The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Carl Zeiss Makro-Planar T2/50 and the Pentax 40mm F2.8 L 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. Carl Zeiss Makro-Planar T2/50 is the longer of the two lenses at 88mm. The Pentax 40mm F2.8 L with a length of 15mm, is 73mm shorter. Besides being longer, the Carl Zeiss Makro-Planar T2/50 also has a larger diameter of 72mm 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 80g, 84% (450g) lighter than the Carl Zeiss Makro-Planar T2/50's weight of 530g.
Filter Threads
The Carl Zeiss Makro-Planar T2/50 has a filter size of 67mm whereas the Pentax 40mm F2.8 L has a 49mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 67mm filters that we recommend you to consider for the Carl Zeiss Makro-Planar T2/50:
And these are the 49mm filters that we recommend for the Pentax 40mm F2.8 L:
Lens Mounts
Both the Carl Zeiss Makro-Planar T2/50 and the Pentax 40mm F2.8 L 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.
Carl Zeiss Makro-Planar T2/50 is also available in Canon EF and Nikon F (FX) mounts.
Pentax 40mm F2.8 L is also available in Pentax KAF mount.
Focal Range
Carl Zeiss Makro-Planar T2/50 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.
On the other hand, the 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.