The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 16mm F1.4 DC DN E and the ZEISS Loxia 21mm F2.8 for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is an important deciding factor when comparing two lenses. Sigma 16mm F1.4 DC DN E is the longer of the two lenses at 92mm. The ZEISS Loxia 21mm F2.8 with a length of 72mm, is 20mm shorter. Besides being longer, the Sigma 16mm F1.4 DC DN E also has a larger diameter of 72mm compared to the ZEISS Loxia 21mm F2.8's 62mm diameter.
The 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. ZEISS Loxia 21mm F2.8 weighs 394g, 2% (11g) lighter than the Sigma 16mm F1.4 DC DN E's weight of 405g.
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 the Sigma 16mm F1.4 DC DN E and the ZEISS Loxia 21mm 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 FX30, Sony ZV-E10 and Sony A6600.
Sigma 16mm F1.4 DC DN E is a prime lens with fixed focal lenght of 16mm which has an effective (full-frame 35mm equivalent) focal range of 24mm when used on a APS-C / DX format camera. 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.