Articles and tutorials on ICC profile color management, plus articles on selected free/libre image editors and raw processors

This page has links to all the Nine Degrees Below articles and tutorials on color management and image editing, arranged by topic. Check the Gallery and the About pages for articles and essays on topics not directly related to working in the digital darkroom.

Tutorials on Practical ICC Profile Color Management in the Digital Darkroom

For a complete newbie, it's probably best to read these tutorials in the order listed below:

  1. Pictures of Color Spaces Inside CIELAB

    When learning about color management, "light dawns gradually over the whole". So read the article, look at the pictures, and don't worry too much about understanding every single little detail. You'll get the gist and that's what's important. The same advice applies to all the articles in this section.

  2. Color Space Profiles: All the Colors, Some of the Colors, the Colors of Daylight
  3. The difference between "Convert" and "Assign"

    The difference between converting to a new profile and assigning a new profile is critically important to understanding ICC profile color management. Suggestions for improving this article (and of course all the other articles) are very welcome.

  4. What is Embedded Color Profile Information?
  5. What are 'Clipped Colors' from ICC Profile Conversions?
  6. digiKam/showFoto Settings for Color Management: Behavior Tab.

    Although this article discusses the digiKam/showFoto color management settings, the considerations apply equally to all image editors. So if you don't know what settings to choose in your image editor's color management settings dialog, this article can help you figure it out.

  7. ICC Profile Conversion Settings: GIMP, Krita, digiKam/showFoto, Cinepaint. This article is partially outdated article — Krita and GIMP settings have changed somewhat — but the digiKam/showFoto and Cinepaint settings are still the same. You might find the overview of how very differently image editing programs handle the various profile conversion settings to be helpful when assessing the settings provided by your favorite image editing programs.
  8. ICC Profile Conversion Intents.

    This article explains the four conversion intents (relative and absolute colorimetric, perceptual, and saturation). It also explains why perceptual intent usually doesn't prevent the clipping of out of gamut colors.

  9. Programmer's Guide to XYZ, RGB, ICC, xyY, and TRCs.

    This article presents ICC profile color management from the point of view of basic color science, in the process summarizing and reviewing much of the material presented in the articles listed above. If you aren't a programmer, don't let the title scare you! Many times software programmers aren't as well versed in color management as they'd like to be. So this really is an introductory article despite the scary title.

Calibrating and profiling your monitor

If your monitor isn't showing you accurate colors, then color management isn't all that useful.

  1. Calibrating and profiling Your Monitor — Popular Confusions, Hopefully Cleared

    This article isn't a "how to". Rather it explains the basic concepts so when you read a "how to", you'll know what the "how to" is actually talking about. Also there is a great deal of misinformation about monitor profiles floating around free/libre software forums and mailing lists; this article will help you cut through the confusion.

  2. Color Management Experiment Kit: If seeing is believing, how much does your monitor profile matter?

    If you don't use color management, or if you think sRGB is "good enough" as a monitor profile, here's some quick and simple "color management experiments" to try — all you need is GIMP and the downloadable experiment kit.

  3. History of the Very Odd sRGB Color Space (you need to calibrate your monitor even if sRGB is the only color space you use).
  4. sRGB, the Universal Monitor Profile — Not So Good for LCD Monitors
  5. How much of the sRGB color gamut can be displayed on your LCD monitor?
  6. Viewing Photographs on the Web

Profiling your digital camera

  1. How to Make a Camera Input Profile Target Shot
  2. How to Make a Better Custom Camera Input Profile
  3. When profiling your camera with ArgyllCMS, what type of camera input profile should you make? An earlier version of this article appeared under the title "Five Camera Input Profiles Applied and Compared".
  4. Color Science History and the ICC Profile Specifications
  5. ICC Color Space Profiles and Blue Channel "Noise"

Choosing the right ICC RGB Working Space

Surveys and specifications

  1. Will the Real sRGB (matrix) Profile Please Stand Up?
  2. Survey of Free and Open Source ICC RGB Working Space Profiles
  3. From sRGB color space to sRGB ICC profile: A worked example showing how to use Bradford chromatic adpatation to calculate the ICC D50-adapted sRGB profile primaries from the sRGB color space specifications
  4. The Luminance of an sRGB Color: color management by calibration vs ICC profile color management. This article is not quite finished and I don't know when I'll get around to finishing it. Nonetheless, it's got some interesting information.

