Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Panasonic 12-60mm F3.5-5.6 is the longer of the two lenses at 71mm. The Olympus ED 12-45mm F4 Pro with a length of 70mm is 1mm shorter. Besides being longer, the Panasonic 12-60mm F3.5-5.6 also has a larger diameter of 66mm compared to Olympus ED 12-45mm F4 Pro's 63mm diameter.
Weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Panasonic 12-60mm F3.5-5.6 weighs 210g, 20% (44g) lighter than the Olympus ED 12-45mm F4 Pro's weight of 254g.
Below you can find the dimension and weight table of the 'Standard Zoom Lenses in Micro Four Thirds Mount for size comparison purposes.
Standard Zoom Lenses in Micro Four Thirds Mount for Size Comparison
Lens Mounts
Both Olympus ED 12-45mm F4 Pro and Panasonic 12-60mm F3.5-5.6 has the same Micro Four Thirds lens mount. Some of the latest released cameras that are compatible with the Micro Four Thirds lenses are Panasonic GH6, OM System OM-1 and Panasonic GH5 II.
Focal Range
Olympus ED 12-45mm F4 Pro has a focal range of 24-90mm and 3.8X zoom ratio which has a 35mm equivalent focal range of 48-180mm when used on a FourThirds format camera. Panasonic 12-60mm F3.5-5.6 has a focal range of 12-60mm and 5.0X zoom ratio which has a 35mm equivalent focal range of 24-120mm when used on a FourThirds format camera.