The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon RF 135mm F1.8 L IS USM and the Sigma 35mm F1.4 DG HSM for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is an important deciding factor when comparing two lenses. Canon RF 135mm F1.8 L IS USM is the longer of the two lenses at 130mm. The Sigma 35mm F1.4 DG HSM with a length of 94mm, is 36mm shorter. Besides being longer, the Canon RF 135mm F1.8 L IS USM also has a larger diameter of 89mm compared to the Sigma 35mm F1.4 DG HSM's 77mm diameter.
The weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Sigma 35mm F1.4 DG HSM weighs 665g, 28% (270g) lighter than the Canon RF 135mm F1.8 L IS USM's weight of 935g.
Lens Mounts
The Canon RF 135mm F1.8 L IS USM has the Canon RF lens mount whereas the Sigma 35mm F1.4 DG HSM has the Canon EF lens mount. Some of the latest released cameras that are compatible with these mounts are Canon R8, Canon R50 and Canon R6 II for the Canon RF Mount and Canon 1D X III, Canon 6D MII and Canon 5D MIV for the Canon EF Mount.
Sigma 35mm F1.4 DG HSM is also available in Pentax KAF3 , Sony Alpha, Sigma SA, Nikon F (FX) and Leica L mounts.
Focal Range
Canon RF 135mm F1.8 L IS USM is a prime lens with fixed focal lenght of 135mm. When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 216mm.
Sigma 35mm F1.4 DG HSM is a prime lens with fixed focal lenght of 35mm. When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 56mm.