The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon EF 70-200 F2.8L IS III USM and the Canon 400mm f2.8L IS 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 f2.8L IS USM is the longer of the two lenses at 349mm. The Canon EF 70-200 F2.8L IS III USM with a length of 199mm, is 150mm shorter. Besides being longer, the Canon 400mm f2.8L IS USM also has a larger diameter of 163mm compared to the Canon EF 70-200 F2.8L IS III USM's 89mm 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 EF 70-200 F2.8L IS III USM weighs 1440g, which means it is 3930g (73%) lighter than the Canon 400mm f2.8L IS USM which has a weight of 5370g.
Filter Threads
The Canon EF 70-200 F2.8L IS III USM has a filter size of 77mm whereas the Canon 400mm f2.8L IS 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 77mm filters that we recommend you to consider for the Canon EF 70-200 F2.8L IS III USM:
And these are the 52mm filters that we recommend for the Canon 400mm f2.8L IS USM:
Lens Mounts
Both the Canon EF 70-200 F2.8L IS III USM and the Canon 400mm f2.8L IS 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 EF 70-200 F2.8L IS III USM has a focal range of 70-200mm and
2.9X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of
112 - 320mm.
On the other hand, the Canon 400mm f2.8L IS 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.