a better way to get accurate L* from an ICC profile.
1. Open the ICC file using Profile Inspector
2. Double click the "A2B1" tag
3. Choose CLUT tab
4. Make sure all channels on 0
5. First value on the right-up side is L*min (16 bit)
Thanks, I was very interested to read about this. Note that you don't have to divide by 65535 and multiply by 100 to get a 0-100 scale. In the right pane, under Values, to the right of the top box, it shows you the L* value on a 0-100 scale, rounded to the nearest 1.
Exploring using this method, I decided to inspect some of my own ColorMunki-made profiles, and compare the data there to my observations made using ICC View 3D gamut plots, where I'd previously estimated that my visual readings were precise within +/- 1 or 2.
Canson Rag Photographique 210 - 11, versus 10 observed
Canson Arches 88 - 13, same as observed
Epson Legacy Baryta - 10, same as observed
Epson Legacy Etching - 19, versus 14 observed
Epson Legacy Fibre - 12, versus 10 observed
Epson Premium SemiGloss - 3, versus 2 observed
Epson Ultra Premium Glossy - 4, versus 2 observed
Hahnemühle Photo Gloss Baryta - 8, versus 7 observed
Hahnemühle Photo Rag Pearl - 4, versus 2 observed
Red River Palo Duro Softgloss Rag - 6, versus 5 observed
Red River Pecos River gloss - 7 , versus 5 observed
Obviously 6 of the 11 are either the same or off by 1, and 4 are off by 2; but one is off by 5! I rechecked Epson Legacy Etching, the visual implication of L* min = 14 is clear (shown below), while Profile Inspector, using the method above, clearly shows it = 19. Also, that my observed values were often lower but never higher suggests to me that a parallax-type error may significantly affect the visual inspection.
At this point, a question: my observed L* min values stated above are all absolute minimums, not minimum at a* = 0, b* = 0. Is there some rule or convention that when reporting L* min, by default that means at a* = 0, b* = 0, even if a lower L* is achievable at a non-neutral color? With my little Epson, the absolute L* minimums are all fairly close to a = 0, but the b values appear to be between -4 and -9, i.e., apparently the 'black' ink prints somewhat blue.
Also, there's an apparent oddity: in the A2B1 CLUT tab, when you drag the Ch0, Ch1, and Ch2 sliders from 0 to maximum, every single profile shows 65280, which corresponds to L* max = 99.6, which is certainly not the white point of all these papers. If it were 65535, then I'd say, 'Well, this is something else, it doesn't tell us L* max.' But 65280?
My learning and exploration continues--and any and all of your comments and suggestions are much appreciated.