The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 17-70mm F2.8-4 DC OS HSM 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 a crucial factor to consider when comparing two lenses. Sigma 17-50mm F2.8 EX DC OS HSM is the longer of the two lenses at 92mm. The Sigma 17-70mm F2.8-4 DC OS HSM with a length of 89mm, is 3mm shorter. Besides being longer, the Sigma 17-50mm F2.8 EX DC OS HSM also has a larger diameter of 84mm compared to the Sigma 17-70mm F2.8-4 DC OS HSM's 79mm 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. Sigma 17-70mm F2.8-4 DC OS HSM weighs 520g, which means it is 45g (7%) lighter than the Sigma 17-50mm F2.8 EX DC OS HSM which has a weight of 565g.
Below you can find the dimension and weight table of the Standard Zoom Lenses in Sigma SA Mount for size comparison purposes.
Standard Lenses in Sigma SA Mount for Size Comparison
Filter Threads
The Sigma 17-70mm F2.8-4 DC OS HSM has a filter size of 72mm whereas the Sigma 17-50mm F2.8 EX DC OS HSM has a 77mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 72mm filters that we recommend you to consider for the Sigma 17-70mm F2.8-4 DC OS HSM:
And these are the 77mm filters that we recommend for the Sigma 17-50mm F2.8 EX DC OS HSM:
Lens Mounts
Both the Sigma 17-70mm F2.8-4 DC OS HSM and the Sigma 17-50mm F2.8 EX DC OS HSM has the same Sigma SA lens mount. Some of the latest released cameras that are compatible with the Sigma SA lenses are Sigma SD1 Merrill, Sigma SD1 and .
Sigma 17-70mm F2.8-4 DC OS HSM is also available in Canon EF , Pentax KAF3, Sony Alpha and Nikon F (DX) mounts.
Sigma 17-50mm F2.8 EX DC OS HSM is also available in Canon EF , Pentax KAF3, Sony Alpha and Nikon F (DX) mounts.
Focal Range
Sigma 17-70mm F2.8-4 DC OS HSM has a focal range of 17-70mm and
4.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
25.5-105mm when used on a APS-C / DX format camera.
On the other hand, the 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 25.5-75mm when used on a APS-C / DX format camera.