The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Olympus 25mm F1.2 Pro and the Panasonic 42.5mm F1.7 OIS 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. Olympus 25mm F1.2 Pro is the longer of the two lenses at 87mm. The Panasonic 42.5mm F1.7 OIS with a length of 50mm, is 37mm shorter. Besides being longer, the Olympus 25mm F1.2 Pro also has a larger diameter of 70mm compared to the Panasonic 42.5mm F1.7 OIS's 55mm 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 42.5mm F1.7 OIS weighs 130g, 68% (280g) lighter than the Olympus 25mm F1.2 Pro's weight of 410g.
Below you can find the dimension and weight table of the Standard Prime Lenses in Micro Four Thirds Mount for size comparison purposes.
Standard Prime Lenses in Micro Four Thirds Mount for Size Comparison
Lens Mounts
Both the Olympus 25mm F1.2 Pro and the Panasonic 42.5mm F1.7 OIS 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
Olympus 25mm F1.2 Pro is a prime lens with fixed focal lenght of 25mm which has an effective (full-frame 35mm equivalent) focal range of 50mm when used on a FourThirds format camera. Panasonic 42.5mm F1.7 OIS is a prime lens with fixed focal lenght of 43mm which has an effective (full-frame 35mm equivalent) focal range of 86mm when used on a FourThirds format camera.