Focal length only affects field of view, and not perspective. A picture taken from arm’s length will have the same amount of perspective distortion regardless of whether it is taken with a (35mm-equivalent) 24mm lens, 35mm lens, 50mm lens, etc. The only difference is how wide the field of view will be.
I see you address this in later posts, but @pixelshifter’s suggestion that it’s the wide-angle nature of smartphone cameras—and not the arm’s length perspective—that makes selfies look weird is wrong.[quote=“jerwin, post:12, topic:26947, full:true”]
This guy is a bit of an ass, but he presents images that demonstrate why it’s the focal length that matters, not the crop.
The guy’s an idiot. By his reckoning, an 85mm lens can’t be a portrait lens, either, because on MF an 80mm lens is normal and 35mm is just a cropped format relative to MF. And then your 150mm MF lens isn’t really a portrait lens, either, because it’s a wide angle on an 8x10 LF camera, and MF is just a crop of that format.
The only thing that matters is perspective, which is how far away you are from the camera. Pick your preferred portrait perspective (working distance). Then pick a focal length that gets you the framing you want. That’s your portrait lens for the format you’re using. It could be 5mm on a cell phone, or 600mm for an 8x10 view camera.