The EF 20mm f/2.8 USM Super wide-angle lens has a diagonal angle-of-view of 94-degrees, which are 48 more than what can be captured with a 50mm standard lens. The photos below show you the difference of what to expect when comparing the viewpoints between the 20mm and the 50mm lenses. What a 20mm viewpoint captures View from a 50mm lens One of them is a closer focusing distance of the EF 20mm f/2.8 USM vs. the EF 17-35mm f/2.8L USM zoom lens. The Super wide-angle lens has a closest focusing distance of 0.25m whereas the L-series zoom is at 0.42m. On paper, this may not seem like much but as the resulting photos below have shown, the 20mm Super wide-angle gives a bigger magnification than what is possible with the zoom lens. Closest distance of the EF 17-35L USM zoom Closest distance of the EF 20mm f/2.8 USM It can't be denied that the L-series zoom offers the advantage of having five different focal lengths in one compact design, the EF 20mm f/2.8 USM Super wide-angle lens is still very much lighter in overall weight and diameter, which is 405 grams plus a filter size of 72mm vs. 545 grams and 77mm for the former. Also, while the L-series zoom is more convenient to use due to its generous zooming range available, and much more practical in actual shooting situations like unfolding news events and other dramatic scenes, the single focal length viewpoint of the EF 20mm lens allows you the flexibility for artistic compositions as you can't change your viewpoints simply by turning the ring like a zoom does Another advantage of the EF 20mm f/2.8 USM Super wide-angle lens is its ability to use the Canon Extension Tube EF 12 (which can also be used with the L-series zoom). The maximum magnification of this 20mm lens at its closest focusing is 0.14X. With the Extension Tube EF 12 attached, the maximum magnifications will increase to 0.60X and 0.72X when the lens is focused at the infinity and its closest focusing distance respectively. Can be used with EF 12 Tube Magnification without EF 12     With EF 12: At infinity distance With EF 12: At closest distance The photos above of a key-chain featuring the metal endo-skull of the popular T-800 cyborg from the Terminator movie series, were photographed at first without the Extension Tube EF 12, then with the accessory fitted and the focusing distances shifted from infinity to the closest focusing distance. At the closest focusing distance, the front element of the 20mm lens was just half a centimeter away from touching the endo-skull. << Back to Main . 1 . 2 . 3 .