X3F Tool with full colour profiling

Started Feb 10, 2010 | Discussions thread
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Chris Rijk
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X3F Tool with full colour profiling
Feb 10, 2010

This is a follow-up from this post, but it's interesting enough to deserve a new thread:
http://forums.dpreview.com/forums/read.asp?forum=1027&message=34482131

The "experimental" (as in "beta") version of X3F Tool from the link above now has support for colour profiling (and also area based white point selection). This is a much more than simply choosing white balance - ideally, you'd want to do a full spectrum analysis over the light, but that's a bit tricky with just a camera. But, with a reference colour chart, you can get closer.

I've been using the X-rite Colour Checker for the base profiling in the first place, so it turned out to be reasonably easy to adjust the profiling with reference to an image with the card in it.

Let's start with an example:

The above image is a particular X3F file processed with the default colour profile in X3F Tool (which is calibrated to strong sunlight on my SD14). The colours are a bit off - if you do a right mouse click over a particular colour patch, and select the "Profile point..." option, you'll see that they don't map that well to the reference points in the Profile Viewer.

First of all, we can do a basic white balance correction - again, move the mouse to a particular point on the image and do a right mouse click (or ctrl-click) and choose "Set white point area". It's best to choose one of the middle grey patches. Using "Set white point area" will generally give better results than "Set white point" since it averages across multiple pixels - but then you do need a uniform region to select on.

The above image is after using "Set white point area". The colours are better, and checking with "Profile point..." gets closer. But it's still not quite right.

Doing a full colour profile takes a few discrete steps, as described here:
http://www.x3f-tool.org/features/profiling.html

After that, you get results like this:

The changes aren't too dramatic because the light wasn't that far off sunlight. You might see bigger differences under artificial lighting. However, it helps to have your Colour Checker chart under the exact same lighting conditions.

There's more examples here:
http://chrisrijk.smugmug.com/Comparison-shots/Colour-profiling/11196710_H36Mp

Please note that this work is EXPERIMENTAL. It has only gone through the most BASIC TESTING. It is a WORK IN PROGRESS. That's why it's a separate download.

But it might be useful

You can download the X3F file in above example here:
http://www.x3f-tool.org/raws/SDIM1538.X3F

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