The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Olympus ED 12-40mm f2.8 PRO and the Olympus M 14-42mm f3.5-5.6 II R 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 ED 12-40mm f2.8 PRO is the longer of the two lenses at 84mm. The Olympus M 14-42mm f3.5-5.6 II R with a length of 50mm, is 34mm shorter. Besides being longer, the Olympus ED 12-40mm f2.8 PRO also has a larger diameter of 70mm compared to the Olympus M 14-42mm f3.5-5.6 II R's 57mm 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 14-42mm f3.5-5.6 II R weighs 112g, 70% (270g) lighter than the Olympus ED 12-40mm f2.8 PRO's weight of 382g.
Below you can find the dimension and weight table of the Standard Zoom Lenses in Micro Four Thirds Mount for size comparison purposes.
Standard Lenses in Micro Four Thirds Mount for Size Comparison
Filter Threads
The Olympus ED 12-40mm f2.8 PRO has a filter size of 62mm whereas the Olympus M 14-42mm f3.5-5.6 II R has a 37mm 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 ED 12-40mm f2.8 PRO:
And these are the 37mm filters that we recommend for the Olympus M 14-42mm f3.5-5.6 II R:
Lens Mounts
Both the Olympus ED 12-40mm f2.8 PRO and the Olympus M 14-42mm f3.5-5.6 II R 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 ED 12-40mm f2.8 PRO has a focal range of 12-40mm and
3.3X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
24-80mm when used on a FourThirds format camera.
On the other hand, the Olympus M 14-42mm f3.5-5.6 II R has a focal range of 14-42mm and 3.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 28-84mm when used on a FourThirds format camera.