I adore being able to shift, offset, or translate ab in Lab. The commons tools for this seem to be Levels and Curves. Same thing possible with other tools, but I have yet to hear anybody talk about them.
But the thing that sucks about Levels/Curves is the drop-down. I know it's a minor thing, but it really gets on my nerves. I would much rather have the controls right there in one shot. Believe it or not, but Hue/Sat can be hacked to adjust ab colour balance with a bit of savy, and you will have the controls right there instead of having to switch channel controls.
- photograph that needs some general balancing
- Image > Mode > Lab
- New Layer and fill with L=50%, a=30, and b=30 (your colour palette is in Lab mode, right?)
- set Blending mode to Linear Light
- Advanced Blending
-- turn off L channel
Right about now you should be looking at a mess. Now for the fun part.
- Adjustment Layer > Hue/Sat and clip it to the Linear Light layer
- Open up the Hue/Sat dialog and get crazy with the Cheez Whiz
What you are basically doing is offsetting a and b in a particular direction. You use the Hue slider to set the direction, and use the Sat slider to set the amount. Seems to do decent enough with a little practice.
Should get you thinking about different ways of manipulating ab. Again, not without irony of some sort. Using a polar system to offset a Cartesian system. Man, that cracks me up.
