The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 24-70mm F2.8 EX DG and the Pentax FA 50mm F1.4 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 24-70mm F2.8 EX DG is the longer of the two lenses at 116mm. The Pentax FA 50mm F1.4 with a length of 38mm, is 78mm shorter. Besides being longer, the Sigma 24-70mm F2.8 EX DG also has a larger diameter of 89mm compared to the Pentax FA 50mm F1.4's 64mm 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. Pentax FA 50mm F1.4 weighs 220g, 69% (495g) lighter than the Sigma 24-70mm F2.8 EX DG's weight of 715g.
Filter Threads
The Sigma 24-70mm F2.8 EX DG has a filter size of 82mm whereas the Pentax FA 50mm F1.4 has a 49mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 82mm filters that we recommend you to consider for the Sigma 24-70mm F2.8 EX DG:
And these are the 49mm filters that we recommend for the Pentax FA 50mm F1.4:
Lens Mounts
Both the Sigma 24-70mm F2.8 EX DG and the Pentax FA 50mm F1.4 has the same Pentax KAF lens mount. Some of the latest released cameras that are compatible with the Pentax KAF lenses are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III.
Sigma 24-70mm F2.8 EX DG is also available in the Canon EF , Sony Alpha, Sigma SA and Nikon F (FX) mounts.
Pentax FA 50mm F1.4 is also available in Pentax KAF mount.
Focal Range
Sigma 24-70mm F2.8 EX DG has a focal range of 24-70mm and
2.9X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
36 - 105mm.
On the other hand, the Pentax FA 50mm F1.4 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.
