The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax FA 31mm F1.8 L and the Sigma 30mm F1.4 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. Pentax FA 31mm F1.8 L is the longer of the two lenses at 69mm. The Sigma 30mm F1.4 DC HSM with a length of 63mm, is 6mm shorter. On the other hand, the Sigma 30mm F1.4 DC HSM has a larger diameter of 74mm compared to the Pentax FA 31mm F1.8 L's 65mm 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 31mm F1.8 L weighs 345g, which means it is 90g (20%) lighter than the Sigma 30mm F1.4 DC HSM which has a weight of 435g.
Filter Threads
The Pentax FA 31mm F1.8 L has a filter size of 58mm whereas the Sigma 30mm F1.4 DC HSM has a 62mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 58mm filters that we recommend you to consider for the Pentax FA 31mm F1.8 L:
And these are the 62mm filters that we recommend for the Sigma 30mm F1.4 DC HSM:
Lens Mounts
The Pentax FA 31mm F1.8 L has the Pentax KAF lens mount whereas the Sigma 30mm F1.4 DC HSM has the Canon EF lens mount. Some of the latest released cameras that are compatible with these mounts are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF Mount and Canon T8i, Canon 90D and Canon SL3 for the Canon EF Mount.
Sigma 30mm F1.4 DC HSM is also available in Nikon F (DX) and Sigma SA mounts.
Focal Range
Pentax FA 31mm F1.8 L is a prime lens with fixed focal lenght of 31mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
46.5mm.
On the other hand, the Sigma 30mm F1.4 DC HSM is a prime lens with fixed focal lenght of 30mm which has an effective (full-frame 35mm equivalent) focal range of 48mm when used on a APS-C / DX format camera.
