I'm new to film. My first film camera 6 months ago is my RB67. My first LF is a Speed Graphic.

If I wanted to shoot a long exposure lets say of a stream or something along those lines, how do I make sure I don't have reciprocity failure, short of shooting B/W.

When I mentioned that I was thinking of shooting some longer exposed work, one photographer mentioned "reciprocity failure".

How is that avoided, or does it really come into play for LONG exposures such as 15 minutes and so on, and even then how are those folks shooting lets say stars at night, and not getting reciprocity failure?

Is reciprocity failure just applied to color film?

TIA