Hi Glenn, > I have a large format printer printing 6 colours. The RIP is using a 6 > colour output profile and assumes Adobe1998 as the input RGB profile for > RGB colours. However I dont have the ability to create 6 colour profiles > so to get better matches I have created RGB profiles for specefic media > through the RIP using relative colourimetric rendering intents. (Print > RGB charts and create a profile)
Humm... The targets are RGB? How do you print the targets? Do you print the targets using normal workflow? In such case you would be profiling the AdobeRGB path, which is not necessary a bad idea. > This however requires that I convert any file to print to the specefic > Printer RGB profile in Photoshop, Do you mean the RGB profiles you created on top of the AdobeRGB path? > However I do get very good results > turning on Black Point compensation. For example the workflow for an > Adobe1998 image is Adobe1998 > RCM+BPC > PrinterRGB > [RIP assumes > Adobe1998 > RCM > Device 6 Colour ] Ok, I see, you basically are profiling the AdobeRGB path. Well, as said this is not a bad idea, because some printers (HP DesignJet, for example) does a special "perceptual" mapping for sRGB and aRGB paths. This mapping is close to colorimetric inside printer's gamut but colors are moved "perceptually" in gamut boundaries. Profiling that path gives you more colorimetric accuracy, but undoes the nice gamut mapping the colormap has. > Using this procecess I see the deltaE improve from around 4-5 to 1-2 for > in gamut colours. That's a big improvement. At that point I would also check the plot-to-plot repeatibility, just to make sure those 1-2 dE are stable. Most vendors have to face printer-to printer repeteability, so 4-5 maybe are not such bad for a generic printer. > What I could like to do is to use the PrinterRGB profile to UPDATE the > A2B table of the 6 colour ICC profile. In effect making it more accurate > [...] You may use icclink to do the trick. Please note the obtained profile would be a crafted output profile with just one intent and no proofing capabilities. icclink -x -t1 -b -o aRGBto6.icc *Lab PrinterRGB.icc AdobeRGB1998.icc 6inks.icc You would need to use a different PrinterRGB.icc for each media, and the gamut is limited to AdobeRGB (I guess this is not an issue). Otherwise it should work. Regards Marti ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
