Do you remember Tamron’s Adaptall system of manual focus lenses? You would buy a lens and the appropriate adapter to make it fit your brand of camera. If you bought a different brand of camera, you could just buy an adapter/mount for the new one and you could still use your lenses. Now that was flexibility!
Being able to use older 35 mm lenses on the newer DX and FX bodies is another way to keep that favorite glass close by in your camera bag. With film still not dead (reports of its death have been greatly exaggerated, but that is a topic for another day and another post), having lenses that fit both a digital and a film body can make for great creative photographic possibilities.
When I was looking around for a new camera system to replace my Pentax Spotmatic F in the late 1980’s, my research led me to Nikon. Being a practical person, I wanted a system that had growth potential. The older lenses (with a few exceptions) were compatible with the newer bodies, that was a big selling point.
Even with the crop factor involved with using full frame lenses on the cropped sensor bodies, which as Paul C. pointed out in a recent focus session, that difference can give you an increased telephoto and magnification capability when it counts.
Even with my DSLRs (both DX and FX), I still have and use the same lenses I have had for years. After more than 20 years experience in the used photographic equipment business, my equipment roster has some great MF lenses. My Nikkor 300/4.5 IF-ED lens works well with my digital cameras, as does my Micro 55/2.8. My old Nikkor 35/3.5 PC lens was a favorite focal length when I was shooting 35 mm and my Nikkor 24/2 is the equivalent of 36 mm on my APS-C cameras.
So you can imagine my surprise and delight to find that the same MF lenses I use so often could be used with an adapter on a mirrorless camera. With a wide selection of adapters available today, you can mix and match an amazing number of cameras and lenses between brands. Most of the adapters are available for mirrorless camera bodies (with some available for DSLR’s) but the range of lenses are endless—Leica, Nikon, Canon, etc—both old and new. Have an R or M Leica lens you would like to use on that Olympus, Sony or Fuji? There is an adapter for that!
My everyday camera these days is a Sony NEX-7. It has been a great choice for my needs because I can use the 16-50 Sony lens or put on my Kiwi adapter and use any of my Nikkor lenses. I have to use them in aperture priority or manual, but that is fine with me. Having manual control of my camera has always been part of my photography, both analog and digital. My Tamron SP 35-80 was a constant on my D70s and the results have always been tack sharp. It is easier than carrying around a DSLR and I am always ready for those spur of the moment photo opportunities that crop up during the day.