Problem applying Profile to Profile
Problem applying Profile to Profile
- Subject: Problem applying Profile to Profile
- From: Tim Vitale <email@hidden>
- Date: Mon, 15 Jul 2002 14:46:40 -0700
Having created a reasonably successful printer profile for a specific
printer (Epson 1200) using a specific ink-set (Generations) for a
specific paper, I then apply it to the image using Profile to Profile in
PS 5.5 and print the image; usually successfully. However, I have been
having some problems recently.
This is what I've observed:
Concentrating on the problem area, the image's whites' (with a slight
mottled texture), the white area has generally equal RGB values,
reflecting that the region is neutral white. Selecting a reasonably
uniformly white region and then making 3 test measurements (on screen
using "Info"), the results show that the R, G & B values vary 0-2 within
a measurement, and, +/- 3 across the area measured (it mottled). After
applying the a new profile using P to P, a new set of measurements (made
in the same region using X & Y values from "Info") shows that the R, G &
B values are now separated by 5-12 units across R, G and B, but are
still about +/- 3 (when R, G & B values are averaged) between the three
measured areas.
I have experimented with using several different types of profiles when
applying the P to P transformation, thinking that maybe a specific
profile was at fault. The absolute numbers change as expected, but the
variation across R, G & B is approximately the same.
I also experimented with a Macbeth gray scale scan, and found even
greater variations across the R, G & B values. This was probably
because the initial RGB values were not as close (2-4 unit variation) as
the neutral white of the "image" example.
Is this the fault of (1) my method of applying P to P, (2) the way PS
5.5 applies P to P or (3) something that is inherent to ColorSync. That
is, when applying one set of transforming numbers (printer profile) to
another set (the image), variations are introduced that can't be
avoided.
Tim Vitale
Paper, Photograph and Electronic Media Conservator
Emeryville, CA
510-594-8277
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