The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Leica APO-Summicron-M 35mm F2 ASPH and the Leica Elmarit-M 21mm f2.8 ASPH 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. Leica Elmarit-M 21mm f2.8 ASPH is the longer of the two lenses at 46mm. The Leica APO-Summicron-M 35mm F2 ASPH with a length of 41mm, is 5mm shorter. Besides being longer, the Leica Elmarit-M 21mm f2.8 ASPH also has a larger diameter of 58mm compared to the Leica APO-Summicron-M 35mm F2 ASPH's 53mm 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. Leica Elmarit-M 21mm f2.8 ASPH weighs 300g, 6% (20g) lighter than the Leica APO-Summicron-M 35mm F2 ASPH's weight of 320g.
Below you can find the dimension and weight table of the Wideangle Prime Lenses in Leica M Mount for size comparison purposes.
Wideangle Lenses in Leica M Mount for Size Comparison
Filter Threads
The Leica APO-Summicron-M 35mm F2 ASPH has a filter size of 39mm whereas the Leica Elmarit-M 21mm f2.8 ASPH has a 55mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 39mm filters that we recommend you to consider for the Leica APO-Summicron-M 35mm F2 ASPH:
And these are the 55mm filters that we recommend for the Leica Elmarit-M 21mm f2.8 ASPH:
Lens Mounts
Both the Leica APO-Summicron-M 35mm F2 ASPH and the Leica Elmarit-M 21mm f2.8 ASPH has the same Leica M lens mount. Some of the latest released cameras that are compatible with the Leica M lenses are Leica M11 Monochrome, Leica M11 and Leica M10.
Focal Range
Leica APO-Summicron-M 35mm F2 ASPH is a prime lens with fixed focal lenght of 35mm.
On the other hand, the Leica Elmarit-M 21mm f2.8 ASPH is a prime lens with fixed focal lenght of 21mm.