The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax 40mm F2.8 L and the Pentax D-FA 50mm F2.8 Macro 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 D-FA 50mm F2.8 Macro is the longer of the two lenses at 60mm. The Pentax 40mm F2.8 L with a length of 15mm, is 45mm shorter. Besides being longer, the Pentax D-FA 50mm F2.8 Macro also has a larger diameter of 68mm compared to the Pentax 40mm F2.8 L'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 40mm F2.8 L weighs 90g, which means it is 175g (66%) lighter than the Pentax D-FA 50mm F2.8 Macro which has a weight of 265g.
Filter Threads
Both the Pentax 40mm F2.8 L and the Pentax D-FA 50mm F2.8 Macro have the same Filter thread size of 49mm.
Below are links to the 49mm filters that we recommend you to consider for these lenses:
Lens Mounts
Both the Pentax 40mm F2.8 L and the Pentax D-FA 50mm F2.8 Macro 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 Monochrome, Pentax KF and Pentax K-3 III.
Pentax 40mm F2.8 L is also available in Pentax KAF mount.
Focal Range
Pentax 40mm F2.8 L is a prime lens with fixed focal lenght of 40mm which has an effective (full-frame 35mm equivalent) focal range of
60mm when used on a APS-C / DX format camera.
On the other hand, the Pentax D-FA 50mm F2.8 Macro 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.