LAB color, 2 sample chapters

[Larry Marso]

The following site *legitimately with permission from the author* has
two chapters online of Dan Margulis' exciting book "Photoshop LAB
Color".  (I do not know Dan or his publisher and for goodness sake I'm
NOT promoting the book).

http://www.ledet.com/margulis/articles.html

Page 2 of the "Chapter 9" sample depicts color curves under LAB in
Photoshop.  You will note that they are "inverted" in that they go
from light at the lower left hand corner to dark at the upper left. 
The L channel is luminosity, A rebalances Green and Magenta, and B
rebalances Blue and Yellow.  Page 12 has another example of common
manipulations to LAB curves.

Page 10 shows the fascinating color channel layer blending tool in
Photoshop.  You can pick a color channel, then selectively decide
where along the gamut you want color blended with the layers below,
including the ability to decide upon a fading range rather than a
fixed endpoint.  (This particular widget is probably off in the
future, as it is an adjustment layer, and as I understand it, Krita
developers are struggling with the basic layer model).

The "before and after" of a downtown alongside waterfront on Page 16
shows the use of these two tools together, to modify an image and
selectively blend down the result.

Unfortunately, these samples do not include any images or examples of
the color channel value averaging tool based on a defined radius.