For enlarging lenses, in general the shorter the lens the higher the optimum magnification it is designed for. A 50 mm is probably best at 10x but the manufacturer's spec might say that it is good up to 20x.

We old-timers can remember a company called Nikon, who used to make quite decent enlarging lenses. Their 50 mm was best at 8x, but 'usable' from 2x to 20x. I never paid much attention to the 20x limit. The 40 mm f/4 EL Nikkor is better for high magnification though.

Best,
Helen