The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Panasonic 9mm F1.7 ASPH and the Samyang 21mm F1.4 ED AS UMC CS 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. Samyang 21mm F1.4 ED AS UMC CS is the longer of the two lenses at 68mm. The Panasonic 9mm F1.7 ASPH with a length of 52mm, is 16mm shorter. Besides being longer, the Samyang 21mm F1.4 ED AS UMC CS also has a larger diameter of 64mm compared to the Panasonic 9mm F1.7 ASPH's 61mm diameter.
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Below you can find a scaled side-by-side image of Panasonic 9mm F1.7 ASPH and Samyang 21mm F1.4 ED AS UMC CS to get a better idea of how their sizes compare in real life.
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. Panasonic 9mm F1.7 ASPH weighs 130g, which means it is 145g (52%) lighter than the Samyang 21mm F1.4 ED AS UMC CS which has a weight of 275g.
Below you can find the dimension and weight table of the Wideangle Prime Lenses in Micro Four Thirds Mount for size comparison purposes.
Wideangle Lenses in Micro Four Thirds Mount for Size Comparison
Filter Threads
The Panasonic 9mm F1.7 ASPH has a filter size of 55mm whereas the Samyang 21mm F1.4 ED AS UMC CS has a 58mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 55mm filters that we recommend you to consider for the Panasonic 9mm F1.7 ASPH:
And these are the 58mm filters that we recommend for the Samyang 21mm F1.4 ED AS UMC CS:
Lens Mounts
Both the Panasonic 9mm F1.7 ASPH and the Samyang 21mm F1.4 ED AS UMC CS has the same Micro Four Thirds lens mount. Some of the latest released cameras that are compatible with the Micro Four Thirds lenses are OM System OM-1 II, Panasonic G9 II and OM System OM-5.
Samyang 21mm F1.4 ED AS UMC CS is also available in Canon EF-M , Fujifilm X and Sony E mounts.
Focal Range
Panasonic 9mm F1.7 ASPH is a prime lens with fixed focal lenght of 9mm which has an effective (full-frame 35mm equivalent) focal range of
18mm when used on a FourThirds format camera.
On the other hand, the Samyang 21mm F1.4 ED AS UMC CS is a prime lens with fixed focal lenght of 21mm which has an effective (full-frame 35mm equivalent) focal range of 42mm when used on a APS-C / DX format camera.