Graeme Gill wrote: > As well, this is contradicted by the ICC spec. itself: > ICC V4.2 page 8: > > "The media-relative colorimetric transform is useful for colours > that have already been mapped to the intended reproduction > media-relative colorimetry, whereas the ICC-absolute colorimetric > transform is useful for spot colours, and when simulating one > medium on another in proofing applications." > > So what should one believe ?
If my understanding of what the ICC were saying, then the above only applies to print, at least currently. If they were simply trying to tell me that in order to support ICC-absolute colorimetry, the chad tag (or equivalent information) must be included in the monitor profile, then that wasn't at all clear to me. They explained that the chad tag would be required in order to do what I wanted to do, but they refrained from referring to this as "ICC-Absolute". They didn't even seem to understand why one would want to maintain the XYZ, viz: " If you really want the D50 white to be displayed why not set up your monitor to D50? You haven't answered that and I do need to know why that is a problem if I am to report it as I am sure that will be what will be said to me." Greg. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Graeme Gill Sent: Thursday, 21 July 2005 12:35 To: lcms-user@lists.sourceforge.net Subject: Re: [Lcms-user] XYZ values of colorants seem different? Greg Sullivan wrote: > Graeme wrote: >>If I try and reproduce spot colors on the display using >>ICCabsolute, hoping to be able to check for an exact match >>(as supposedly ICCabsolute is intended), then they won't >>match - the display output will be too blue. > > I thought that was the intent of ICCabsolute as well, but when I spoke > directly with a representative of the ICC about this some time ago, they > denied this, at least as far as displays are concerned. They explained that > in order to achieve what we want to achieve, we must determine the real > colorimetry first (using the chad tag, for example), and go from > there. But the ICC don't call this ICCabsolute. If this is in fact the case, then it's really asking for trouble. Most of those who have learnt something about color, have been taught that "Absolute Colorimetric is used for proofing and spot colors". As well, this is contradicted by the ICC spec. itself: ICC V4.2 page 8: "The media-relative colorimetric transform is useful for colours that have already been mapped to the intended reproduction media-relative colorimetry, whereas the ICC-absolute colorimetric transform is useful for spot colours, and when simulating one medium on another in proofing applications." So what should one believe ? > The reason for my own interest in this topic is that when I purchased the > Eye One Display product, and noticed that an absolute conversion from, say, > a D50 whitepoint to a D65 monitor produced a D65 result, I threw my arms > up in the air and exclaimed that Eye One Display was producing buggy > profiles. (as some of you will recall ;^) I think I ended up being satisfied > > that the Eye One Profiles aren't really buggy, although I wished that > they included the 'chad' tag. Right, they're not buggy, they're just ICC V4 :- incompatible with everything that came before ! :-) Graeme Gill. ------------------------------------------------------- SF.Net email is sponsored by: Discover Easy Linux Migration Strategies from IBM. Find simple to follow Roadmaps, straightforward articles, informative Webcasts and more! Get everything you need to get up to speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
