The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Zeiss Otus 85mm f1.4 and the Sigma 18-125mm F3.8-5.6 DC HSM 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 Otus 85mm f1.4 is the longer of the two lenses at 128mm. The Sigma 18-125mm F3.8-5.6 DC HSM with a length of 89mm, is 39mm shorter. Besides being longer, the Zeiss Otus 85mm f1.4 also has a larger diameter of 88mm compared to the Sigma 18-125mm F3.8-5.6 DC HSM's 74mm 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. Sigma 18-125mm F3.8-5.6 DC HSM weighs 490g, 52% (550g) lighter than the Zeiss Otus 85mm f1.4's weight of 1040g.
Filter Threads
The Zeiss Otus 85mm f1.4 has a filter size of 77mm whereas the Sigma 18-125mm F3.8-5.6 DC HSM has a 62mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 77mm filters that we recommend you to consider for the Zeiss Otus 85mm f1.4:
And these are the 62mm filters that we recommend for the Sigma 18-125mm F3.8-5.6 DC HSM:
Lens Mounts
The Zeiss Otus 85mm f1.4 has the Sony E lens mount whereas the Sigma 18-125mm F3.8-5.6 DC HSM has the Sony Alpha lens mount. Some of the latest released cameras that are compatible with these mounts are Sony FX5, Sony A7R VI and Sony A7 V for the Sony E Mount and Sony A68, Sony A77 II and Sony A58 for the Sony Alpha Mount.
Zeiss Otus 85mm f1.4 is also available in the Canon EF , Nikon F (FX), Canon RF and Nikon Z mounts.
Sigma 18-125mm F3.8-5.6 DC HSM is also available in Pentax KAF3 mount.
Focal Range
Zeiss Otus 85mm f1.4 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.
On the other hand, the Sigma 18-125mm F3.8-5.6 DC HSM has a focal range of 18-125mm and 6.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-187.5mm when used on a APS-C / DX format camera.
