[Openicc] new: Proof colour space
almccart at lexmark.com
almccart at lexmark.com
Tue May 2 11:36:31 PDT 2006
Hi Jan-Peter and all,
I would agree that it needs to be a free choosable color space that is
independent of
scanner, camera, monitor, types of RGB spaces and that is also independent
of any
particular CMYK. Note that Adobe RGB is a monitor type of RGB even though
it is
wide gamut.
Yes - I was thinking that a proofing color space would be an intermediate
between the
source color spaces [e.g., Adobe RGB, camera Raw RGB] and particular print
related
output spaces. One question is how constrained should the gamut be?
Should it be
limited to a SWOP-like gamut? Or be like the ISO reference gamut - which
is a bit larger.
Another way of thinking about it is -- Would you want a proofing color
space to contain
the Pantone colors? Or to be limited to a subset of Pantone colors as many
real print
systems are?
I think you got the idea I was putting forth. My question is - is that
what you and Kai-Uwe
had in mind?
Best regards,
Ann McCarthy
Lexmark CPD
Imaging Systems Engineering
ICC Workflow WG Chair
Jan-Peter Homann <homann at colormanagement.de>
05/02/2006 01:41 PM
Please respond to homann
To: almccart at lexmark.com, OpenICC Liste <openicc at lists.freedesktop.org>
cc:
Subject: Re: [Openicc] new: Proof colour space
Hello Ann, and all,
Nice to hear, that leading ICC members are reading and posting to the
openICC list :-)
I think, your answer is two steps ahead, of the mail of Kai-Uwe.
As I understand him, he want the possibility of a free choosable
proofing colorspace independent from the RGB- or CMYK-workingspace in
ICC aware open source applications.
As I understand your concept of an "proofing colorspace" as an
intermediate colorspace between widegamut colorspaces like
camera-profiles on RAW data or AdobeRGB and printoutput.
Finetuning of colors and saturation is done in the "proofing
colorspace", if the work is done, gamutmapping from "proofing
colorspace" to print output colorspace needs and can be done either with
relatice colorinteric and blackpoint-comepnesation or with ICCv4
perceptual gamutmapping, if the gamut of the "proofing colorspace" is
similar of a better "reference medium gamut" for ICCv4 profiles.
Do I understand your intentions correct ?
:-) Jan-Peter
almccart at lexmark.com wrote:
>
> Hello Jan-Peter and all,
>
> So -- if we were to define a 'proofing colorspace' what would the
> requirements be?
> For example:
> 1. RGB encoding
> 2. Encompassing and similar in shape to the ISO printing gamut defined
> in ISO 12640-3 Annex B
> 3. Not significantly larger than the ISO printing gamut defined in ISO
> 12640-3 Annex B
> 4. Unambiguously defined transformations to/from CIE XYZ
> 5. Primaries placed so that if the file is incorrectly assumed to be
> sRGB, severe hue shifts do not occur.
> 6. Primaries placed so that HVS response to tone and hue adjustments are
> reasonably homogeneous
> throughout the space [i.e., perceptual isometry].
> 7. Adapted white point, color space white point and black point
> chromaticity = D50
> 8. Print-referred image state
> 9. Adapted white point and color space white point luminance: 160 cd/m^2
> [=ICC PCS]
> 10. Image surround - 20% of adapted white point
> ...?
>
> Does this represent a good initial list of attributes?
> Is there an existing public domain RGB that meets these criteria?
>
> Best regards,
> Ann McCarthy
> Lexmark CPD
> Imaging Systems Engineering
> ICC Workflow WG Chair
>
>
>
>
> *Jan-Peter Homann <homann at colormanagement.de>*
> Sent by: openicc-bounces at lists.freedesktop.org
>
> 05/02/2006 07:41 AM
> Please respond to homann
>
>
> To: Kai-Uwe Behrmann <ku.b at gmx.de>
> cc: OpenICC Liste <openicc at lists.freedesktop.org>
> Subject: Re: [Openicc] new: Proof colour space
>
>
>
>
> Hello list,
> A proofing colorspace would be very helpful.
> I know several photostudios, which are dealing with agencies, prepress
> bureaus and print shops.
>
> They are working in RGB and deliver RGB and CMYK-Files (ISOcoated) to
> their clients.
>
> Before they are converting to CMYK (ISOcoated) with relative
> colorimetric and blackpoint compensation, they do a proof and optimize
> the RGB-file, if colorclipping of saturated colors are occuring.
>
> The goal is to build an archive of RGB-files, where all RGB-files can be
> converted relative colorimetric with blackpoint compensation to the main
> destination colorspace, without the need to make image by image
> analysis , which rendering intent fits best.
>
> Most uzsers I know prefer to have a special menue for softproofing,
> instead of doing it in the colorsetting file.
>
> Very helpful is also, if the softproof menue is synchronized with the
> menue "convert to profile"
>
> If the softproof is OK, the file can be converted to the destination
> colorspace with one mouseclick.
>
> :-) Jan-Peter
>
>
> Kai-Uwe Behrmann wrote:
> > Hello list,
> >
> > what would you think about a dedicated proof colour space?
> >
> > The current situation in CinePaint is: we have RGB/Cmyk image data
> and can
> > proof them to whatever colour space on screen. If someone wants to
> > simulate an special output device like a film stock or a print media,
it
> > seems there is no sense by sticking to the editing colour spaces
> > (RGB/Cmyk). It is not clear if the user wants a RGB or Cmyk colour
space
> > to proof against.
> >
> > It could as well mean the proofing options should become a separate
> > advanced configuration group.
> >
> > Whats the opinion on the list about this matter?
> >
> > regards
> > Kai-Uwe Behrmann
> > + development for color management
> > + imaging / panoramas
> > + email: ku.b at gmx.de
> > + http://www.behrmann.name
--
--
homann colormanagement ------ 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 at colormanagement.de
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