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CIEXYZ and CIELAB are colour-spaces designed to roughly fit with human luminance and colour perception.

CIEXYZ images are essentially cone-catch images where the sensitivites are described by the CIE X, Y and Z receptors (which are hypothetical receptors designed to fit with human colour discrimination behaviour, corresponding to longwave, mediumwave and shortwave respectively).

CIELAB images can be created from CIEXYZ, where L describes the luminance channel, A describes a colour opponent channel between red and green, and B describes a second colour opponency channel between blue and yellow. This fits with various theories of how human colour vision works, though is by no means a perfect model.

The micaToolbox can be used to create and convert images to CIEXYZ and CIELAB colour spaces, so that these can in turn be used with all the other features of the toolbox.

  1. Create a cone-catch model for your camera using the “CIE XYZ 1931 400-700” receptors.
  2. Load an mspec image and run: plugins > micaToolbox > Convert to Cone Catch and select the model you’ve just created to make a CIEXYZ image.
  3. To convert to CIELAB run: plugins > micaToolbox > Image Transform > XYZ to CIELAB 32-bit
CIEXYZ and CIELAB