The type of photography that you are planning to use is an important decision factor. Here we have evaluated the ZEISS Loxia 21mm F2.8 and the Sony E 20mm F2.8 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. ZEISS Loxia 21mm F2.8 is the longer of the two lenses at 72mm. The Sony E 20mm F2.8 with a length of 20mm, is 52mm shorter. On the other hand, the Sony E 20mm F2.8 has a larger diameter of 63mm compared to the ZEISS Loxia 21mm F2.8's 62mm 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. Sony E 20mm F2.8 weighs 69g, 82% (325g) lighter than the ZEISS Loxia 21mm F2.8's weight of 394g.
Below you can find the dimension and weight table of the Wideangle Prime Lenses in Sony E Mount for size comparison purposes.
Wideangle Lenses in Sony E Mount for Size Comparison
Filter Threads
The ZEISS Loxia 21mm F2.8 has a filter size of 52mm whereas the Sony E 20mm F2.8 has a 49mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 52mm filters that we recommend you to consider for the ZEISS Loxia 21mm F2.8:
And these are the 49mm filters that we recommend for the Sony E 20mm F2.8:
Lens Mounts
Both the ZEISS Loxia 21mm F2.8 and the Sony E 20mm F2.8 has the same Sony E lens mount. Some of the latest released cameras that are compatible with the Sony E lenses are Sony A9 III, Sony A7C Mark II and Sony A7CR.
Focal Range
ZEISS Loxia 21mm F2.8 is a prime lens with fixed focal lenght of 21mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
31.5mm.
On the other hand, the Sony E 20mm F2.8 is a prime lens with fixed focal lenght of 20mm which has an effective (full-frame 35mm equivalent) focal range of 30mm when used on a APS-C / DX format camera.