The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon RF 20-50mm F4 and the Sigma 17-40mm f1.8 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. Sigma 17-40mm f1.8 is the longer of the two lenses at 116mm. The Canon RF 20-50mm F4 with a length of 98mm, is 18mm shorter. On the other hand, the Canon RF 20-50mm F4 has a larger diameter of 80mm compared to the Sigma 17-40mm f1.8's 73mm 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 RF 20-50mm F4 weighs 420g, which means it is 115g (21%) lighter than the Sigma 17-40mm f1.8 which has a weight of 535g.
Below you can find the dimension and weight table of the Standard Zoom Lenses in Canon RF Mount for size comparison purposes.
Standard Lenses in Canon RF Mount for Size Comparison
Filter Threads
Both the Canon RF 20-50mm F4 and the Sigma 17-40mm f1.8 have the same Filter thread size of 67mm.
Below are links to the 67mm filters that we recommend you to consider for these lenses:
Lens Mounts
Both the Canon RF 20-50mm F4 and the Sigma 17-40mm f1.8 has the same Canon RF lens mount. Some of the latest released cameras that are compatible with the Canon RF lenses are Canon R6 V, Canon R6 III and Canon C50.
Sigma 17-40mm f1.8 is also available in Sony E , Leica L and Fujifilm X mounts.
Focal Range
Canon RF 20-50mm F4 has a focal range of 20-50mm and
2.5X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of
32 - 80mm.
On the other hand, the Sigma 17-40mm f1.8 has a focal range of 17-40mm and 2.4X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27.2-64mm when used on a APS-C / DX format camera.
