The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 24-70mm F2.8 EX DG and the Sigma 17-50mm F2.8 EX DC OS 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. Sigma 24-70mm F2.8 EX DG is the longer of the two lenses at 116mm. The Sigma 17-50mm F2.8 EX DC OS HSM with a length of 92mm, is 24mm shorter. Besides being longer, the Sigma 24-70mm F2.8 EX DG also has a larger diameter of 89mm compared to the Sigma 17-50mm F2.8 EX DC OS HSM's 84mm 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 17-50mm F2.8 EX DC OS HSM weighs 565g, 20% (150g) lighter than the Sigma 24-70mm F2.8 EX DG's weight of 715g.
Below you can find the dimension and weight table of the Standard Zoom Lenses in Canon EF Mount for size comparison purposes.
Standard Zoom Lenses in Canon EF Mount for Size Comparison
Lens Mounts
Both the Sigma 24-70mm F2.8 EX DG and the Sigma 17-50mm F2.8 EX DC OS HSM has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon 1D X III, Canon 6D MII and Canon 5D MIV.
Sigma 24-70mm F2.8 EX DG is also available in Pentax KAF , Sony Alpha, Sigma SA and Nikon F (FX) mounts.
Sigma 17-50mm F2.8 EX DC OS HSM is also available in Pentax KAF3 , Sony Alpha, Sigma SA and Nikon F (DX) mounts.
Focal Range
Sigma 24-70mm F2.8 EX DG has a focal range of 24-70mm and 2.9X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 38.4 - 112mm.
Sigma 17-50mm F2.8 EX DC OS HSM has a focal range of 17-50mm and 2.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27.2-80mm when used on a APS-C / DX format camera.