Hi, >to provide me with a simple method to check, wether our color-laserprinters >need to be profiled again, I created a graybalance strip. > ... > I have problems with patches below 20% which get too light,
The effect you see below 20% is normal, profiles does use CMY in addition of K to make darkest tones. Instead of going K->Lab->CMYK, you could use Lab->CMYK. That is, first create a ramp of, say, 25 levels of L* going from L*=100 to 0. Then, using rel. colorimetric and forcing a,b=0 convert this ramp to CMYK. Print resulting CMYK values. If the profile is valid, and has good gray balance, the result should be neutral or almost neutral, but keeping hue. Don't worry if the ramp is not so neutral, the eye is very sensitive to metamerism in this zone, The important part is hue should not change. If you see hue changes, you have to reprofile. The printed ramp should also appear "smooth", without abrupt changes, except in the very lowest part, which is the black point. L* will stop at the black point, which you can expect to be around L*=12 or more, but this hardly depends on media. As additional test, you can convert back these values to Lab using the proof direction of profile. It should result in values with a, b near zero, but this is not important, since it only checks whatever the profile has good proofing capabilities. Hope this helps. Marti Maria The little cms project http://www.littlecms.com ----- Original Message ----- From: "Christian Bednarek" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, August 18, 2004 4:52 PM Subject: [Lcms-user] graybalance check for provile validation Hello all, to provide me with a simple method to check, wether our color-laserprinters need to be profiled again, I created a graybalance strip (http://eazy.amigager.de/~eazy/icc/proofBar.ps). This strip is created by transforming black values like CMYK(0,0,0,K) with 15<=K<=75 into lab and back to the current cmyk profile of the printer. This strip is created along with every new profile I create. I have problems with patches below 20% which get too light, but this seems to be a problem with the profile, not with lcms. The ICC-engine in front of the printers (jaws) does create the same light results, so Profilemaker 4.1 might be the bad one here (or me, with choosing wrong options for profilecreation ;). My question: is this a good way or are there better ways to validate a profile? -- Gruss, Christian Bednarek ------------------------------------------------------- SF.Net email is sponsored by Shop4tech.com-Lowest price on Blank Media 100pk Sonic DVD-R 4x for only $29 -100pk Sonic DVD+R for only $33 Save 50% off Retail on Ink & Toner - Free Shipping and Free Gift. http://www.shop4tech.com/z/Inkjet_Cartridges/9_108_r285 _______________________________________________ Lcms-user mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/lcms-user ------------------------------------------------------- SF.Net email is sponsored by Shop4tech.com-Lowest price on Blank Media 100pk Sonic DVD-R 4x for only $29 -100pk Sonic DVD+R for only $33 Save 50% off Retail on Ink & Toner - Free Shipping and Free Gift. http://www.shop4tech.com/z/Inkjet_Cartridges/9_108_r285 _______________________________________________ Lcms-user mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/lcms-user
