Small review of the Peleng 8mm f/3.5 fisheye:
Mechanical quality:
This is an all metal lens of decent mechanical quality. It feels very solid. There is a tiny amount of slop in the mount that isn't more than frequently can be experienced with any legacy lens. The OM-mount is a bit coarse in the fit to the OM-->Fourthirds adapter. The rear lens does NOT protrude at all beyond the OM-->4/3 adapter (as some sources on the web claims). The lens cover is sturdy metal and protects the domed objective lens. However, it is a bit loose and I recommend the velvet friction strip to be replaced ASAP.
Optical quality:
The lens gives almost a full frame fisheye with a >165° diagonal angle of view. The Fourthirds sensor is small enough to not include the outer rim in the image circle which significantly improves the captured image quality (compared to larger sensors).
I found that the lens is soft at f/3.5 but already at f/5.6 it becomes quite sharp. The image quality across the picture at f/5.6 is pretty OK in the center but notably soft at the edge.
The lens coating isn't perfectly uniform but I haven't seen any negative effects of that.
Shooting against the sun may/may not give severe lens flare depending on the exact angle towards the sun. I have made myself a petal hood that helps alot.
Usefulness:
To summarize: Not many amateurs will use such a lens extensively but the fact that it cost about 1/8:th of the Zuiko Digital 7-14mm zoom (or 1/4 the price of the Zuiko Digital 8mm fisheye) makes it actually quite a sensible lens to have. The lens is certainly not as good as a high-end lens but for 'creative' photography, it serves its purpose very well. For the price ($225 includuding S&H), I find it still extremely good value, and for many types of shots like snowboarding, skateboarding, etc. it will give me a lot of fun.
See my longer review with sample images here
Cheers, Jens.
NOTE: There is a serious problem with the OM-adapter that influences the focus with this short focal length. The OM-adapter is 0.1 mm thinner than the ideal thickness required to produce the infinity focus setting of an OM-lens at the actual infinity mark. With lenses of 'ordinary' focal lengths where the lens package moves several millimeters, that is not critically important. However with an 8 mm lens, the lens package moves only about 0.1 mm when focussing from 0.3 meters to infinity, hence making it impossible to trust the focus scale. This severely limits the very convenient shooting style to set the hyperfocal distance on the distance scale and rely on the immense DOF of the lens.