The type of photography that you are planning to use is an important decision factor. Here we have evaluated the HD Pentax-FA 31mm F1.8 Ltd and the Sigma 30mm F1.4 EX 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. HD Pentax-FA 31mm F1.8 Ltd is the longer of the two lenses at 69mm. The Sigma 30mm F1.4 EX DC HSM with a length of 59mm, is 10mm shorter. On the other hand, the Sigma 30mm F1.4 EX DC HSM has a larger diameter of 77mm compared to the HD Pentax-FA 31mm F1.8 Ltd'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. HD Pentax-FA 31mm F1.8 Ltd weighs 341g, which means it is 89g (20%) lighter than the Sigma 30mm F1.4 EX DC HSM which has a weight of 430g.
Filter Threads
The HD Pentax-FA 31mm F1.8 Ltd has a filter size of 58mm whereas the Sigma 30mm F1.4 EX 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 HD Pentax-FA 31mm F1.8 Ltd:
And these are the 62mm filters that we recommend for the Sigma 30mm F1.4 EX DC HSM:
Lens Mounts
Both the HD Pentax-FA 31mm F1.8 Ltd and the Sigma 30mm F1.4 EX DC HSM 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 30mm F1.4 EX DC HSM is also available in Canon EF-S , Nikon F (DX), Four Thirds, Sony Alpha and Sigma SA mounts.
Focal Range
HD Pentax-FA 31mm F1.8 Ltd 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 EX DC HSM 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.
