A few weeks back I was able to test out the Bower 8mm fisheye lens designed with the APS sensor in mind.
The model I tried was labeled Bower, though there are many other names on the same lens produced by Samyang/Rokinon.
Supposedly an all manual lens I found the Pentax version functioned in both A & ATV priority as well.
The exposure settings on the lens seemed to be true to my camera, about 1/3 less needed in post. I only tried f5.6 & 8, as most reviews I’d read mentioned sharpness dropping off after f11.
The Bower 8mm fisheye lens instructions suggest focusing in live view. I didn’t find this helpful and found the focusing ring the best option. Other reviews mention having to calibrate the focusing ring to infinity for the model/brand camera you own. I found this to be the correct. At 1.5 feet it seemed accurate but noticed the ring would go past infinity on the scale and would be a bit out of focus.
The price is about 2/3’s less than the Pentax 10-17mm I rented a few years back and I would say the image quality of the Bower is as good. Also, I think there is less distortion than with the Pentax.
If you find yourself needing a fisheye for a project, I would consider renting a Bower 8mm fisheye/wide-angle lens. For the price they seem to be a quality lens.
More images taken with the Bower 8mm fisheye lens may be seen in archives/ghosttowns.