The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron 20-40mm F2.8 VXD and the Samyang 8mm 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. Tamron 20-40mm F2.8 VXD is the longer of the two lenses at 86mm. The Samyang 8mm F3.5 Fisheye with a length of 77mm, is 9mm shorter. On the other hand, the Samyang 8mm F3.5 Fisheye has a larger diameter of 75mm compared to the Tamron 20-40mm F2.8 VXD's 74mm 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. Tamron 20-40mm F2.8 VXD weighs 365g, which means it is 78g (17%) lighter than the Samyang 8mm F3.5 Fisheye which has a weight of 443g.
Lens Mounts
The Tamron 20-40mm F2.8 VXD has the Sony E lens mount whereas the Samyang 8mm F3.5 Fisheye has the Pentax KAF lens mount. Some of the latest released cameras that are compatible with these mounts are Sony FX5, Sony A7R VI and Sony A7 V for the Sony E Mount and Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF Mount.
Samyang 8mm F3.5 Fisheye is also available in Canon EF , Nikon F (DX), Four Thirds, Sony Alpha and Samsung NX mounts.
Focal Range
Tamron 20-40mm F2.8 VXD has a focal range of 20-40mm and
2.0X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
30 - 60mm.
On the other hand, the Samyang 8mm F3.5 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.
