The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Carl Zeiss Planar T1,4/50 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 Planar T1,4/50 is the longer of the two lenses at 69mm. The Pentax 40mm F2.8 L with a length of 15mm, is 54mm shorter. Besides being longer, the Carl Zeiss Planar T1,4/50 also has a larger diameter of 66mm 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, 77% (270g) lighter than the Carl Zeiss Planar T1,4/50's weight of 350g.
Below you can find the dimension and weight table of the Standard Prime Lenses in Pentax KAF Mount for size comparison purposes.
Standard Lenses in Pentax KAF Mount for Size Comparison
Filter Threads
The Carl Zeiss Planar T1,4/50 has a filter size of 58mm 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 58mm filters that we recommend you to consider for the Carl Zeiss Planar T1,4/50:
And these are the 49mm filters that we recommend for the Pentax 40mm F2.8 L:
Lens Mounts
Both the Carl Zeiss Planar T1,4/50 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 Planar T1,4/50 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 Planar T1,4/50 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.