphic application (for profiling – if the application supports it). Check this entry if you need to know more about [...]