The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax DA 18-50mm F4.5-5.6 DC WR RE and the Sigma 50mm 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. Pentax DA 18-50mm F4.5-5.6 DC WR RE is the longer of the two lenses at 71mm. The Sigma 50mm F1.4 EX DG HSM with a length of 68mm, is 3mm shorter. On the other hand, the Sigma 50mm F1.4 EX DG HSM has a larger diameter of 85mm compared to the Pentax DA 18-50mm F4.5-5.6 DC WR RE's 41mm 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 DA 18-50mm F4.5-5.6 DC WR RE weighs 158g, which means it is 347g (68%) lighter than the Sigma 50mm F1.4 EX DG HSM which has a weight of 505g.
Filter Threads
The Pentax DA 18-50mm F4.5-5.6 DC WR RE has a filter size of 58mm whereas the Sigma 50mm 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 58mm filters that we recommend you to consider for the Pentax DA 18-50mm F4.5-5.6 DC WR RE:
And these are the 77mm filters that we recommend for the Sigma 50mm F1.4 EX DG HSM:
Lens Mounts
Both the Pentax DA 18-50mm F4.5-5.6 DC WR RE and the Sigma 50mm F1.4 EX DG HSM has the same Pentax KAF3 lens mount. Some of the latest released cameras that are compatible with the Pentax KAF3 lenses are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III.
Sigma 50mm F1.4 EX DG HSM is also available in Canon EF , Sony Alpha, Sigma SA, Nikon F (FX) and Four Thirds mounts.
Focal Range
Pentax DA 18-50mm F4.5-5.6 DC WR RE has a focal range of 18-50mm and
2.8X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
27-75mm when used on a APS-C / DX format camera.
On the other hand, the Sigma 50mm F1.4 EX DG HSM 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.
