I did a little playing with dcraw to tiff and ppm and I was shocked at how different they are from the jpegs. I would think shooting color ramps, measuring, and fitting the results to curves might be close to what you're talking about.
This is something I was working on for printer calibration before I gave up and bought a Color Munki. I'm not sure I finished a parser for reading back the printed out versions from a scan. Linearity and the range of actual colors would be an issue. I think I was looking at the mixing that happens here because printers use cmyk and I was trying to look at rgb, so whenever I'd ramp up one color others would go along with it. Some of that might have been to create a value change. I'm not sure my parser works, I may have been using the eyedropper in gimp and entering the numbers manually. The plot is from Gnuplot. It was partly seeing jpeg artifacts in my photos of the printed grid that convinced me I wanted to do RAW. The grid was made by writing into an array in memory then writing that array out as an image. The font was stolen from giflib or libgif. On 9/30/15, Greg Troxel <g...@ir.bbn.com> wrote: > > Alan Corey <alan01...@gmail.com> writes: > >> OK, never mind. I thought the white balance settings were getting >> reset between one RAW file and the next but I tried it again and they >> don't. So as Greg says I can load a gray card image, use the >> eyedropper, hit Cancel and load the real image. So my programming for >> recreation will go back to making custom hyperfocal tables. > > It would be a real contribution to understand the calibration from raw > to JPEG so that we could more or less reproduce the camera > transformation. I'm not saying that's right, but it would be a nice > reference point. I find that with nikon bodies, I need significant + > exposure compenation in ufraw to match the jpegs. > -- Credit is the root of all evil. - AB1JX
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