I've finished reviewing the Canon EF 8-15mm f/4L Fisheye USM lens, and I must say that the performance is pretty impressive!
Works really well for some interiors
Incredible sharpness for a fisheye lens, and solid flare resistance!
The Canon EF 8-15mm f/4L Fisheye USM is not a lens for everyone, given its relatively high price tag and exotic focal lengths. However, it does feature superlative optics for a fisheye lens, so you do get very good results even at the extreme angles, which is quite a feat of optical engineering. The lens may seem bulkier and heavier than its predecessor (EF 15mm f/2.8), but given that it incorporates both a circular and full frame fisheye, it is actually two lenses in one and quite worth the premium in weight and size.
I started the review with the distinct feeling that I will be shooting more full-frame fisheye shots, but ended up with quite a lot of circular fisheye shots instead! I thought that the occasions for using a circular fisheye lens are very limited, but that turned out to be a misconception. It is more difficult to plan for a circular fisheye shot, but it is merely an additional step to retrain your eye. In many cases, the full frame is sufficient to capture the elements. In some cases though, having the circular fisheye option makes all the difference in the world.
The optical performance of the Canon EF 8-15mm f/4L Fisheye USM is very good for a fisheye lens, especially at the 15mm end for full-frame fisheye images. There is excellent resolution for fine details, and tight control of contrast and flare suppression. Chromatic aberration is virtually non-existent, which is an impressive effort on the part of the optical engineers.
You can read more about the Canon EF 8-15mm f/4L Fisheye USM review here!