The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon 85mm f1.2L II USM and the Canon EF 400mm F2.8L IS III USM 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. Canon EF 400mm F2.8L IS III USM is the longer of the two lenses at 343mm. The Canon 85mm f1.2L II USM with a length of 84mm, is 259mm shorter. Besides being longer, the Canon EF 400mm F2.8L IS III USM also has a larger diameter of 163mm compared to the Canon 85mm f1.2L II USM's 92mm 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. Canon 85mm f1.2L II USM weighs 1025g, which means it is 1815g (63%) lighter than the Canon EF 400mm F2.8L IS III USM which has a weight of 2840g.
Filter Threads
The Canon 85mm f1.2L II USM has a filter size of 72mm whereas the Canon EF 400mm F2.8L IS III USM 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 Canon 85mm f1.2L II USM:
And these are the 52mm filters that we recommend for the Canon EF 400mm F2.8L IS III USM:
Lens Mounts
Both the Canon 85mm f1.2L II USM and the Canon EF 400mm F2.8L IS III USM has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon 1D X III, Canon 6D MII and Canon 5D MIV.
Focal Range
Canon 85mm f1.2L II USM is a prime lens with fixed focal lenght of 85mm. When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of
136mm.
On the other hand, the Canon EF 400mm F2.8L IS III USM is a prime lens with fixed focal lenght of 400mm. When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 640mm.