The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Venus 4mm F2.8 FMFT and the Rokinon 7.5mm f3.5 Fisheye 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 Venus 4mm F2.8 FMFT with a length of 26mm, is 22mm shorter. On the other hand, the Venus 4mm F2.8 FMFT has a larger diameter of 61mm compared to the Rokinon 7.5mm f3.5 Fisheye's 60mm 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. Venus 4mm F2.8 FMFT weighs 135g, which means it is 62g (31%) lighter than the Rokinon 7.5mm f3.5 Fisheye which has a 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 Venus 4mm F2.8 FMFT and the Rokinon 7.5mm f3.5 Fisheye 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-3 Astro, OM System OM-5 II and OM System OM-3.
Focal Range
Venus 4mm F2.8 FMFT is a prime lens with fixed focal lenght of 4mm which has an effective (full-frame 35mm equivalent) focal range of
8mm when used on a FourThirds format camera.
On the other hand, the 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.
