I think the limiting factor is space between the lens and photo paper.
And it depends on what size prints you might make. A 50mm will work fine on half-frame -- and you'll only be using the central part of the enlargers glass which is usually the sharpest. But if you want to make larger prints, like me, you can easily run out of enlarger column -- depending on the enlarger, of course. A 50mm gives you much more space between the lens and the paper which can be nice when making smaller prints. There are pros and cons. Since enlarging lenses are so inexpensive, I use a 28mm f4.


