On Sep 18, 2015, at 1:27 PM, Spinnaker Photo Imaging Center <spinnakerphotoimagingcenter@dnmillerphoto.com> wrote:
Ben, for years you have written about home brew CC. I have never tried it since I would not know what color to purchase….oil, or watercolor, or pastels.
I would not know how this home brew chart could be read. Or what to read it with.
If it's an actual 24-patch ColorChecker, unless you're going to be making it in volume, buy the real deal. If you'll be making them in volume, take your ColorChecker to the local home paint store (be sure it's a new one with an expanded gamut) and have them match the patches on their own color matching system; they'll mix up spectral matches for you using their own X-Rite branded hardware and software. If you plan on doing that for other than personal / internal use, run it by a lawyer; I've no clue what X-Rite's own lawyers might think if you started selling them. But, if you want to sell charts...the patch selection of the original ColorChecker is good but certainly can be improved upon; you'd be much better off making something original. If you want an high-patch-count chart with a large gamut and lots of interesting spectra, go to the local art store and buy lots of paints and some brushes and so on and paint a bunch of squares. Mix the paints in as many permutations of proportions as you've patience for -- and be sure to do multiple tints, especially of the darker colors, to bring up the chroma. Golden Fluid Acrylics is a good choice. Or, enlist the help of a local artist who's already got an extensive palette. In either case, you'll need to measure the patches with a spectrometer (such as an i1 Pro). For the homebrew chart, you'll also need to create the necessary chart recognition files for your profiling software. With Argyll, it's straightforward but the file format is very unforgiving; if it doesn't work right, it's because there's something not right in the files, and it may take some careful inspection to spot where you've gone worng. If you're going the homebrew route...don't think you have to make a single oversized chart with lots of teeny tiny patches to get a good patch count. A much better approach is multiple charts with large patches; combining the readings from multiple charts into a single input file for color profiling is trivial -- at least, it is with Argyll. Were I to do it again...I'd probably do 8" x 10" charts with ~1" patches = 80 patches / chart, and then make however many charts (each with a different selection of paints) as I felt inclined to make. If you're feeling extra inspired, you can make an overlay cutout like on the ColorChecker charts, either by hand with a razor or with a computerized paper cutter such as is popular amongst the scrapbooking crowd. Or you could start by putting down some masking tape to outline the patches, and discard the masking tape when done. Either method will make it much easier to get good clean straight edges to help the edge detection algorithms identify the chart's location and orientation. But, even if not, you can digitally overlay a similar mask in Photoshop or Affinity Photo or the like before feeding the picture to the profiling engine. But...again, chart-based profiling is suboptimal in many ways, and not at all what I do today.... Cheers, b&