Basically, you can not adjust contrast as you do digitally with the levels tool. Ironically, you need the levels tool mostly because the digital systems suck and their designers have failed so that you need to fix the problems they have created.
When the contrast of R, G or B mismatch, it is called a "color crossover".
Actually, the negative films have very long straight lines with little crossover over a large range. Hence, just by adjusting R, G or B exposure, you can adjust the color balance quite a bit.
When you have to expose daylight-balanced film in tungsten light (which is not recommended, of course), the key point is to OVEREXPOSE. This is how you can avoid the blue going on the toe. OTOH, there is usually enough latitude before the red shoulders. If you overexpose 1,5 to 2 stops or so, you can correct the balance quite well in RA-4 printing.
"Tungsten" lights also vary quite a bit, from 2600 K to 3400 K. Photo lights and high-power halogens vary from 3000 to 3500 K whereas lowest-power general purpose bulbs can go as low as 2500 - 2600 K. Daylight film shot in 2600 K in practically uncorrectable, digitally or optically; whereas 3400 K is corrected easily either way.
Last edited by hrst; 06-12-2011 at 08:21 PM. Click to view previous post history.