The temp and tint sliders are directly related to
subtractive CMY colour theory.
Adjusting the temp slider gives you the obvious "more blue" or "more yellow" adjustment. This is also known as the "temperature" of the light, either cool (blue) or warm (yellow). Adjusting the tint slider gives you "more green" or "more magenta". In combination with the temp slider you can also do "more cyan" or "more red".
Between the two sliders you can account for any global colour cast in your image. If you only had temp available you could only account for blue/yellow cast. You couldn't deal with green, magenta, cyan, or red. All the "white balance" tool does is try to dial in a temp and tint value for you that will make your neutrals, uh, neutral. But you can season to taste or do it yourself by manipulating both sliders.
If you were in the colour film darkroom working with an enlarger head you'd be working with the exact same variables. Each enlarger head has a yellow and magenta filter pack, and to get rid of the colour cast in your print you'd dial in different amounts of yellow and magenta to address the issue.
I still have a
Kodak print viewing kit that you use when doing colour film prints to decide what adjustment to dial in. If you think your image is too cyan and needs more red you'd hold up the red test filter in front of your print to see the effect. Then you'd go into the darkroom, dial in the right amount of yellow and magenta, and do another print. Then you'd repeat many, many, times until it was right
Lightroom makes it a lot easier, but it's still the same concept. In fact, I still use my Kodak filters in front of the computer screen. It's pretty nice to sit back and say "hmm, I think this image is too cyan" and then hold the red filter up to see if I'm right!
Neil
