The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax 21mm F3.2 AL L and the Carl Zeiss Distagon T2/28 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 T2/28 is the longer of the two lenses at 93mm. The Pentax 21mm F3.2 AL L with a length of 25mm, is 68mm shorter. Besides being longer, the Carl Zeiss Distagon T2/28 also has a larger diameter of 64mm compared to the Pentax 21mm F3.2 AL L'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. Pentax 21mm F3.2 AL L weighs 140g, which means it is 380g (73%) lighter than the Carl Zeiss Distagon T2/28 which has a weight of 520g.
Below you can find the dimension and weight table of the Wideangle Prime Lenses in Pentax KAF Mount for size comparison purposes.
Wideangle Lenses in Pentax KAF Mount for Size Comparison
Filter Threads
The Pentax 21mm F3.2 AL L has a filter size of 49mm whereas the Carl Zeiss Distagon T2/28 has a 58mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 49mm filters that we recommend you to consider for the Pentax 21mm F3.2 AL L:
And these are the 58mm filters that we recommend for the Carl Zeiss Distagon T2/28:
Lens Mounts
Both the Pentax 21mm F3.2 AL L and the Carl Zeiss Distagon T2/28 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.
Pentax 21mm F3.2 AL L is also available in Pentax KAF mount.
Carl Zeiss Distagon T2/28 is also available in Canon EF and Nikon F (FX) mounts.
Focal Range
Pentax 21mm F3.2 AL L is a prime lens with fixed focal lenght of 21mm which has an effective (full-frame 35mm equivalent) focal range of
31.5mm when used on a APS-C / DX format camera.
On the other hand, the Carl Zeiss Distagon T2/28 is a prime lens with fixed focal lenght of 28mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 42mm.