The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon 16-35mm F2.8L III 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 16-35mm F2.8L III with a length of 128mm, is 221mm shorter. Besides being longer, the Canon 400mm f2.8L IS USM also has a larger diameter of 163mm compared to the Canon 16-35mm F2.8L III'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 16-35mm F2.8L III weighs 790g, which means it is 4580g (85%) lighter than the Canon 400mm f2.8L IS USM which has a weight of 5370g.
Filter Threads
The Canon 16-35mm F2.8L III has a filter size of 82mm 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 82mm filters that we recommend you to consider for the Canon 16-35mm F2.8L III:
And these are the 52mm filters that we recommend for the Canon 400mm f2.8L IS USM:
Lens Mounts
Both the Canon 16-35mm F2.8L III 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 16-35mm F2.8L III has a focal range of 16-35mm and
2.2X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of
25.6 - 56mm.
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.