Hi, At 1 metre, the dof for the 50 is very shallow even with the aperture stopped down a lot, at 2 metres it is a bit more generous and you can get quite good at quickly adjusting the focus. With finger rest at the 6 o'clock position you are at 3 metres and have more leeway. The markings on the lens are optimistic even for film, for digital use the ones for at least one stop more open. But you will find that adjusting the focus is quite quick once you are used to the rf patch.
I do not have a 28, but with a 35 zone focusing is easier to use, still it is just as easy for focus as you shoot.
Jean-Michel