I don't really know what to make of this. I've had an Olympus tcon 17 (1.7x screw on front teleconverter) since my Olympus C2040Z and used it on a variety of digicams and DSLR lenses with varying success. Often it was difficult to see any improvement over the un-converted lens uprezzed by 170%, sometimes there was fringing or reduced contrast. I recently tested on Panasonic 45-150 and 45-200 and wasn't too impressed. Anyway, the arrival of my EM1 and 12-50 prompted another trial, particularly as the lens is internally focussed so no strain on a wobbly extended barrel. (tcon 17 is heavy). In use the setup is held with left hand supporting the t/c. The diptych above shows on the left a 100% crop of the image from the lens fully zoomed at 50mm and uprezzed by 170% to match the right hand image which is the lens at 50mm with the tcon17 added via a 52-55 step up ring. No question which has more detail but freakily the tcon17 looks more contrasty (or is it just the extra detail?). The only PP was a slight removal of CA on the tcon17 image, an attempt to sharpen the LHS didn't improve matters. I did two tests of different subjects and the result was the same. Also there is none of the loss of a stop which occurs if a rear mounted t/c is used. (I checked this with consecutive exposures of a cloudless sky). I will be very interested to see how this combination compares with the 45-150 and 45-200. Certainly it has the advantage of a limited range power zoom before vignetting starts. I haven't tested the 12-50's macro with it.