The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 18-200mm F3.5-6.3 DC OS HSM C and the Sigma 17-70mm F2.8-4 DC OS HSM C 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 18-200mm F3.5-6.3 DC OS HSM C is the longer of the two lenses at 86mm. The Sigma 17-70mm F2.8-4 DC OS HSM C with a length of 82mm, is 4mm shorter. On the other hand, the Sigma 17-70mm F2.8-4 DC OS HSM C has a larger diameter of 79mm compared to the Sigma 18-200mm F3.5-6.3 DC OS HSM C's 71mm 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 18-200mm F3.5-6.3 DC OS HSM C weighs 430g, which means it is 35g (7%) lighter than the Sigma 17-70mm F2.8-4 DC OS HSM C which has a weight of 465g.
Filter Threads
The Sigma 18-200mm F3.5-6.3 DC OS HSM C has a filter size of 62mm whereas the Sigma 17-70mm F2.8-4 DC OS HSM C has a 72mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 62mm filters that we recommend you to consider for the Sigma 18-200mm F3.5-6.3 DC OS HSM C:
And these are the 72mm filters that we recommend for the Sigma 17-70mm F2.8-4 DC OS HSM C:
Lens Mounts
Both the Sigma 18-200mm F3.5-6.3 DC OS HSM C and the Sigma 17-70mm F2.8-4 DC OS HSM C has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon T8i, Canon 90D and Canon SL3.
Sigma 18-200mm F3.5-6.3 DC OS HSM C is also available in Nikon F (DX) , Pentax KAF3, Sony Alpha and Sigma SA mounts.
Sigma 17-70mm F2.8-4 DC OS HSM C is also available in Pentax KAF3 , Sony Alpha, Sigma SA and Nikon F (DX) mounts.
Focal Range
Sigma 18-200mm F3.5-6.3 DC OS HSM C has a focal range of 18-200mm and
11.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
28.8-320mm when used on a APS-C / DX format camera.
On the other hand, the Sigma 17-70mm F2.8-4 DC OS HSM C has a focal range of 17-70mm and 4.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27.2-112mm when used on a APS-C / DX format camera.