The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Olympus M 25mm F1.8 and the Sigma 30mm F2.8 DN for their suitability to various photography scenarios:
Size and Weight Comparison
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. Sigma 30mm F2.8 DN weighs 135g, 0% (1g) lighter than the Olympus M 25mm F1.8's weight of 136g.
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
Lens Mounts
Both the Olympus M 25mm F1.8 and the Sigma 30mm F2.8 DN 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 30mm F2.8 DN is also available in Sony E mount.
Focal Range
Olympus M 25mm F1.8 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.
On the other hand, the Sigma 30mm F2.8 DN is a prime lens with fixed focal lenght of 30mm which has an effective (full-frame 35mm equivalent) focal range of 45mm when used on a APS-C / DX format camera.