Wire ~ wrote:
Hi,
When working with the target, I've found scanin to be incredibly touchy about
getting a mapping. A
crop difference for a fraction of a percent can make a difference, and scanin
will reject what look
like perfect fit from the diagnostic output TIFF. I've seen this problem
discussed in the forums
from 10 years ago with no clear answer, except that when users futz around
with adjusting the crop
it eventually can me made to work. I haven't tried to debug it, but it's a
major PITA. There is
some edge case which throws scanin and it's not grokkable based on factors
under the user's obvious
control.
After I got scanin to accept the targets, I noticed was very large peak
errors in profile
generation with the Nikon — like 25 dE or sometimes higher. The Epson peak
error is about 9. At
first I thought this might be caused by large amounts of bloom in the shadows
with the Nikon, due
to very dirty optics. This old Nikon mosdef needs to be cleaned. But the
worst error patches are
not darks next to brights, as I had suspected. The worst errors are in blues
in the second target.
Especially at patch G38, in the blues that surround this patch, and the cyan
group above. (The
histogram from profcheck shows a pronounced hump with a very distinct
separate tail.)
It seems that the Nikon and Epson see very saturated blue component very
differently and this
affects colors all over the map, especially yellow :).
My explanation to myself so far is that Epson sees a blue that the Nikon
designers might have
punted on because the know that most displays will not show it. I haven't yet
compared a map for an
Epson 4800 printer but I have printed a corrected IT8 side-by-side and while
the colors are
distinctly different, neither makes the other look wrong. They just have
different personalities.
Am I on the right track with my thinking? Is it known, for example, that the
filters Nikon applied
made such a compromise on blue response, and that a large peak error in blues
comes with the
territory of some scanners and cameras?
