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Articles and tutorials on ICC profile color management and free/libre image editing

The philosophy behind the Nine Degrees Below articles and tutorials

The first assumption on this website is that you want to understand enough about color management to make your own intelligent decisions. Too many articles on color management just assume that all the reader really wants to know is which buttons to push.

The second assumption 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 and image editing are the same regardless of which operating system and which software you use. So 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.

Ponte de Amazade bridge
Ponte de Amizade — processed using RGB "plate" replacement

Why does this website focus exclusively on free-libre 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.

What's on the Nine Degrees Below website?

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. Below is a summary of the articles and tutorials on this website:

Articles & Tutorials on Color Management and Image Editing has links to all (well, almost all) of the articles and tutorials on this website, arranged by topic. Here's an overview:

  1. Tutorials on Practical ICC Profile Color Management in the Digital Darkroom.
  2. Calibrating and profiling your monitor.
  3. Choosing an ICC RGB Working Space
  4. Profiling your digital camera.
  5. Working with Camera Raw Files.
  6. Stacked ev-bracketed raw files for clean shadows and intact highlights
  7. Digital Asset Management using digiKam and Exiftool.
  8. High bit depth GIMP 2.10, including articles on using GIMP's new LCh and Luminance blend modes.
  9. Using GIMP's LCh blend modes to repair and split-tone a photograph
  10. Painting, photography, and combining painting with photography.
  11. Painted using Krita and high bit depth GIMP

If you use free/libre software, then support free/libre software!

Free/libre software doesn't write itself. There are many ways to contribute:

  • Participate in user forums and mailing lists
  • Write bug reports
  • Contribute code
  • Contribute documentation
  • Provide financial support

If you are looking for ways to contribute time, talent, or money to free/libre software, 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 could use some additional programmers. GIMP is developed on Linus, so Linux programmers are always welcome. It would also help if a few Windows programmers would volunteer to assist in porting GIMP code to and debugging GIMP code on Windows.

    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 and making good bug reports), and helping to update the massive amounts of documentation.

Featured Nine Degrees Below articles

These "featured articles" are here mostly to give you an idea of what sort of information is on this website. Articles & Tutorials on Color Management and Image Editing (which you can access by clicking on the "Articles" tab at the top of any page on this website) has the full list of Nine Degrees Below articles and tutorials.

  • Making a useful LCh color palette

    GIMP color management settings for the color management experiments.The LCh color wheel provides a useful framework for organizing and choosing colors, and allows to access the treasure-trove of colorimetric color information available on the internet. Links are provided to some nice articles for skin colors and flower colors. The tutorial also provides a set of downloadable LCh-based color palettes for use with GIMP.

  • Limitations of unbounded sRGB as a universal color space for image editing

    Two versions of a car show photograph showing that correcting a color cast in the wrong RGB working space produces wrong results.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. 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

    ICC profile xicclu and tone response curves.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?

    Temple on a misty day.In theory there's only one sRGB ICC profile as defined by the sRGB color space standard and the ICC values for the D50 illuminant. In practice, there's considerable variation from one sRGB profile to the next. In this article I explore the differences between the sRGB profiles variants, point out the practical digital darkroom consequences, and conclude that the "one true sRGB profile" is the one distributed by ArgyllCMS.