When the target shows sharply, you're at the focal length, which is also the minimum focus distance. So, mount a lens on extension (tubes an/or bellows) on a camera, preferably one with LiveView. There is a much easier way to measure FL, based on this: A non-reversed lens cannot focus closer than its focal length. Neither Bob's easy nor hard ways are very usable nor straightforward. Super-Multi-Coated Bellows-TAKUMAR 1:4/100 Super-Multi-Coated Fisheye-TAKUMAR 1:4/17 The trick using a camera lens will give the camera register distance instead of lens focal length. Visualopsins wrote: Note the FL trick works for enlarger lenses and projection lenses, but not for camera lenses. The simple truth is this: There are no neutral photographs. Too many film+digi cams+lenses, oh my - Pentax K20D, K-1000, M42s, more I hold a ruler next to the lens to measure the distance from the target surface. I do this under a ceiling fluorescent tube when the projected edges are sharp, that's about the focal length. You know the focal-length trick, right? Hold the lens under a light over a flat white surface and see where the lens focuses. Posted: Wed 1:31 am Post subject: Re: 10cm diameter vintage magic lantern lens. Location: California or Guatemala or somewhere I don't care who designed it, who made it or what country it comes from - I just enjoy using it! In good condition with only one tiny piece of fungus right at the edge and no scrathes or marks, just a tiny bit of dust.ĪNyone go any idea what king of focal length this might be and what kind of maximum focus distance might I get if I mount it on my EOS 10D?
The front and rear elements are both very convex and symmetrical, no idea what design this has, it is very distorted and very wide angle. This is a huge and heavy 10cm diamter lens from a magic lantern projector. Posted: Tue 11:53 pm Post subject: 10cm diameter vintage magic lantern lens.
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