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thanks for your answers. Dan, I think you are right concerning the word “teal” for people whose first language isn’t english. As a non native speaker, I had to consult an online dictionary for the meaning of teal.

Concerning this red vs. magenta thoughts, I made my own chart. You can download it here, if you are interested : http://giebel-foto.de/download/Lab-rot-Diagramm.jpg
It shows a-values from 0 to max (x-axis) in steps of L by increasing 10 each (y-axis). You can find hues that I would suggest as red, but the great majority is clearly magenta. Thanks for the discussion folks.

Best Regards from germany,
Martin

Up until the turn of the century *everyone* referred to the A channel as red-green; I did so myself in the first two editions of Professional Photoshop (1993 and 1997).

By the end of the century I was spending more time studying LAB and I realized that “red-green” was inaccurate. I was the first to call it “magenta-green”, in Professional Photoshop Third Edition (aka Professional Photoshop 6) in 2000. Today we still find sources that have picked up the obsolete “red-green” but anybody who’s serious about working in LAB now won’t use that term.

I thought hard about calling it magenta-teal rather than magenta-green, because a value of A-negative B-zero is much too blue for vegetation, yet not blue enough to warrant calling the color cyan. But anyone expecting that the leaves of trees would be this color might have a nasty surprise.

I decided to just stick with “green” because “teal”, although fairly accurate, may not be familiar to everyone, particularly those whose first language is not English. “Magenta”, meanwhile, is a word that everyone understands, and everyone who looks at LAB understands that an A-positive B-zero value is magenta, not red.

thanks for sharing this great LAB grid. Do you know why the positive “a” values are nearly everywhere mentioned as red (and not magenta)? I found that very misleading in other publications. As far as I have read about LAB, you are the only author who refers positive a as magenta and not red.

Best Regards,
Martin

However, I have a other doubt. In the text p.64 is described “Assuring color fidelity in objects that are about deleted, such as gray card, is a low priority. Assuming you agree that exaggerated colors of Figure 3.21B are superior to those of 3.21A, you have just decided that an inaccurate gray card is acceptable.”
I think that the ideia not stayed clear. It would not be ” Assuring color fidelity in objects that are about to be deleted, such as a gray card is a low priority. Assuming you agree that the exaggerated colors of Figure 3.21B are better than 3.21A, what we realize is that even an inaccurate assessment of gray is acceptable to the fix the color balance. The original idea is not to despise the evaluation of the gray card and seek a review by the internal evidence of the image?
Forgive me if I seem boring, but understand the idea for me is very important, without fully understanding the concept the reading is becoming increasingly difficult.