The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sony FE 100mm F2.8 STF GM and the Zeiss Loxia 85mm F2.4 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. Sony FE 100mm F2.8 STF GM is the longer of the two lenses at 118mm. The Zeiss Loxia 85mm F2.4 with a length of 95mm, is 23mm shorter. Besides being longer, the Sony FE 100mm F2.8 STF GM also has a larger diameter of 85mm compared to the Zeiss Loxia 85mm F2.4'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. Zeiss Loxia 85mm F2.4 weighs 594g, 15% (106g) lighter than the Sony FE 100mm F2.8 STF GM's weight of 700g.
Below you can find the dimension and weight table of the Telephoto Prime Lenses in Sony E Mount for size comparison purposes.
Telephoto Lenses in Sony E Mount for Size Comparison
Filter Threads
The Sony FE 100mm F2.8 STF GM has a filter size of 72mm whereas the Zeiss Loxia 85mm F2.4 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 72mm filters that we recommend you to consider for the Sony FE 100mm F2.8 STF GM:
And these are the 52mm filters that we recommend for the Zeiss Loxia 85mm F2.4:
Lens Mounts
Both the Sony FE 100mm F2.8 STF GM and the Zeiss Loxia 85mm F2.4 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
Sony FE 100mm F2.8 STF GM is a prime lens with fixed focal lenght of 100mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
150mm.
On the other hand, the Zeiss Loxia 85mm F2.4 is a prime lens with fixed focal lenght of 85mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 127.5mm.