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 Sigma 30mm F2.8 EX DN 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. Olympus 25mm F1.2 Pro is the longer of the two lenses at 87mm. The Sigma 30mm F2.8 EX DN with a length of 39mm, is 48mm shorter. Besides being longer, the Olympus 25mm F1.2 Pro also has a larger diameter of 70mm compared to the Sigma 30mm F2.8 EX DN's 61mm 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. Sigma 30mm F2.8 EX DN weighs 135g, 67% (275g) 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 Lenses in Micro Four Thirds Mount for Size Comparison
Filter Threads
The Olympus 25mm F1.2 Pro has a filter size of 62mm whereas the Sigma 30mm F2.8 EX DN has a 46mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 62mm filters that we recommend you to consider for the Olympus 25mm F1.2 Pro:
And these are the 46mm filters that we recommend for the Sigma 30mm F2.8 EX DN:
Lens Mounts
Both the Olympus 25mm F1.2 Pro and the Sigma 30mm F2.8 EX 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 EX DN is also available in Sony E mount.
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.
On the other hand, the Sigma 30mm F2.8 EX 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.