The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Samyang 20mm F1.8 and the Pentax D FA 24-70mm F2.8 ED SDM WR 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. Pentax D FA 24-70mm F2.8 ED SDM WR is the longer of the two lenses at 110mm. The Samyang 20mm F1.8 with a length of 88mm, is 22mm shorter. Besides being longer, the Pentax D FA 24-70mm F2.8 ED SDM WR also has a larger diameter of 89mm compared to the Samyang 20mm F1.8's 83mm 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. Samyang 20mm F1.8 weighs 497g, which means it is 290g (36%) lighter than the Pentax D FA 24-70mm F2.8 ED SDM WR which has a weight of 787g.
Lens Mounts
The Samyang 20mm F1.8 has the Pentax KAF lens mount whereas the Pentax D FA 24-70mm F2.8 ED SDM WR has the Pentax KAF3 lens mount. Some of the latest released cameras that are compatible with these mounts are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF Mount and Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF3 Mount.
Samyang 20mm F1.8 is also available in the Canon EF , Canon EF-M, Fujifilm X, Micro Four Thirds, Nikon F (FX), Samsung NX, Sony Alpha and Sony E mounts.
Focal Range
Samyang 20mm F1.8 is a prime lens with fixed focal lenght of 20mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
30mm.
On the other hand, the Pentax D FA 24-70mm F2.8 ED SDM WR has a focal range of 24-70mm and 2.9X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 36 - 105mm.
