The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon RF 28-70mm F2L USM and the Sigma 120-300mm F2.8 EX DG 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. Sigma 120-300mm F2.8 EX DG HSM is the longer of the two lenses at 271mm. The Canon RF 28-70mm F2L USM with a length of 140mm, is 131mm shorter. Besides being longer, the Sigma 120-300mm F2.8 EX DG HSM also has a larger diameter of 113mm compared to the Canon RF 28-70mm F2L USM's 104mm 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 28-70mm F2L USM weighs 1430g, which means it is 1170g (44%) lighter than the Sigma 120-300mm F2.8 EX DG HSM which has a weight of 2600g.
Filter Threads
The Canon RF 28-70mm F2L USM has a filter size of 95mm whereas the Sigma 120-300mm F2.8 EX DG HSM has a 105mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 95mm filters that we recommend you to consider for the Canon RF 28-70mm F2L USM:
And these are the 105mm filters that we recommend for the Sigma 120-300mm F2.8 EX DG HSM:
Lens Mounts
The Canon RF 28-70mm F2L USM has the Canon RF lens mount whereas the Sigma 120-300mm F2.8 EX DG HSM has the Canon EF lens mount. Some of the latest released cameras that are compatible with these mounts are Canon R6 V, Canon R6 III and Canon C50 for the Canon RF Mount and Blackmagic URSA 12K LF, Z CAM E2-F6 II 6K and Z CAM E2-S6 II 6K for the Canon EF Mount.
Sigma 120-300mm F2.8 EX DG HSM is also available in Sigma SA and Nikon F (FX) mounts.
Focal Range
Canon RF 28-70mm F2L USM has a focal range of 28-70mm 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
44.8 - 112mm.
On the other hand, the Sigma 120-300mm F2.8 EX DG HSM has a focal range of 120-300mm 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 192 - 480mm.
