The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Olympus ED 100-400mm F5.0-6.3 IS and the Olympus ED 75-300mm f4.8-6.7 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 100-400mm F5.0-6.3 IS is the longer of the two lenses at 206mm. The Olympus ED 75-300mm f4.8-6.7 with a length of 116mm, is 90mm shorter. Besides being longer, the Olympus ED 100-400mm F5.0-6.3 IS also has a larger diameter of 86mm compared to the Olympus ED 75-300mm f4.8-6.7's 70mm 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 ED 75-300mm f4.8-6.7 weighs 430g, 61% (690g) lighter than the Olympus ED 100-400mm F5.0-6.3 IS's weight of 1120g.
Below you can find the dimension and weight table of the Telephoto Zoom Lenses in Micro Four Thirds Mount for size comparison purposes.
Super Telephoto Lenses in Micro Four Thirds Mount for Size Comparison
Filter Threads
The Olympus ED 100-400mm F5.0-6.3 IS has a filter size of 72mm whereas the Olympus ED 75-300mm f4.8-6.7 has a 58mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 72mm filters that we recommend you to consider for the Olympus ED 100-400mm F5.0-6.3 IS:
And these are the 58mm filters that we recommend for the Olympus ED 75-300mm f4.8-6.7:
Lens Mounts
Both the Olympus ED 100-400mm F5.0-6.3 IS and the Olympus ED 75-300mm f4.8-6.7 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 100-400mm F5.0-6.3 IS has a focal range of 100-400mm and
4.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
200-800mm when used on a FourThirds format camera.
On the other hand, the Olympus ED 75-300mm f4.8-6.7 has a focal range of 75-300mm and 4.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 150-600mm when used on a FourThirds format camera.