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 II ASPH for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is an important deciding factor when comparing two lenses. Panasonic 9mm F1.7 ASPH is the longer of the two lenses at 52mm. The Panasonic 20mm F1.7 II ASPH with a length of 26mm, is 26mm shorter. On the other hand, the Panasonic 20mm F1.7 II ASPH has a larger diameter of 63mm compared to the Panasonic 9mm F1.7 ASPH's 61mm diameter.
The weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Panasonic 20mm F1.7 II ASPH weighs 87g, 33% (43g) 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 Prime Lenses in Micro Four Thirds Mount for Size Comparison
Lens Mounts
Both the Panasonic 9mm F1.7 ASPH and the Panasonic 20mm F1.7 II 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-5, Panasonic GH6 and OM System OM-1.
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. Panasonic 20mm F1.7 II 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.