Originally posted by UncleVanya I disagree in practice despite the theory saying you are right. I have many shots that don't fit that model but work well. Post some shots with APSC 50 and longer and illustrate your concerts.
Ok this is going to be hard to prove from my own work, but I will give it a try imperfect as the comparison is going to be. All shots are of my friend Jesse. Comparison is with the Canon FL 55mm 1.2 which is generally agreed to be a good portrait lens on full frame and the FA77 which everyone agrees is a good portrait lens on APS-C or full frame.
First shot K5iis Canon FL 55mm 1.2 I am guessing this is either 1.2 or 1.4 simply because the ISO is 100 and the shutter speed is 1/40 indoors with some natural light and overhead illumination.
I like the photo well enough, but the facial lines are stronger than what I'd like in a portrait.
Second shot K5iis FA77 f2.5 ISO 100 1/125 mostly diffused natural light with some overhead. Even closed down more than the Canon, the facial lines are less pronounced.
Third from a headscarf series I did with near ideal natural light. FA77 f2.8 ISO 100 1/100
This of course proves nothing. I even like the first photo although Jesse did not because it highlighted facial lines. But objectively, the longer lens, even stopped down a bit, gives a more classic portrait look. If you are going for character and grit, then its true that a the shorter focal length will work fine and may even be preferable. But that's not typically why someone buys a portrait lens, which was the OP's goal.