The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon 400mm F4 DO IS II USM and the Canon 85mm f1.2L II 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 400mm F4 DO IS II USM is the longer of the two lenses at 233mm. The Canon 85mm f1.2L II USM with a length of 84mm, is 149mm shorter. Besides being longer, the Canon 400mm F4 DO IS II USM also has a larger diameter of 128mm compared to the Canon 85mm f1.2L II USM's 92mm diameter.
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Below you can find a scaled side-by-side image of Canon 400mm F4 DO IS II USM and Canon 85mm f1.2L II USM to get a better idea of how their sizes compare in real life.
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, 51% (1075g) lighter than the Canon 400mm F4 DO IS II USM's weight of 2100g.
Filter Threads
The Canon 400mm F4 DO IS II USM has a filter size of 52mm whereas the Canon 85mm f1.2L II USM has a 72mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 52mm filters that we recommend you to consider for the Canon 400mm F4 DO IS II USM:
And these are the 72mm filters that we recommend for the Canon 85mm f1.2L II USM:
Lens Mounts
Both the Canon 400mm F4 DO IS II USM and the Canon 85mm f1.2L II 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 400mm F4 DO IS II 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.
On the other hand, the 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.