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 Panasonic 20mm F1.7 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. Panasonic 9mm F1.7 ASPH is the longer of the two lenses at 52mm. The Panasonic 20mm F1.7 ASPH with a length of 26mm, is 26mm shorter. On the other hand, the Panasonic 20mm F1.7 ASPH has a larger diameter of 63mm compared to the Panasonic 9mm F1.7 ASPH's 61mm 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. Panasonic 20mm F1.7 ASPH weighs 100g, 23% (30g) lighter than the Panasonic 9mm F1.7 ASPH's weight of 130g.
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 Panasonic 20mm F1.7 ASPH has a 46mm 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 46mm filters that we recommend for the Panasonic 20mm F1.7 ASPH:
Lens Mounts
Both the Panasonic 9mm F1.7 ASPH and the Panasonic 20mm F1.7 ASPH 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.
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 Panasonic 20mm F1.7 ASPH is a prime lens with fixed focal lenght of 20mm which has an effective (full-frame 35mm equivalent) focal range of 40mm when used on a FourThirds format camera.