10 deviants said No, I know how to, but prefer using other tools (and will say which ones in the comments)
8 deviants said Yes, and I mostly just adjust luminance
6 deviants said I use real paint and/or a darkroom. Digital art is not for me.
5 deviants said What is this curves tool you speak of?
3 deviants said Yes, and I often adjust just the red, green, or blue channel