The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 120-400mm F4.5-5.6 DG OS HSM and the Canon 55-250mm f4-5.6 IS STM 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 120-400mm F4.5-5.6 DG OS HSM is the longer of the two lenses at 203mm. The Canon 55-250mm f4-5.6 IS STM with a length of 111mm, is 92mm shorter. Besides being longer, the Sigma 120-400mm F4.5-5.6 DG OS HSM also has a larger diameter of 92mm compared to the Canon 55-250mm f4-5.6 IS STM's 70mm 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 55-250mm f4-5.6 IS STM weighs 375g, 77% (1265g) lighter than the Sigma 120-400mm F4.5-5.6 DG OS HSM's weight of 1640g.
Filter Threads
The Sigma 120-400mm F4.5-5.6 DG OS HSM has a filter size of 77mm whereas the Canon 55-250mm f4-5.6 IS STM has a 58mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 77mm filters that we recommend you to consider for the Sigma 120-400mm F4.5-5.6 DG OS HSM:
And these are the 58mm filters that we recommend for the Canon 55-250mm f4-5.6 IS STM:
Lens Mounts
The Sigma 120-400mm F4.5-5.6 DG OS HSM has the Canon EF lens mount whereas the Canon 55-250mm f4-5.6 IS STM has the Canon EF-S lens mount. Some of the latest released cameras that are compatible with these mounts are Blackmagic URSA 12K LF, Z CAM E2-F6 II 6K and Z CAM E2-S6 II 6K for the Canon EF Mount and Canon T8i, Canon 90D and Canon SL3 for the Canon EF-S Mount.
Sigma 120-400mm F4.5-5.6 DG OS HSM is also available in the Sigma SA and Nikon F (FX) mounts.
Focal Range
Sigma 120-400mm F4.5-5.6 DG OS HSM has a focal range of 120-400mm and
3.3X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of
192 - 640mm.
On the other hand, the Canon 55-250mm f4-5.6 IS STM has a focal range of 55-250mm and 4.5X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 88-400mm when used on a APS-C / DX format camera.
