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
Size of a lens is an important deciding factor 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 ZEISS Loxia 21mm F2.8's 62mm diameter.
Weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer 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 Prime Lenses in Sony E Mount for Size Comparison
Both ZEISS Loxia 21mm F2.8 and 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 A7R V, Sony FX30 and Sony A7 IV.
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 an 35mm (FF) equivalent of 31.5mm.
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.