The type of photography that you are planning to use is an important decision factor. Here we have evaluated the HD Pentax-DA 10-17mm F3.5-4.5 ED fisheye and the Voigtlander 20mm F3.5 SL II 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. HD Pentax-DA 10-17mm F3.5-4.5 ED fisheye is the longer of the two lenses at 70mm. The Voigtlander 20mm F3.5 SL II with a length of 29mm, is 41mm shorter. Besides being longer, the HD Pentax-DA 10-17mm F3.5-4.5 ED fisheye also has a larger diameter of 68mm compared to the Voigtlander 20mm F3.5 SL II's 63mm 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. Voigtlander 20mm F3.5 SL II weighs 205g, 35% (112g) lighter than the HD Pentax-DA 10-17mm F3.5-4.5 ED fisheye's weight of 317g.
Lens Mounts
Both the HD Pentax-DA 10-17mm F3.5-4.5 ED fisheye and the Voigtlander 20mm F3.5 SL II has the same Pentax KAF lens mount. Some of the latest released cameras that are compatible with the Pentax KAF lenses are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III.
Voigtlander 20mm F3.5 SL II is also available in Canon EF and Nikon F (FX) mounts.
Focal Range
HD Pentax-DA 10-17mm F3.5-4.5 ED fisheye has a focal range of 10-17mm and
1.7X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
15-25.5mm when used on a APS-C / DX format camera.
On the other hand, the Voigtlander 20mm F3.5 SL II 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.
