Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.OM System 40-150mm F4.0 PRO is the longer of the two lenses at 99mm. The OM System 12-40mm F2.8 PRO II with a length of 84mm is 15mm shorter. On the other hand, the OM System 12-40mm F2.8 PRO II has a larger diameter of 70mm compared to OM System 40-150mm F4.0 PRO's 69mm diameter.
Below you can find the scaled side by side image of OM System 12-40mm F2.8 PRO II and OM System 40-150mm F4.0 PRO to get a better idea of how their size compare in real life.
Comparison image of OM System 12-40mm F2.8 PRO II and OM System 40-150mm F4.0 PRO Size and Weight 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.
Lens Mounts
Both OM System 12-40mm F2.8 PRO II and OM System 40-150mm F4.0 PRO 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
OM System 12-40mm F2.8 PRO II has a focal range of 12-40mm and 3.3X zoom ratio which has a 35mm equivalent focal range of 24-80mm when used on a FourThirds format camera. OM System 40-150mm F4.0 PRO has a focal range of 40-150mm and 3.8X zoom ratio which has a 35mm equivalent focal range of 80-300mm when used on a FourThirds format camera.