Well Behaved RGB Working Spaces

  1. What Makes a Color Space Well-Behaved?
  2. Are Your Working Space Profiles Well Behaved?
  3. In Quest of Well Behaved Working Spaces
  4. Elle Stone's Well-Behaved ICC Profiles and Code

Choosing an RGB working space

  1. sRGB as an RGB working space
    1. White balancing camera-saved sRGB jpegs that were shot using the wrong camera white balance
    2. Photographic colors that exceed the very small sRGB color gamut
    3. In a world full of large color gamut devices, what is sRGB good for today?
  2. Linear gamma and perceptually uniform RGB Working Spaces
    1. Gaussian Blur and Normal Blend Mode in linear gamma vs perceptually uniform RGB working spaces
    2. Is your image editor using an internal linear gamma color space?
  3. Working in bounded and unbounded color spaces
    1. Models for image editing: Display-referred and scene-referred
    2. LCMS2 Unbounded Mode
    3. Limitations of unbounded sRGB as a universal color space for image editing
    4. Multiplying out of gamut colors in unbounded RGB color spaces produces meaningless results
    5. Color correction fails in unbounded sRGB

Interpolating camera raw files

  1. A Review of FLOSS Raw Processors, Part 1, comparing 7 raw processors "by the specs"
  2. A Review of FLOSS Raw Processors, Part 2, comparing 4 raw processors according to useability and quality of output
  3. dcraw C Code, Outlined and Annotated
  4. dcraw UnDnged: Modify dcraw to Use Your Own Custom Camera Profile
  5. Floating point dcraw + DCB, AMaZE, LMMSE, AFD, & VCD
    1. Part 1: What Software was That?
    2. Part 2: How to Use dcraw-float
    3. Part 3: Overview of the dcraw-float Floating Point C Code
    4. Part 4: The Legal Stuff — dcraw-float License, Limitations, Source Code
  6. UFRaw: Are the Highlights in Your Raw File Really Blown? This bug affects UFRaw versions 0.16 through 0.20 (current as of March 2015).

Digital Asset Management

  1. ExifTool Commands Every Photographer Should Know
  2. Digital Asset Management using digiKam and Exiftool: cleaning up messy metadata
  3. Digital Asset Management using digiKam, Geeqie, and Exiftool: ingestion

High bit depth GIMP

  1. Building GIMP
    1. Build GIMP in a prefix for artists and photographers
    2. Update GIMP in a prefix for artists and photographers
    3. How to build GIMP-CCE, a version of high bit depth GIMP that's patched to allow editing in any well-behaved RGB working space
    4. Build GIMP 2.9 from git, GIMP 2.8, & Gimp 2.6, each in its own prefix (older article, but still has some relevant information)
  2. Tutorials on using high bit depth GIMP
    1. User's Guide to High Bit Depth GIMP 2.9 Color Management
    2. Making a perceptually uniform step wedge using GIMP. If you've never used high bit depth GIMP (or even if you've never used GIMP at all), this is an introductory tutorial that produces something useful.
    3. Tone mapping and shadow recovery using GIMP's 'Colors/Exposure'
    4. A tutorial on GIMP's very awesome LCH Blend Modes
    5. LAB Lightness to black and white using GIMP 2.8. This article shows mathematically correct and incorrect ways to convert a color image to black and white using the LAB Lightness ("L") channel from GIMP 2.8's "decompose to LAB". If you don't read this article first, you probably won't understand the next article listed below.
    6. LAB Lightness to black and white using GIMP 2.9 and PhotoShop. This article shows mathematically correct and incorrect ways to use the LAB Lightness channel to convert a color image to black and white when using GIMP 2.9, explains the relationship between LAB Lightness and RGB Luminance, and summarizes mathematical mistakes behind the typical PhotoShop tutorial on using LAB Lightness to convert to black and white.
  3. Tutorials on using GIMP-CCE
    1. Default high bit depth GIMP 2.9 compared to Elle Stone's patched GIMP ("GIMP-CCE")
    2. Autumn colors: An Introduction to High Bit Depth GIMP's New Editing Capabilities
    3. Photography Workflow using GIMP-CCE as the primary image editor
  4. Miscellaneous
    1. A Review of 'The Book of GIMP'

Painting, photography, and combining painting with photography

  1. Urn in a Window: A painting in progress, using a workflow that can also be followed when colorizing or split-toning black and white photographs
  2. Combining painting with photography. Much of my inspiration for wanting to combine painting and photography comes from studying Pictorialist photographs from the late 19th/early 20th century. This article illustrates several approaches that I've been exploring as ways to incorporate painting with photography.
  3. Painting and blending colors using Addition, Subtract, Divide, and Multiply blend modes. This article uses digital "glazing grids" to demonstrate the various ways RGB colors can be mixed in the digital darkroom or painting studio, and then shows the layer stacks for two paintings done using Addition, Divide, and Multiply layer and brush blend modes.
  4. 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.
  5. Exploring the LCH and HSV blend modes using a Wikipedia photograph of Kenyon Cox's portrait of Saint-Gaudens: This tutorial: (1)uses the Wikipedia photograph of Cox's portrait to compare the LCH and HSV blend modes; and then (2)takes a quick look at the photograph's hues and dynamic range, at which point it becomes obvious that the Wikipedia photograph is pretty but very far from colorimetrically accurate.