Here's a topic that just drives me crazy, because so many "experts" have no idea what it is and how it works. That's distortion. I'm at work and don't have any examples to post, but I can if anyone requests it. What so many writers and other so-called experts tend to refer to as "distortion", particularly regarding portraits, is actually just perspective, and not distortion at all. Distortion is an intrinsic characteristic of a lens. It's always there. You can obscure it or correct for it in post, but it is always there. When a lens takes a straight line and curves it, that's distortion. When you use a wide angle lens to get close to a subject, so that it's nose is a lot bigger than it's head, that's perspective, not distortion. This annoys me because I read so many lens reviews where people are taking portraits and talking about perspective and calling it "distortion" like it's some kind of mystery. I recently was reading a review of the Lensbaby Velvet 50mm lens, where this expert took a 3/4 length portrait and marveled at how it didn't have "distortion". That has nothing to do with the lens. It has everything to do with the camera to subject distance. On a full frame camera, a 50mm lens isn't desirable for a full face portrait, but it's fine for a 3/4 length portrait. Why? It has nothing to do with the lens and everything to do with the camera to subject distance. If you are shooting a full face portrait, you use a longer lens to move the camera further from the subject, which compresses the facial features. You could also use a 50mm lens, step back to the same spot where you would have taken the portrait with a 100mm and crop the image, and the result will be exactly the same, just at lower resolution. A 3/4 length portrait with a 50mm lens would be taken from even further from the subject than a full face with a 100mm. That's why it wouldn't produce exaggerated perspective. I got thinking about this because I'm planning to re-photograph all the teas at work for our web site. I want to do them in a completely different way, with tea spilling out of an amuse bouche spoon, and some exaggerated perspective to make it pop. I have this 15mm macro lens that will be perfect for it, but even shooting with a crop camera, the focal length will be shorter than I really want. Since the camera has far higher resolution than I need, I'm just going to put the camera on a macro rail to precisely adjust the camera to subject distance, and then crop the image to get exactly the perspective I want. By changing the camera to subject distance and then cropping the image, I am basically fine tuning the effective focal length to get exactly the result I want.