Lenstip tested the Olympus 12-100mm PRO lens and conlcudes:
To be honest the Olympus 12-100 mm surprised me very positively. I didn’t expect such good results. I was almost sure that at least for one focal length the image quality would be weak on the edges of the frame and the lens would fail in the category of flares as well. No such things happened and for that the constructors deserve a round of applause. You get a lens with a very wide range of focal lengths, a decent constant aperture fastness, one able to provide good quality images at every combination of aperture and focal length; additionally its autofocus is efficient and its optical stabilization performs very well indeed. Really, it would be difficult to demand anything more. Good job!