Most of the articles on this website are about practical color management in the digital darkroom. Other articles discuss topics like raw processing, digital asset management, monitor profiling and even how to build Gimp from git. Although the principles of color management and digital photography are the same regardless of which OS and which software you use, the articles on this website assume that you use Linux and open source imaging software. If you have questions or comments, I'd love to hear from you, even if you run one of those other operating systems ;).
- A Review of FLOSS Raw Processors, Part 2
Part 2 of my review of free and open source raw processors compares interpolated output from darktable, Photivo, Rawtherapee, and my floating point version of dcraw. All post-interpolation image enhancements are disabled for Part 2 of this raw processor review, so the comparisons focus strictly on the raw processors' capabilities qua raw processor. Part 2 also considers the question of useability.
- A Review of FLOSS Raw Processors, Part 1 (revised and updated)
Part 1 of my review of free and open source raw processors is comparison of seven free and open source raw processors — dcraw, darktable, the digiKam raw processor, Photivo, Rawstudio, RawTherapee, and UFRaw — "by the specs", without looking at actual interpolated output. The review only considers features relevant to radiometrically correct raw processing and not other features such as image enhancing algorithms or digital asset management.
- What Makes a Color Space Well Behaved?
Standard RGB working spaces are suitable for image editing because they are well behaved. The color spaces defined by camera input, printer, and monitor profiles are almost never well-behaved. So what makes a color space well behaved?
- What do Clipped Colors from ICC Profile Conversions really look like?
You've been told that converting an image from one color space to another can result in clipped colors. But how, why, and where does the clipping actually happen? This article shows you a real-world example of clipped colors in the image itself, in the image color gamut as seen from inside the CieLAB reference color space, and in the image's individual red, blue, and green channels.
- What is embedded color profile information?
Color-managed image editors like Gimp, Krita, and Showfoto expect to find embedded color profile information in the metadata of every image that is opened for editing, and if they don't, they ask you what to do about this unfortunate situation. For anyone who might not know exactly what embedded color profile information really is and why some images don't have any, this page offers a brief explanation.
- Can today's LCD monitors display all the colors in an sRGB image?
While perusing the various photography forums, sometimes I run across the claim that when shooting raw, if you convert the interpolated image to sRGB, you can see all the image colors on your monitor. Fifteen years ago, in the heyday of CRT monitors, anyone using a reasonably high quality, properly calibrated CRT monitor could say with confidence "Yes, my monitor can display all the colors in an sRGB image." Is this claim still true if you are using an LCD monitor?
- Build Gimp 2.9 from git, Gimp 2.8, and Gimp 2.6, each in its own prefix
This guide shows how to build and install multiple versions of Gimp — Gimp 2.9 from git, Gimp 2.8, and Gimp 2.6 — on 64-bit OpenSuse 12.2, with each version of Gimp in its own separate prefix. When you are finished, you can run all three versions of Gimp, even at the same time.
Specific information on this page applies to 64-bit openSUSE 12.2 and is current as of January 21, 2013. The general process should be valid for most flavors of Linux, for the reasonably foreseeable future.
- LCMS2 Unbounded Mode
When Marti Maria rewrote LCMS to produce LCMS2, his motivation wasn't just to accomodate V4 ICC profiles: he designed LCMS2 to work in "unbounded mode". Unbounded mode ICC profile conversions eliminate interim clipping from color space encoding limitations. And when using linear gamma profiles at 32-bit floating point image precision, along with an appropriate output format, magic happens.
- Linear Gamma vs Higher Gamma RGB Color Spaces:
Gaussian Blur and Normal Blend Mode
Technically speaking, RGB color mixing should always be done in a linear gamma color space. When you blur or use the normal blend mode to mix colors in the regular sRGB color space, the resulting color is darker than it should be and sometimes acquires a noticeable color cast.
This article is the first of a planned series of articles on editing in a linear gamma color space. Upcoming articles will examine channel mixing, converting a color image to black and white, applying curves, and using different blend modes.
- Will the Real sRGB Profile Please Stand Up?
I compared 15 sRGB (matrix) profiles used by a variety of open source image editing programs and found quite a bit of variation from one sRGB variant to the next. In this article I explain the differences between the sRGB profiles variants and I point out the practical, digital darkroom consequences.
Even though Hewlett-Packard and Microsoft proposed the sRGB color space as a way to eliminate color management, today you need color management just to manage the proliferation of sRGB profiles.
- sRGB, the universal monitor profile, not so good for LCD monitors
LCDs and CRTs — color-wise, they are very different beasts. If you are using sRGB as your LCD monitor profile, you might want to reconsider: sRGB was designed for use with CRT monitors. If you have an LCD monitor, sRGB is not likely to be a good enough match.
- All the Colors, Some of the Colors, the Colors of Daylight
What's that funny horseshoe thing? It's all the colors in the world.You use color space profiles every day in your digital darkroom. If you'd like to know more about what a color space profile is, read on.Our specimen color space profile will be the ubiquitous and historically interesting sRGB.
- 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.
If you are a software developer and you mistakenly think that making and using more than one monitor profile is just plain stupid (the esteemed Bruce Fraser would have disagreed with you), then by all means, please read this article.