Re: DICOM curve with spectraview
Re: DICOM curve with spectraview
- Subject: Re: DICOM curve with spectraview
- From: Klaus Karcher <email@hidden>
- Date: Sat, 05 Apr 2008 14:39:52 +0200
Roger Breton wrote:
But if we do chose a monitor calibration to match the RGB "gamma" or
transfer function we mostly work with, aren't we making our system less
device independent?
No -- not less device independent IMO, but optimized for the data we
mostly work with (least banding / loss off tone levels).
What about CMYK? If we use brandX CMYK more often, would you chose a monitor
calibration to match the flavor of CMYK we mostly work with?
Probably not but I read opinions on other lists that CMYK have "inherent"
supposedly "natural" or "logical" TRC? I know it sounds crazy to say that
"sheetfed printing" has a gamma of 1.8, at least on the face of it.
One can compare the TRC of a printing process with gamma curves or other
transfer functions and conjecture that converting between similar curves
results in less loss of tone levels, but there are several pitfalls:
- there is no single TRC for C, M, Y, and K -- they are different
- simply counting lost values does not account for the visual weighing /
importance of the lost steps
- simply comparing the primary TRCs falls short of the complex relations
between RGB, CMYK and our vision. E.g. the loss of a certain tone level
in the Y-channel of a CMYK image might be completely invisible in a pure
yellow gradient, but distracting in a gray- green- or blue gradient.
Here are two plots to clarify some of the points mentioned above. They
show the normalized TRCs of C, M Y and K in FOGRA39 compared to various
Gamma functions (dashed lines) and Y(L*) (dotted, gray line).
with linear axes:
http://digitalproof.info/colorsync-users/TRCs/FOGRA39-Gamma-LStar.pdf
and with a logarithmic Y-axis:
http://digitalproof.info/colorsync-users/TRCs/FOGRA39-Gamma-LStar-log.pdf
They show that the judgment upon which of the curves go best with each
other depends on the Y-scaling.
Klaus Karcher
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden