20 mm, Fstop shot usually 4 or 5.6 so that I get all the people in the shot in focus. Here I'd like to learn to use a flash better to get the shutter speed down and keep the F stop high.
50mm, Fstop shot usually at 1.4. For true headshots, you actually need to go up to 1.8 otherwise ears are out of focus. Step back a foot and you are fine at 1.4 though.
85mm, Fstop I'd love would be 1.8....but damnit I want vibration reduction too because always shooting at shutter speeds of higher than 1/150th is really hard lightwise. I do hate having to use shutter speeds slower than 1/200th for any moving target, but when it is dark you have to start to compensate
200mm, fstop 2.8. Is really fine. Sure You could use a little more without ruining the picture, but I would surely spend dough making other ranges faster first.