The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon 20-35mm f3.5-4.5 USM and the Canon 17-40mm f4.0L 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 17-40mm f4.0L USM is the longer of the two lenses at 97mm. The Canon 20-35mm f3.5-4.5 USM with a length of 69mm, is 28mm shorter. On the other hand, there is no difference between the max diameters of these lenses, both coming at 84mm.
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 20-35mm f3.5-4.5 USM weighs 340g, which means it is 160g (31%) lighter than the Canon 17-40mm f4.0L USM which has a weight of 500g.
Below you can find the dimension and weight table of the Wideangle Zoom Lenses in Canon EF Mount for size comparison purposes.
Ultra-Wideangle Lenses in Canon EF Mount for Size Comparison
Filter Threads
Both the Canon 20-35mm f3.5-4.5 USM and the Canon 17-40mm f4.0L USM have the same Filter thread size of 77mm.
Below are links to the 77mm filters that we recommend you to consider for these lenses:
Lens Mounts
Both the Canon 20-35mm f3.5-4.5 USM and the Canon 17-40mm f4.0L 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 20-35mm f3.5-4.5 USM has a focal range of 20-35mm and
1.8X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of
32 - 56mm.
On the other hand, the Canon 17-40mm f4.0L USM has a focal range of 17-40mm and 2.4X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 27.2 - 64mm.