Articles and tutorials on ICC profile color management and free/libre image editing
The philosophy behind the Nine Degrees Below color management articles and tutorials
Many times, articles on color management assume that all the reader really wants to know is which buttons to push. On this website the first assumption is that you want to understand enough about color management to make your own intelligent decisions.
The second assumption on this website is that you run Linux and use free/libre software. Most articles on the internet that discuss color management assume that you run a proprietary OS and use PhotoShop.
Fortunately the principles of color management are the same regardless of which operating system and which software you use. If you use a proprietary OS and you want to try any of the concrete examples provided in the articles, most free/libre imaging software also runs on Windows and Apple. The only difficulty you might encounter is with some of the command line examples, as the exact syntax does vary slightly from OS to OS.
Why does this website focus exclusively on free-libre image editing software? I have no particular philosophical quarrel with proprietary editing software. But I do object to the idea that the artist's own work should be locked into a proprietary file format such as PhotoShop's PSD. Adobe's move to the cloud has made this issue of who controls access to the artist's work crucially important. The Creative Cloud license agreement itself is onerous and one-sided. Once the artist stops paying the subscription fee, she loses access to the software that unlocks the proprietary PSD format that contains her creative work.
Articles & Tutorials on Color Management and Photography has links to all the color management and image editing articles on this website, arranged by the following topics:
- Tutorials on ICC Profile Color Management
- Calibrating and profiling your monitor
- Profiling your digital camera
- Choosing the right RGB Working Space
- Interpolating camera raw files
- Digital Asset Management
- High bit depth GIMP
- Painting, photography, and combining painting with photography
The About page has a little bit of information about why I switched to using Linux and started the Nine Degrees Below website, and the Galleries have a few of my photographs.
Using, discussing, and supporting Free/libre software
If you use free/libre software, then support free/libre software!
Free/libre software doesn't write itself, and if you use free/libre software, there are many ways to contribute:
- Participate in user forums and mailing lists
- Write bug reports
- Contribute code
- Contribute documentation
- Provide financial support
Whatever way makes you happy, if you use free/libre software, please find a way to support free/libre software.
Two projects that could use some extra help: If you are looking for a way to contribute time, talent, or money, I want to single out two of my favorite free/libre software projects, both of which are crucially important to free/libre image editing:
- ArgyllCMS needs monetary contributions. ArgyllCMS is the best software there is — free/libre or otherwise — for calibrating and profiling your monitor, printer, and camera. But failing sufficient monetary support from users, Graham Gill may be forced to shut the doors on ArgyllCMS development.
- GIMP needs programmers. High bit depth GIMP is almost here, and many people are already using 2.9 (the development version of the first official release, which will be 2.10). But there are too few developers. So if you can program and you have a desire to see GIMP morph into the best possible high bit depth image editor, now's a good time to pitch in and help.
If you use the Windows version of GIMP, here are a couple of cold hard facts: (1)GIMP is a native Linux application; (2)The only way free/libre software that's native to Linux gets ported to and kept running properly on Windows, is if a Windows developer steps up to the plate and takes on the responsibility for porting, building, testing, and fixing Windows-specific bugs for that software. GIMP currently doesn't have any Windows developers, so if you are a Windows developer, now is a great time to pitch in and help.
If you aren't a programmer, there are many other ways to contribute to GIMP development, such as helping to debug the code (this just means using GIMP 2.9 and making good bug reports), and helping to update the massive amounts of documentation.
PIXLS.US — A new and very different forum
Free/libre software has many amazing forums and mailing lists for discussing particular softwares, for example the Krita forums and the digiKam, GIMP, and ArgyllCMS mailing lists.
These forums and mailing lists are wonderful places to discuss using the various softwares. But they all have one thing in common: they focus on using one particular software.
Since first starting to use free/libre software for image editing I have felt the lack of a forum for discussing image-making issues that transcend using any specific software. Pat David saw this same lack, and unlike me, he actually did something about the situation and started the PIXLS.US website and forums.
Although PIXLS.US initially focused on photographers using free/libre software, Pat realized that digital painters also need a good home for discussions that go beyond how to use specific free/libre softwares. So now PIXLS.US has a forum for digital painting, or speaking more generally, art outside photography. So whether you are a digital photographer, a digital painter, or you make images that don't fit very well within these somewhat constraining categories, head on over to PIXLS.US and introduce yourself — you'll find like-minded people and a nice place to discuss whatever's on your mind (well, at least if it's related to making images using free software, but there's also a forum for discussing topics outside painting and photography).
