dipo 1 here again, I use my old m42 lenses a lot on my K5, when I was using my old spotmatic I purchased a Vivitar Automatic Tele Converter m42 mount both ends. Seems to me I should be able to use this, (adapted of course) on the K5. Question is will it effect picture quality, etc. Any and all help greatly appreciated, good or bad. Also, I know I can play with it, just wanted to know what the pros have to say. Thanks.
The M42 tele-converter should work on the K5, with an M42 lens and suitable K-mount adapter. In terms of image quality, that will depend on the quality of the optics in the tele-converter. It may we worth an experiment to see if a an image with the tele-converter looks better (or worse) than a cropped image using just the same lens. You may well loose some contrast, etc. with the tele-converter but you may be able to recover some of that in post processing. The tele-converter will also loose you two stops of light (bare that in mind) and in some case can throw off the metering in the camera (exposure compensation may be needed). Interested to see what you find?