So I understand how a single curve works:
If you create a curve such that R100 (in) becomes R50 (out), every pixel that has an R value of R100 becomes R50.
Similar deal with the RGB curve:
if you set RGB100 -> RGB50 any pixel that has R or G or B of 100 becomes 50.
So my question is, I've set a RGB curve such that RGB100 -> RGB50 and R100 -> R125, the result is all R100 -> R73. If I reverse that so RGB100 -> RGB125 and R100 -> R50, the result is all R100 -> R66. If I set both RGB100 -> RGB50 and R100 -> R50, the result is all R100 -> R19...
What is the interaction there (mathematically) between the RGB curve and R curve? This is all on the same curves layer.