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 50mm F1.4 EX DG 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. Sony DT 18-70mm F3.5-5.6 is the longer of the two lenses at 77mm. The Sigma 50mm F1.4 EX DG HSM with a length of 68mm, is 9mm shorter. On the other hand, the Sigma 50mm F1.4 EX DG HSM has a larger diameter of 85mm 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 270g (53%) lighter than the Sigma 50mm F1.4 EX DG HSM which has a weight of 505g.
Filter Threads
The Sony DT 18-70mm F3.5-5.6 has a filter size of 55mm whereas the Sigma 50mm F1.4 EX DG 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 55mm filters that we recommend you to consider for the Sony DT 18-70mm F3.5-5.6:
And these are the 77mm filters that we recommend for the Sigma 50mm F1.4 EX DG HSM:
Lens Mounts
Both the Sony DT 18-70mm F3.5-5.6 and the Sigma 50mm F1.4 EX DG 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 50mm F1.4 EX DG HSM is also available in Canon EF , Pentax KAF3, Sigma SA, Nikon F (FX) and Four Thirds 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 50mm F1.4 EX DG HSM is a prime lens with fixed focal lenght of 50mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 75mm.
