Peter Nermander wrote: >> Yeh well thats not entirely logical either! You should be able to >>output to an industry standard and then tell the printer here's a >>job thats in industry standard format - use the printer specific >>profile built into the printer to output the job adjusted for the >>printer. > > The above statement makes me think you don't have the slightest idea > about the problems with color management. > > First of all we have the colorspace. The colorspace tells which > physical color (usually defined by CIELAB) a certain numerical value > (as for example the RGB value of a pixel in a JPEG pictore) > corresponds to. > > So for example a pixel with values RGB 12:34:56 is one color in sRGB, > but a completely different color in for example AdobeRGB. > > Now, CIELAB contains all colors visible by the human eye (as far as I > understand it), however other colorspaces contain only a subset. That > means that for example the colorspace AdobeRGB contains some colors > that CAN NOT be reproduced in the colorspace sRGB. The coverage of a > certain colorspaceis called gamut, colors that can not be reproduced > are "out of gamut" (and Scribus has support for showing you which > colors are out of gamut for the end device, if you have correct > profiles). > > Also RGB and CMYK are totally different. When you tell Scribus to > produce a PDF for print, it creates a CMYK PDF. But from what you are > writing (that your printer is using its built in profile) I think your > printer wants RGB data, so you should create a PDF intended for screen > (the only difference is RGB vs CMYK). > > This page doesn't cover everything, but is has links to further reading. > http://en.wikipedia.org/wiki/Color_management > > Color management is VERY complicated, and you have to make sure you > understand which profiles are needed for which translation. I know > enough about color management to understand that I shouldn't be using > it yet... I need to learn more.
Same here, but I suppose the frustration is that the documentation of most software doesn't make colour handling particularly clear. It would seem logical that if CIELAB is a colour space that can describe anything the human eye can perceive, that all images be stored internally in this format. This then requires a profile that describes the conversion of each input devices colour space to CIELAB, and another profile for each output space describing the conversion from CIELAB to the printer specific output. For PDFs which are frequently multi use things, it would presumably be sensible to keep images in the CIELAB format then use profiles for each VDU, CRT, LCD and mobile phone used to view them, or each windows or press printer that might be used to put them on paper. In the absence of such clear and well defined data flow, the mumblings about the complexity of CMS seem to contribute to a small of bad design. Is CMS something that needs to be complex, or just something that's got complex because of the lack of standard methods and clear description / specification ? In some ways it would be great to get into CMS and have everything come out as it should all the time, but for many, the pragmatic approach is to tweak curves a bit in gimp taking account of your experience with the target printer. I can't help thinking that CMS is an area that needs a good sort out, not so much in Scribus, but industry wide. Cheers, J/. -- John Beardmore, MSc EDM (Open), B.A. Chem (Oxon), CMIOSH, AIEMA, MEI Managing Director, T4 Sustainability Limited. http://www.T4sLtd.co.uk/ Energy Audit, Carbon Management, Design Advice, Sustainable Energy Consultancy and Installation, Carbon Trust Standard Registered Assessor Phone: 0845 4561332 Mobile: 07785 563116 Skype: t4sustainability
