When I use the eye dropper tool in darktable on the top right patch (A1) I get RGB of 59,51,51. I take an image of a Wolf Faust it8 target, turn off a bunch of the default processing that darktable does, change the input, output and internal profiles to linear rec709 RGB and export to tif. I sold my Coloraid IT8.7/2 target because the Kodak photographic paper has fluorescent brightening additives.I'm trying to do a variation of the color profiling flow given in this post about color profiling They are not printed and I don’t expect there are any fluorescent whitener additives in the pigments.
The bigger ColorChecker Digital SG is expensive, but the increased number of patches may be useful for more detailed modelling (which I am yet to attempt).ĬolorChecker charts are made using multiple different pigments, giving reflective spectra that are more representative of the real world. I have found the simple and low-cost ColorChecker Classic 24 to be satisfactory for matrix profiles. For real world photography, forget about buying the “biggest and best” camera profiling target and consider more general matrix profile models. Modern DSLR cameras surpass the gamut and dynamic range of any camera profiling target. ColorChecker targets are made using multiple different pigments, giving reflective spectra that are more representative of the real world. This is a problem if the camera spectral sensitivities are different to the human eye. The processes are optimised to produce colour, usually from just three of four colourants, that look natural to the human eye but actually might be composed of quite different spectra. Metamerism is another problem for photographic and printed targets. These papers and printed camera profiling targets can show colour shifts towards blue when there is ultraviolet in the light source. Photographic papers can contain “ fluorescent whitener additives” (or “optical brightening agents”) which makes these papers appear more blue. Spectral problemsĬamera profiling targets are commonly photographed in sunlight, which includes ultraviolet wavelengths (UV). White patch deviation from perfect neutral (Delta-ab=0) for the seven targets considered in this review. Is the CMP Digital Target 4 simply a home-printed target? Surprisingly, the CMP Digital Target 4, with 570 patches, has a small gamut and is weak in blues and reds. The IT8.7/2 target provides satisfactory coverage with 288 patches. The ColorChecker Digital SG and LaserSoft DCPro targets have similar gamuts.
The HutchColor targets have the widest gamut. For the X-Rite charts I could only get Lab data and conversion to XYZ and then xyY is more involved (equations on Bruce Lindbloom’s site).Īll targets are weak towards green. The calculation of xyY is very simple from XYZ reference data. A wide gamut test chart is preferred, to exercise the camera’s response.īelow are two-dimensional gamut plots for seven targets (including two from HutchColor). Modern digital SLR (DSLR) cameras have very wide colour gamuts. Summary of camera profiling targets examined I don’t quote batch numbers for reference data because I believe the manufacturing is precise. I found reference data on the manufacturers websites for most charts. I have evaluated the following reflective targets which are supported by Argyll CMS. All targets are not equal, as you will find in this review. For this we need a profiling target (a test chart). For a long time now, I have making my own camera profiles with Argyll CMS. Third-party raw photo processing applications need custom input profiles to make nice colour from camera RGB.