The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sony FE 28-70mm F3.5-5.6 OSS and the Sigma 30mm F2.8 EX DN 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 FE 28-70mm F3.5-5.6 OSS is the longer of the two lenses at 83mm. The Sigma 30mm F2.8 EX DN with a length of 39mm, is 44mm shorter. Besides being longer, the Sony FE 28-70mm F3.5-5.6 OSS also has a larger diameter of 73mm compared to the Sigma 30mm F2.8 EX DN's 61mm 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 30mm F2.8 EX DN weighs 135g, 54% (160g) lighter than the Sony FE 28-70mm F3.5-5.6 OSS's weight of 295g.
Filter Threads
The Sony FE 28-70mm F3.5-5.6 OSS has a filter size of 55mm whereas the Sigma 30mm F2.8 EX DN has a 46mm 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 FE 28-70mm F3.5-5.6 OSS:
And these are the 46mm filters that we recommend for the Sigma 30mm F2.8 EX DN:
Lens Mounts
Both the Sony FE 28-70mm F3.5-5.6 OSS and the Sigma 30mm F2.8 EX DN has the same Sony E lens mount. Some of the latest released cameras that are compatible with the Sony E lenses are Sony A9 III, Sony A7C Mark II and Sony A7CR.
Sigma 30mm F2.8 EX DN is also available in Micro Four Thirds mount.
Focal Range
Sony FE 28-70mm F3.5-5.6 OSS has a focal range of 28-70mm and
2.5X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
42 - 105mm.
On the other hand, the Sigma 30mm F2.8 EX DN is a prime lens with fixed focal lenght of 30mm which has an effective (full-frame 35mm equivalent) focal range of 45mm when used on a APS-C / DX format camera.