The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax DA 55mm F1.4 SDM and the Pentax 50mm F1.8 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 55mm F1.4 SDM is the longer of the two lenses at 66mm. The Pentax 50mm F1.8 with a length of 39mm, is 27mm shorter. Besides being longer, the Pentax DA 55mm F1.4 SDM also has a larger diameter of 70mm compared to the Pentax 50mm F1.8's 63mm 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 50mm F1.8 weighs 122g, 67% (253g) lighter than the Pentax DA 55mm F1.4 SDM's weight of 375g.
Filter Threads
The Pentax DA 55mm F1.4 SDM has a filter size of 58mm whereas the Pentax 50mm F1.8 has a 52mm 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 55mm F1.4 SDM:
And these are the 52mm filters that we recommend for the Pentax 50mm F1.8:
Lens Mounts
The Pentax DA 55mm F1.4 SDM has the Pentax KAF3 lens mount whereas the Pentax 50mm F1.8 has the Pentax KAF lens mount. Some of the latest released cameras that are compatible with these mounts are , and for the Pentax KAF3 Mount and Pentax K-3 III Monochrome, Pentax KF and Pentax K-3 III for the Pentax KAF Mount.
Focal Range
Pentax DA 55mm F1.4 SDM is a prime lens with fixed focal lenght of 55mm which has an effective (full-frame 35mm equivalent) focal range of
82.5mm when used on a APS-C / DX format camera.
On the other hand, the Pentax 50mm F1.8 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.