The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon 20mm f2.8 USM and the Tokina 16-28mm f2.8 Pro FX 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. Tokina 16-28mm f2.8 Pro FX is the longer of the two lenses at 133mm. The Canon 20mm f2.8 USM with a length of 71mm, is 62mm shorter. Besides being longer, the Tokina 16-28mm f2.8 Pro FX also has a larger diameter of 90mm compared to the Canon 20mm f2.8 USM's 78mm 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 20mm f2.8 USM weighs 405g, which means it is 545g (57%) lighter than the Tokina 16-28mm f2.8 Pro FX which has a weight of 950g.
Lens Mounts
Both the Canon 20mm f2.8 USM and the Tokina 16-28mm f2.8 Pro FX 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.
Tokina 16-28mm f2.8 Pro FX is also available in Nikon F (FX) mount.
Focal Range
Canon 20mm f2.8 USM is a prime lens with fixed focal lenght of 20mm. When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of
32mm.
On the other hand, the Tokina 16-28mm f2.8 Pro FX has a focal range of 16-28mm 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 25.6 - 44.8mm.