Hey Greg,
You got me on a better track.
When using LAB (still feel it is great to fix WB issues, and my idea to move the center points according to marker values can be a great assist, if not a very good to perfect way to deal with the issue) One has to be sure to choose the correct points of correspondence. As you did point to me. Thnx!!! A big help is do look during the process very well to what the light is doing in the picture. Be aware of false assuptions (as i did first by thinking the walls should be white. You are right they are not! As you said the color differences are very subtile. I have values though miss your color clock. To bad the clock made by Chris also does not work on linux. :-(
The couch and the walls. To my current findings it has some slight greens and some slight yellows in it.
So i did do it over again working with three reference points.
1 Did start with cover on the stove
2 A point at hard point on the ceeling where also the red cast can occur.
3 A point a the grass in the picture on the wall above the stove
I think i am very close now. There one color in the image that does bother me now. And that is the brown in the floor. If i look at that it tells me i am close but not really quite.
I tells me i went to hard on the reds, (prolly correcting the sealing) ?
See:
We did pick a hard image to get real good. Though those are the once one gets better by.
For me i rather start in LAB and go to CMYK for the final touch. When one needs to be real subtile Luminance blending CMY channels seems to me then just great. (or if one does like RGB in RGB, though i am no RGB dude) That man from mars methode that other guy (http://livestre.am/DSAO) did show, does blow my mind off. He sure is on track there imo.
Though some how his way does not work in the program i use :(
It is atm still very beta, though if you want to check it. a windows version is here. http://code.google.com/p/delaboratory/downloads/list (export option does not work there, fixed in svn) As said i use linux svn version .
Post script:
I did check on the value's have now on the shadows on the portraits on the stover cover. (how is that one called in proper English ;-)
those should have imo a close to natural grey?
I know the guy who did make the shoot somehow, i could ask him about the wall colors as we only have educated guesses. You feel it dif, though i think i even still have a green cast. (color overlay that not should be there and covers other colors)
Btw on LAB beeing a hammer, I do not know or CM does have a curve fine control by f.i keyboard control. Aka for the very small moves on a curve a kinda micro adjustment?
I did try software that has Ctrl + mouse wheel for per pixel up or down and Shift + mouse wheel for per pixel left and right. It does not support layers and values. :-( So they have a great micro adjust though one still walks blind fouled.
Btw i have a European background. so it might i just look diff couse of that.
That is also why i like this methode, it goes by values and light. all is free from there.