The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Olympus M 45mm f1.8 and the Panasonic Leica 42.5mm F1.2 OIS 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 Leica 42.5mm F1.2 OIS is the longer of the two lenses at 77mm. The Olympus M 45mm f1.8 with a length of 46mm, is 31mm shorter. Besides being longer, the Panasonic Leica 42.5mm F1.2 OIS also has a larger diameter of 74mm compared to the Olympus M 45mm f1.8's 56mm 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. Olympus M 45mm f1.8 weighs 116g, which means it is 309g (72%) lighter than the Panasonic Leica 42.5mm F1.2 OIS which has a weight of 425g.
Below you can find the dimension and weight table of the Telephoto Prime Lenses in Micro Four Thirds Mount for size comparison purposes.
Telephoto Lenses in Micro Four Thirds Mount for Size Comparison
Filter Threads
The Olympus M 45mm f1.8 has a filter size of 37mm whereas the Panasonic Leica 42.5mm F1.2 OIS has a 67mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 37mm filters that we recommend you to consider for the Olympus M 45mm f1.8:
And these are the 67mm filters that we recommend for the Panasonic Leica 42.5mm F1.2 OIS:
Lens Mounts
Both the Olympus M 45mm f1.8 and the Panasonic Leica 42.5mm F1.2 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-1 II, Panasonic G9 II and OM System OM-5.
Focal Range
Olympus M 45mm f1.8 is a prime lens with fixed focal lenght of 45mm which has an effective (full-frame 35mm equivalent) focal range of
90mm when used on a FourThirds format camera.
On the other hand, the Panasonic Leica 42.5mm F1.2 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.