I'd wanted a fisheye lens since I was 15 years old, reading the Spiratone ads in the back of magazines. A couple summers ago I bid $200 on a used Sigma 4.5mm 180 deg. circular fisheye lens. And I won. Oops.
It was crazy hard to use. I had to pay attention to my feet and belly. Had to develop a fisheye stance. The whole notion of crazy lines is what you'd expect, but there's so much real estate to keep track of. And no cropping available.
I think I took it out 3 times before I decided that it wouldn't take long to get a reputation as the 'fisheye guy.' I couldn't have that, so I sold it. But that lens taught me a lot about ultrawide photography. I still find 16mm hard to wrangle, but I'm better at it for having fought with the 4.5.
Barrel Distortion
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The day the lens came in the mail, I chucked it on a body and took it out in the backyard to look through it. I shot this ladder straight on leaned against the house in a corner with a chimeny. At the time, just something to look at. When I got it in post, I found a carpenter's square for a 180 deg. circular fisheye. Shows what all the lines do. Showed me what to expect in the field.
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