The type of photography that you are planning to use is an important decision factor. Here we have evaluated the HD Pentax-FA 77mm F1.8 Ltd and the Sigma 85mm 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. Sigma 85mm F1.4 EX DG HSM is the longer of the two lenses at 88mm. The HD Pentax-FA 77mm F1.8 Ltd with a length of 48mm, is 40mm shorter. Besides being longer, the Sigma 85mm F1.4 EX DG HSM also has a larger diameter of 86mm compared to the HD Pentax-FA 77mm F1.8 Ltd'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. HD Pentax-FA 77mm F1.8 Ltd weighs 270g, which means it is 455g (62%) lighter than the Sigma 85mm F1.4 EX DG HSM which has a weight of 725g.
Filter Threads
The HD Pentax-FA 77mm F1.8 Ltd has a filter size of 49mm whereas the Sigma 85mm 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 49mm filters that we recommend you to consider for the HD Pentax-FA 77mm F1.8 Ltd:
And these are the 77mm filters that we recommend for the Sigma 85mm F1.4 EX DG HSM:
Lens Mounts
The HD Pentax-FA 77mm F1.8 Ltd has the Pentax KAF lens mount whereas the Sigma 85mm F1.4 EX DG HSM has the Pentax KAF3 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 Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF3 Mount.
Sigma 85mm F1.4 EX DG HSM is also available in Canon EF , Nikon F (FX), Sony Alpha and Sigma SA mounts.
Focal Range
HD Pentax-FA 77mm F1.8 Ltd is a prime lens with fixed focal lenght of 77mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
115.5mm.
On the other hand, the Sigma 85mm F1.4 EX DG HSM is a prime lens with fixed focal lenght of 85mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 127.5mm.
