The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Carl Zeiss Distagon T3,5/18 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. Carl Zeiss Distagon T3,5/18 is the longer of the two lenses at 84mm. The Voigtlander 20mm F3.5 SL II with a length of 29mm, is 55mm shorter. Besides being longer, the Carl Zeiss Distagon T3,5/18 also has a larger diameter of 87mm 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, 56% (265g) lighter than the Carl Zeiss Distagon T3,5/18's weight of 470g.
Below you can find the dimension and weight table of the Wideangle Prime Lenses in Pentax KAF Mount for size comparison purposes.
Ultra-Wideangle Lenses in Pentax KAF Mount for Size Comparison
Filter Threads
The Carl Zeiss Distagon T3,5/18 has a filter size of 82mm whereas the Voigtlander 20mm F3.5 SL II has a 52mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 82mm filters that we recommend you to consider for the Carl Zeiss Distagon T3,5/18:
And these are the 52mm filters that we recommend for the Voigtlander 20mm F3.5 SL II:
Lens Mounts
Both the Carl Zeiss Distagon T3,5/18 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 Monochrome, Pentax KF and Pentax K-3 III.
Carl Zeiss Distagon T3,5/18 is also available in Canon EF and Nikon F (FX) mounts.
Voigtlander 20mm F3.5 SL II is also available in Canon EF and Nikon F (FX) mounts.
Focal Range
Carl Zeiss Distagon T3,5/18 is a prime lens with fixed focal lenght of 18mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
27mm.
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.