Marti, Thanks again. I'm sorry to waste your time. :) Do I have your permission to post this reply to newsgroup comp.periphs.scanners, thread "LS-4000 weak gamut?" ? Alternatively, you could post it yourself, or I could just post a summary etc. Let me know.
Regards, Greg. (feeling a lot better about my scanner now! :) -----Original Message----- From: Mart� Maria [mailto:[EMAIL PROTECTED]] Sent: Thursday, 23 January 2003 1:47 AM To: Sullivan, Gregory (SNL); [EMAIL PROTECTED] Subject: Re: [Lcms-user] How good is the Profiler for slide film? MessageHi, > Thanks for the feedback. I'm glad the profile looks basically ok. But I don't > understand why the gamut is so enormous. If you superimpose even the sRGB > trangle over my scanner profile, there is more green gamut in sRGB. And sRGB >is considered a rather small gamut. Is it the case that slide film doesn't have a very > large green gamut? Don't trust too much the primaries triangle. Gamut hulls are 3 dimension solids, so the projection on a 2D plane sometimes is not as meaningful as it should. Also, as said, the profile is not using these primaries. Is just a information stored into the profile, mostly for detecting coarse errors. The profile really works using a tridimensional lookup table, which has no primaries. And for the gamut extent, I will try to do a quick demostration on how big it is. There is a utility called "icctrans", that could be used to evaluate numbers across profiles. For example, I will first check sRGB, getting the Lab of sRGB=(10, 200, 10). I'm using sRGB profile as input and the Lab built-in as output. H:\lcms>icctrans -i"sRGB color Space profile.icm" -o*Lab little cms ColorSpace conversion calculator - v1.4 Enter values, 'q' to quit R (255)? 10 G (255)? 200 B (255)? 10 L*=70.5162 a*=-65.4727 b*=66.5039 That is, in sRGB a pixel with values (10, 200, 10) represents a color with Lab = (70.5, -65, 66) This is a moderate saturated green. Let's now check your profile: H:\lcms>icctrans -ils40_provia_astia_g22.icc -o*Lab little cms ColorSpace conversion calculator - v1.4 Enter values, 'q' to quit R (255)? 10 G (255)? 200 B (255)? 10 L*=74.1437 a*=-99.7109 b*=116.1289 Ouch! same device value gives a Lab of incredible saturation Lab= (74, -100, 116)!!!! This is fair out sRGB gamut. That means your scanner can capture greens as saturated as having ab of (74, -100) and still have levels 200 to 255 for more... A really huge gamut indeed ;-) Regards, Mart� Maria The little cms project http://www.littlecms.com [EMAIL PROTECTED] ----- Original Message ----- From: Sullivan, Gregory (SNL) To: [EMAIL PROTECTED] Sent: Wednesday, January 22, 2003 12:51 PM Subject: RE: [Lcms-user] How good is the Profiler for slide film? Marti, Thanks for the feedback. I'm glad the profile looks basically ok. But I don't understand why the gamut is so enormous. If you superimpose even the sRGB trangle over my scanner profile, there is more green gamut in sRGB. And sRGB is considered a rather small gamut. Is it the case that slide film doesn't have a very large green gamut? I haven't tried the improved profile you sent me yet, but thanks for building it. Regards, Greg. p.s Still can't get over the fact that this software is freeware!! J ------------------------------------------------------- This SF.net email is sponsored by: Scholarships for Techies! Can't afford IT training? All 2003 ictp students receive scholarships. Get hands-on training in Microsoft, Cisco, Sun, Linux/UNIX, and more. www.ictp.com/training/sourceforge.asp _______________________________________________ Lcms-user mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/lcms-user
