The p-Code Machine

Recently I’ve become the proud owner of a spectrophotometer, besides profiling printers, there lots of other cool things you can do with it… For example making your own homebrew ColorChecker camera profiling target. While my replica isn’t accurate enough as a drop-in replacement, it does work very well, when each homebrew ColorChecker is measured separately to create per-chart reference data. Even with the per-chart reference data the homebrew ColorChecker isn’t as good as the original, because the original had it’s pigments selected to reduce metamerism, which the homebrew version is potentially vulnerable to.

The above picture is a first version of my homebrew ColorChecker. I made it by first looking for a good neutral matte white paper, which became Tetenal Photo Archival Matte, for which I then made a printer profile using ArgyllCMS. Generating a printer profile (actually it’s profile of the paper+ink+printer+driver configuration combo) means I can print images with a reasonable level of confidence the print will be color accurate. Then I made a custom sRGB version of the ColorChecker target (look for inspiration here). Then I printed the custom sRGB image of the ColorChecker with the printer profile applied. Then I measured the target using my spectrophotometer, so I know what colors the patches actually are. I scaled the print so that the target could fit inside the manual area of a traditional 14mm DVD case. The DVD case has a dual purpose here, first it keeps the target straight/upright and when closed it protects the target from dust/moist. To stick the target to the inside of the case I used 3M Photo Mount, which is Ph-neutral to prevent the glue from deteriorating the colors.

Initial tests are very encouraging, camera profiles generated from it work quite well, especially when shot using a decent hot-shoe flash.