The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sony DT 18-70mm F3.5-5.6 and the Sigma 18-35mm F1.8 DC 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 18-35mm F1.8 DC HSM is the longer of the two lenses at 121mm. The Sony DT 18-70mm F3.5-5.6 with a length of 77mm, is 44mm shorter. Besides being longer, the Sigma 18-35mm F1.8 DC HSM also has a larger diameter of 78mm compared to the Sony DT 18-70mm F3.5-5.6's 66mm 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. Sony DT 18-70mm F3.5-5.6 weighs 235g, which means it is 575g (70%) lighter than the Sigma 18-35mm F1.8 DC HSM which has a weight of 810g.
Below you can find the dimension and weight table of the Standard Zoom Lenses in Sony Alpha Mount for size comparison purposes.
Standard Lenses in Sony Alpha Mount for Size Comparison
Filter Threads
The Sony DT 18-70mm F3.5-5.6 has a filter size of 55mm whereas the Sigma 18-35mm F1.8 DC HSM 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 55mm filters that we recommend you to consider for the Sony DT 18-70mm F3.5-5.6:
And these are the 72mm filters that we recommend for the Sigma 18-35mm F1.8 DC HSM:
Lens Mounts
Both the Sony DT 18-70mm F3.5-5.6 and the Sigma 18-35mm F1.8 DC HSM has the same Sony Alpha lens mount. Some of the latest released cameras that are compatible with the Sony Alpha lenses are Sony A68, Sony A77 II and Sony A58.
Sigma 18-35mm F1.8 DC HSM is also available in Canon EF , Pentax KAF, Sigma SA and Nikon F (DX) mounts.
Focal Range
Sony DT 18-70mm F3.5-5.6 has a focal range of 18-70mm and
3.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
27-105mm when used on a APS-C / DX format camera.
On the other hand, the Sigma 18-35mm F1.8 DC HSM has a focal range of 18-35mm and 1.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-52.5mm when used on a APS-C / DX format camera.
