The type of photography that you are planning to use is an important decision factor. Here we have evaluated the OM ED 20mm F1.4 Pro and the Sigma 56mm F1.4 DC DN C 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. OM ED 20mm F1.4 Pro is the longer of the two lenses at 62mm. The Sigma 56mm F1.4 DC DN C with a length of 60mm, is 2mm shorter. On the other hand, the Sigma 56mm F1.4 DC DN C has a larger diameter of 67mm compared to the OM ED 20mm F1.4 Pro's 63mm 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. OM ED 20mm F1.4 Pro weighs 247g, which means it is 33g (11%) lighter than the Sigma 56mm F1.4 DC DN C which has a weight of 280g.
Below you can find the dimension and weight table of the Standard Prime Lenses in Micro Four Thirds Mount for size comparison purposes.
Standard Lenses in Micro Four Thirds Mount for Size Comparison
Filter Threads
The OM ED 20mm F1.4 Pro has a filter size of 58mm whereas the Sigma 56mm F1.4 DC DN C has a 55mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 58mm filters that we recommend you to consider for the OM ED 20mm F1.4 Pro:
And these are the 55mm filters that we recommend for the Sigma 56mm F1.4 DC DN C:
Lens Mounts
Both the OM ED 20mm F1.4 Pro and the Sigma 56mm F1.4 DC DN C 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.
Sigma 56mm F1.4 DC DN C is also available in Sony E and Leica L mounts.
Focal Range
OM ED 20mm F1.4 Pro 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.
On the other hand, the Sigma 56mm F1.4 DC DN C is a prime lens with fixed focal lenght of 56mm which has an effective (full-frame 35mm equivalent) focal range of 112mm when used on a APS-C / DX format camera.