On 2012-11-23, at 9:50 AM, Ben Goren wrote: > I just looked a bit closer, and I can only see a half-dozen pixels clipped in > the second green channel in patch N18, and they're all outside of the > BOX_SHRINK margins. I've done a bit more experimentation, and I'm now *VERY* confident that this has nothing at all to do with the RAW processing and everything to do with something going wonky in colprof. I've created plain flat TIFFs in various ways out of the original RAW file, confirmed that there's nothing weird in the TIFFs (no clipping of anything but the black patch, etc.), and then fed those TIFFs to Argyll, and used Argyll for all further manipulation. I've also used Photoshop to tag the image with the profile and gotten the same results. Here's a more dramatic recent example:
That's the original file tagged with the profile. You can confirm by checking the RGB values of the background -- they're all 255,255,255, but they get turned cyan by the profile. Assign any standard generic-ish profile (such as sRGB) to that image and the cyan becomes white. For reference, here's an idealized synthetically-created version of the chart. You can confirm at a glance that the chart itself is being accurately reproduced:
Indeed, if you do a blink comparator type of analysis between those two pictures, there's hardly any visible difference at all. Here's the .ti3 file, generated from a full-sized (but cropped) 16-bit TIFF of the (untagged) top image:
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Here're the two most relevant lines from that file: # XYZ_X XYZ_Y XYZ_Z RGB_R RGB_G RGB_B STDDEV_R STDDEV_G STDDEV_B I13 8.7720e-03 8.5310e-03 8.8570e-03 0.52812 0.49257 0.47701 0.19195 0.17432 0.14688 N18 94.683 98.339 81.005 53.085 53.987 52.269 6.8720 6.6649 6.7166 I13 is the light trap I described earlier, and N18 is a bit of Teflon thread seal tape. The latter is only barely above 50%, with a looooooong way to go before clipping. And here's the profile by itself, created by colprof without any options:
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Cheers, b&