Recent and featured articles and tutorials on the Nine Degrees Below website
- Leaves in May — A tutorial on making an illustration from a photograph.
This tutorial explains a method for making an illustration rendering from a photograph. One of the steps produces a nice line drawing. So really this is two tutorials in one. I included notes on choosing the right RGB working space for the task at hand. So maybe it's three tutorials in one.
- Default high bit depth GIMP 2.9 compared to Elle Stone's patched GIMP ("GIMP-CCE")
My patched GIMP is targeted at users who want to edit in RGB color spaces other than sRGB and have acquired (or want to acquire) a working understanding of ICC profile color management and the basics of radiometrically correct editing. My patched GIMP also contains enhanced editing capabilities such as expanded LCH editing options, the very important Luminance blend mode, and selected additional unclamped layer blend modes, that haven't yet been incorporated into default GIMP.
- White balancing camera-saved sRGB jpegs that were shot using the wrong camera white balance
sRGB is not the right color space for white balancing camera-saved sRGB jpegs that were shot using the wrong camera white balance setting. Better results can be obtained by editing your images in a linear gamma version of the Rec.2020 color space.
- How to Make a Better Custom Camera Input Profile that's also an RGB Working Space
This article shows how to use ArgyllCMS and a target chart to make a better general purpose custom camera input profile that is color balanced and normalized. The resulting camera input profile is well behaved and so can also be used as an RGB working space for editing your interpolated raw files.
- A tutorial on GIMP's very awesome LCH Blend Modes
This tutorial introduces the very awesome GIMP LCH blend modes and provides examples using the LCH blend modes first to repair a color image, and then to colorize a black and white rendering of the repaired color image. Results using the LCH blend modes are compared to results using the old HSV blend modes.
- Models for image editing: Display-referred and scene-referred
This article explains the similarities and differences between display-referred and scene-referred image editing. Even though the two models serve very different image editing goals, both models work with bounded RGB data. Display-referred RGB data is bounded by Color, which is to say by both Luminance and Chromaticity. Scene-referred RGB data is bounded only by Chromaticity.
- Color Management Experiment Kit: If seeing is believing, how much does your monitor profile matter?
There are two approaches to learning anything: Learn theory and then try to apply it. Or (my preferred approach) start experimenting and worry about theory later.
This 'Color Management Experiment Kit' is for exploring the difference a monitor profile makes in what you see on your monitor screen. It has ICC monitor profiles to play with, experiments to try, and images to try them on. Think of it as the digital darkroom equivalent of being handed a kid's chemistry set, except the only thing you'll risk blowing up is a few pixels.
- Limitations of unbounded sRGB as a universal color space for image editing
Unbounded sRGB can be used to encode and display any RGB color. Nonetheless, unbounded sRGB is not suitable for use as a universal, "one size fits all" color space for image editing. Many editing operations are chromaticity dependent, giving different results in different RGB working spaces. Choosing the right working space for the task at hand is the photographer's first, and critically important, technical and artistic decision.
- Completely Painless Programmer's Guide to XYZ, RGB, ICC, xyY, and TRCs
This tutorial was written in the hope that it might be of use to technically savvy people who know a whole lot about the code and the mathematics that goes into making an image editing program, but perhaps not so much about color spaces and ICC profiles. It also serves as a pretty good high-level overview of color science for non-coders.
- Will the Real sRGB Profile Please Stand Up?
There's only one sRGB profile, right? Wrong! I compared 15 widely used sRGB matrix profiles distributed by/with a variety of profile vendors and imaging software, and found quite a bit of variation from one sRGB profile to the next. In this article I explore the differences between the sRGB profiles variants and point out the practical digital darkroom consequences.
- Profiling Your Monitor — popular confusions, hopefully cleared
Big changes are taking place in open source color management, including whether, how, and what happens when a system monitor profile is set. The monitor profile your editing software uses determines what you see on your screen. So now is a very good time to learn more about monitor profiles.
If you are not really sure what the difference is between calibrating and profiling a monitor; if you've heard the words "vcgt tag" but don't know what it means; or if you'd like to know what a system monitor profile is, this article is a place to start.