How to Do Everything!
An EOS D30, fitted with a 50mm Pentacon f/1.8 lens from the late 70s. As an alternative to expensive lenses, many people have fitted M42 (commonly called “Pentax screw thread”) lenses to their Canon DSLRs. M42 lenses are plentiful, and often very inexpensive in comparison to their more modern counterparts, as they were fit to a ton of ’60s and ’70s 35mm SLRs. Unlike other mountings, they have a flange focal depth very close to that of the EOS, which means you don’t lose the ability to focus to infinity.
These aren’t usually useful for sports photography that requires rapid focusing, for example, because they are almost without exception manually focused.[1] Nor are they particularly good for quick snapshots, since shots can take a little while to set up. But sometimes, economy is important, or you might happen have a bunch of M42 lenses sitting around. Maybe you just want to see what photographs old lenses will take. If so, then it may be worth your time to try using one with your EOS digital SLR. Here’s how.
Making a psi wheel can be an interesting demonstration of telekinesis or science, depending on your individual perspective. Unlike a psi ball, a psi wheel creates a readily observable effect that’ll have most people scratching their heads. This article will describe how to make and use one, followed up by some theories as to why putting your hand near a piece of paper can make it spin.
Read How To