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:
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:
Cheers,
b&
