2002.03.05 20:31 "Re: 16 bit LAB in TIFF - documentation update", by Chris Cox
- A lot of experimentation did show me that Adobe is using D50 as white point. This clashes with the D65 required by old spec. Which white point is supposed to be used?
We already document that Photoshop LAB is D50 based (since version 5.0 - before that it was white point neutral....).
Technically, any whitepoint CAN be used. We recommend D50, but leave it open because some third parties want to use D65.
As Martin Bailey noted, perhaps the whitepoint tag should be made optional for LAB data.
- About ICCencoding. Lately, ICC has released spec 4.0, with several major changes. One of them that PCS L is no longer encoded as 0...ff00 but 0..ffff I'm amazed by the side effects this would have in, for example, TIFF Lab. The note talks about ICCLab with encoding 0..65280 But in current ICC spec PCS is encoded as 0..65535.
Ok, perhaps I need to specify the version of the ICC spec. (this update was started before the version 4 spec. was complete -- but the mutually incompatible encodings held things up for a while)