If you have access to a high resolution 3D printer, you can print your own M42 to EOS lens adapter. If printed exactly, it can assure focus to infinity. http://www.thingiverse.com/thing:2200432
That looks very cool, but I have to wonder why anyone would do it when you can get metal ones dirt cheap. I'm seeing prices from 99p (about $1.25) upwards from Chinese sources, £3.38 and up with an AF confirm chip. Given the option I think most people would prefer the metal, for one thing it isn't going to be damaged so easily as the plastic.
Agree. But it is a quick solution for ones that have a 3D printer at hand. Plus, it is a good exercise if they intend to print their own film camera. It is not easy to achieve such a good accuracy... you need a good printer and at least PLA material. Anyway, it won't hurt your camera as a badly executed metal adapter. BTW, the flange of the prize camera (SL1) is not entirely of metal, there is only a metal ring where the lens touches the body, those internal "wings" that should retain the lens inside are from plastic. This is really bad.
That's a good point. I hadn't thought about the material of the camera body. What prompted my comment is that I often see things like this where someone has put together a really cool project for 3D printers - and usually it winds up being much more expensive than just buying the thing you want. For example, someone did instructions for an adapter for using an iPhone as a microscope camera. It cost about four pounds for the filament used by the printer plus about three pounds for some special nuts and bolts, bits of rubber, etc. that the guy who published the instructions was willing to sell to anyone that wanted them. Meanwhile the usual Chinese sources were selling them complete for a fiver...
Indeed 3D printing is still expensive. Although we can make our printer at home, we still depend on consumables that they (the industry) take care to be expensive.
3D printers aren't as expensive as they used to be. I have one that can print a lot of different plastics and I paid $250 USD for it. Materials are pretty cheap and easy to find too. We can get a 1kg roll of ABS plastic for $20 USD off of Amazon! The ones that are still expensive are the printers that can print real metal.
It's a technology I'd really love to get into, but every example I see is either easier to buy off the shelf (as above) or needs much higher resolution than the cheaper printers. Thinking about it, one thing that'd be very nice and is probably well within the limits of the lower end printers is a "lens in body cap" thing. You'd need to buy the glass, of course, and probably drill the aperture stop(s), but the rest of it shouldn't be technically demanding.