Hi list
In the past we had several discussions about the optimal gamut of matrix
based RGB-profiles as workings space for Photoshop ans other imaging
applications.
Matrix based working spaces are representing a virtual monitor with
additive color mixing. The print process is made by subtractive color
mixing.
So the gamut of matrix based RGB-Workingspace is always very different
to any printing working space.
At the moment I know about two projects which are working on a
RGB-working space, which has gamut according to a wide gamut printing
process and an ideal RGB greybalance.
One is the project
http://www.photogamut.org which is now only available
in german language, but at the end of next week also in english
And the second project is the "reference medium gamut" of the ICC
The ICC project "reference medium gamut" as I understand it now, will
change a lot, how gamut mapping will be done in the future with
ICC-profiles.
Today, the calculation of the gamut-mapping for the perceptual intent is
a secret of every vendor of ICC-profiling software.
Mapping High-Gamut RGB-Images to a printing space with perceptual
mapping results to differnt results in the saturated colors and to
different tonal adjustments.
The concept of a "reference medium gamut" gives two advanteges:
First, only very saturated colors, which are even not printable with
wide gamut printing processes will get some slight gamut mapping.
If all color corrections and image optimizations are done in this
colorspace, a relative colorimetric match (may with blackpoint
compensation) to the target printing space will lead to very good
results. The problem of blue turns purple or red turns to orange is
minimized.
For printing processes with a very small gamut, the "reference medium
gamut" is a reference for calculating the perceptual mapping.
As the normal perceptual mapping is calculated also for very big source
gamuts, this new approach should result to a perceptual mapping, which
is not compressing too much normal saturated pictures.
In the next step, not only pictures but also spot colors are represented
inside the reference medium gamut.
So pictures and spot colors can be alway mapped with the same gamut
mapping strategy, which makes wokflows for the complete document much
more simple.
At least, the reference medium gamut makes it possible to go big steps
forward in the field of quality control for color management workflows.
With a set of reference pictures and technical elements, it is possible
to make visual inspections, if the gamutmapping from the reference
medium gamut to the most used printing spaces (eg. SWOP, GRACoL,
ISOcoated, Newspaper etc...) gives the results we are expecting.
In germany, there is next week a meeting about standards and qality
control for digital photography at the DIN (German Institute for
Standards). One project is so called "Masterproof for RGB-Data" which
allows photographers to deliver data in a standardized RGB-Workingspace
with printing gamut and a printed proof of this data including a digital
control strip for control-measuring the proof with a spectrophotometer
like the EyeOne.
A first prototype of the control strip and the possibility to use the
free gretag macbeth measuringtool for the RGB-proof verification should
be available in january.
--
Looking forward to quality control for color management workflows
:-) Jan-Peter
--
colormanagement.de ---------- fon/fax +49 30 611 075 18
Jan-Peter Homann ------------- mobile +49 171 54 70 358
Kastanienallee 71 -------
http://www.colormanagement.de
10435 Berlin --------- mailto:homann@colormanagement.de