I have a 20mm security tv camera lens which is hands down my favorite micro four thirds lens. It has flare like you wouldn’t believe, and the aperture doesn’t even try to approximate a circle as you stop down, but indoors neither of these present real problems, and at 1.4 it lets you keep the iso way lower than the kit lens.
Anyways, I was intrigued by the idea of a fast zoom offered by some of the c-mount zoom lenses. The issue is that there is none or at least very little documentation telling you what sort of coverage you might get with these lenses. While I have only experimented with one lens it’s likely that the same would apply to other lenses of approximately the same focal length, 12.5-75mm. You’ll probably get better coverage with lenses that start at a slightly longer focal length, but some of these lenses are really quite large relative a micro four thirds camera, they’d probably look almost comically small and balance much better on an aps-c or full frame camera. They’ll probably be more comfortable on a dslr styled camera (think g-series) than a compact styled camera (think e-pm1, gx series). In fact the reason I chose the particular lens I did was that it was very small relative the other options.
The navitar 12.5-75mm DOZ-6X12.5, has an image circle of about 13mm (a little less at the wide end, a little more at the long end). If you crop to minimize vignetting you get a little more than half the resolution out of your sensor at the wide end, and more than that at the long end. Nothing is as valuable as examples, so I put some uncropped and cropped images up here. I would only really look at the coverage, because I wasn’t shooting at reasonable apertures and there’s no guarantee I nailed focus on these photos. But it’s slightly more interesting than shooting newsprint.
Because of the vignetting these make great toys, but I’m still not sure how frequently I’m going to grab it when going out. Also, I think its motivated me to add a grip to my e-pm1, because it really is easier & more comfortable to hold the camera steady with something on there.