I earlier posted experiments with the old Samigon 180-Degree Fisheye auxiliary lens I picked up earlier in the spring. It's designed to give a circular fisheye image when used with a main lens of the "normal" focal length for the format being used. You set that focal length on the Samigon, set the main lens to infinity and its widest aperture, and then stop down the Samigon 2 stops from it's widest aperture available (the range of stops is different depending on what main lens focal length is set). I've found that I get better sharpness stopping down about 3 stops, or just setting the Samigon to its middle aperture setting.
Using the Samigon FE with a 50mm prime on either my K110D or K10D, as can be seen in my earlier posts results in an oval image, since the 50 isn't really a normal lens for the frame size of the ASP-C sensor. So far I haven't succeeded in getting a circular image, tangent or nearly tangent to the frame, on these dslrs. But I'm also interested in finding out how to get a good rectangular image, without corner vignetting, from the Samigon FE. Earlier I tried pairing it with a 135mm prime, and that worked, but it also seemed to reduce too much of the FE effect. Yesterday, I tried pairing it with 100mm (using a 50mm + a 2x TC), and that worked better. Then I tried pairing it with 75mm (using a 50mm + a 1.5x TC); I was expecting to get vignetting that time but I did not!
I like the horizon bending background.
Part of the FE fun is combining near and far. The front of the lens combo is about 2 inches from the thistle blossom.
Did I only shoot verticals? No, but these were more interesting test shots than the horizontals I shot. I'm getting a 35mm prime to see if that will give me a large circular FE image on the cropped digital sensor. I tried a 28, and it makes the circle too small.