The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon RF 15-35mm F2.8L IS USM and the Sigma 18-35mm F1.8 DC HSM 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 RF 15-35mm F2.8L IS USM is the longer of the two lenses at 127mm. The Sigma 18-35mm F1.8 DC HSM with a length of 121mm, is 6mm shorter. Besides being longer, the Canon RF 15-35mm F2.8L IS USM also has a larger diameter of 89mm compared to the Sigma 18-35mm F1.8 DC HSM's 78mm diameter.
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Below you can find a scaled side-by-side image of Canon RF 15-35mm F2.8L IS USM and Sigma 18-35mm F1.8 DC HSM to get a better idea of how their sizes compare in real life.
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. Sigma 18-35mm F1.8 DC HSM weighs 810g, 3% (30g) lighter than the Canon RF 15-35mm F2.8L IS USM's weight of 840g.
Filter Threads
The Canon RF 15-35mm F2.8L IS USM has a filter size of 82mm whereas the Sigma 18-35mm F1.8 DC HSM has a 72mm 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 RF 15-35mm F2.8L IS USM:
And these are the 72mm filters that we recommend for the Sigma 18-35mm F1.8 DC HSM:
Lens Mounts
The Canon RF 15-35mm F2.8L IS USM has the Canon RF lens mount whereas the Sigma 18-35mm F1.8 DC HSM has the Canon EF lens mount. Some of the latest released cameras that are compatible with these mounts are Canon R100, Canon R8 and Canon R50 for the Canon RF Mount and Canon T8i, Canon 90D and Canon SL3 for the Canon EF Mount.
Sigma 18-35mm F1.8 DC HSM is also available in Pentax KAF , Sony Alpha, Sigma SA and Nikon F (DX) mounts.
Focal Range
Canon RF 15-35mm F2.8L IS USM has a focal range of 15-35mm and
2.3X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of
24 - 56mm.
On the other hand, the Sigma 18-35mm F1.8 DC HSM has a focal range of 18-35mm and 1.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 28.8-56mm when used on a APS-C / DX format camera.