The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Samyang 8mm F2.8 Fisheye and the Canon 75-300mm f4.0-5.6 III for their suitability to various photography scenarios:
Size and Weight Comparison
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. Samyang 8mm F2.8 Fisheye weighs 265g, which means it is 215g (44%) lighter than the Canon 75-300mm f4.0-5.6 III which has a weight of 480g.
Lens Mounts
The Samyang 8mm F2.8 Fisheye has the Samsung NX lens mount whereas the Canon 75-300mm f4.0-5.6 III has the Canon EF lens mount. Some of the latest released cameras that are compatible with these mounts are Samsung NX1, Samsung NX3000 and Samsung NX30 for the Samsung NX Mount and Blackmagic URSA 12K LF, Z CAM E2-F6 II 6K and Z CAM E2-S6 II 6K for the Canon EF Mount.
Samyang 8mm F2.8 Fisheye is also available in the Sony E mount.
Focal Range
Samyang 8mm F2.8 Fisheye is a prime lens with fixed focal lenght of 8mm which has an effective (full-frame 35mm equivalent) focal range of
12mm when used on a APS-C / DX format camera.
On the other hand, the Canon 75-300mm f4.0-5.6 III has a focal range of 75-300mm and 4.0X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 120 - 480mm.
