The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Rokinon 7.5mm f3.5 Fisheye and the Olympus 9mm F8 Fish-Eye for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is a crucial factor to consider when comparing two lenses. Rokinon 7.5mm f3.5 Fisheye is the longer of the two lenses at 48mm. The Olympus 9mm F8 Fish-Eye with a length of 13mm, is 35mm shorter. Besides being longer, the Rokinon 7.5mm f3.5 Fisheye also has a larger diameter of 60mm compared to the Olympus 9mm F8 Fish-Eye 's 56mm diameter.
The weight of a lens is equally significant as its external dimensions, particularly if you intend to handhold your camera and lens combination for extended periods. Olympus 9mm F8 Fish-Eye weighs 30g, 84% (167g) lighter than the Rokinon 7.5mm f3.5 Fisheye's weight of 197g.
Below you can find the dimension and weight table of the Wideangle Fisheye Prime Lenses in Micro Four Thirds Mount for size comparison purposes.
Ultra-Wideangle Lenses in Micro Four Thirds Mount for Size Comparison
Lens Mounts
Both the Rokinon 7.5mm f3.5 Fisheye and the Olympus 9mm F8 Fish-Eye has the same Micro Four Thirds lens mount. Some of the latest released cameras that are compatible with the Micro Four Thirds lenses are OM System OM-1 II, Panasonic G9 II and OM System OM-5.
Focal Range
Rokinon 7.5mm f3.5 Fisheye is a prime lens with fixed focal lenght of 8mm which has an effective (full-frame 35mm equivalent) focal range of
16mm when used on a FourThirds format camera.
On the other hand, the Olympus 9mm F8 Fish-Eye is a prime lens with fixed focal lenght of 9mm which has an effective (full-frame 35mm equivalent) focal range of 18mm when used on a FourThirds format camera.