Every now and again I love to bust out my old M42 lenses and throw them on my Nikon. These old lenses have great image quality, are sharp as hell, and are loaded with personality. Beyond their attributes they tend to be very inexpensive as well
To get these lenses to work with any DSLR camera all you need is an adapter ring. I got mine for about twenty dollars on eBay. There are a few different versions of the M42 lens adapters. The one that I picked up is the most simple version. It is one machined piece of metal with a Nikon F mount on one side and then a threaded 42mm female thread in the front center of the adapter ring.
There is only one issue with this set up and that is some of the lenses cannot focus as close as they were designed to on film camera. To overcome this I bought a set of three macro ring adapters. They work by putting the lens farther away from the sensor and increase the minimum focus distance. This works brilliantly and as they are only machined aluminum they too cost next to nothing on eBay.
Most newer higher end cameras will allow you to place manual focus lenses onto their bodies with an appropriate adapter. You will control the aperture manually but most camera functions will work without a problem. On my Nikon cameras TTL will also function with out any problems.
The focus lock light will also work with this set up on most higher end Nikon camera. It is incredibly helpful to make sure that you have your focus correct and as sharp as possible. Just make sure that you check your camera's manual to make sure that it is a supported function with manual focus lenses mounted.
Using macro extension rings with your M42 lenses will allow you to get into macro photography with out the cost of buying a macro lens. Just make sure that you have a good sturdy tripod to keep everything steady. This situation would also benefit by using your camera timer to trip the shutter or any other method of remote triggering your shutter.
By using some old M42 screw mount manual focus lenses on your DSLR you will have a very inexpensive way to freshen up the way that you shoot and have more lens options in your bag.