I have old 35mm lenses for my old Minolta camera. I'm going back to photography and getting an Olympus PEN E-PL1 (micro four thirds mount).
Can I use my old lenses on such a box or do they become completely useless? They were pretty expensive lenses, so why throw them away?
There are a number of adapters for Minolta MC/MD to Micro Four Thirds, like this one at Amazon. (If you are talking about Maxxum/Dynax lenses, then look for Sony Alpha to Micro Four Thirds adapters.) The lenses will be all-manual focus and aperture (no automatic stop-down), but you can use them. It's just going to be an old-timey sort of experience in the digital age.
Yes, it works, but you'll need to remember the crop factor. Micro 3/4 has a crop factor of two, so an old 50mm lens will feel like a 100mm lens. Look here for a good explanation: https://en.wikipedia.org/wiki/Crop_factor
There are a bunch of different factors, but yes, you can adapt both Minolta AF and Minolt MC/MD lenses to micro four-thirds--you can adapt practically every SLR mount to micro four-thirds with simple rings, and with an Olympus body you'll have stabilization as well.
But.
If they're Minolta AF lenses, you won't have an aperture ring on the lens by which to control the aperture setting--since the camera and body won't talk to each other. You also won't have autofocus. You won't have wide-open metering, but must rely on stopped-down metering. There's no EXIF information from the lens, and on top of all that the crop factor for four-thirds is 2x, so every lens you had on your Minolta camera will feel twice as long on an µ4/3 body (e.g., a 28mm lens is no longer wide angle, but slightly telephoto, as the field of view will be roughly the same as a 56mm lens).
All of which means that you might be better off either buying µ4/3 lenses, or (if your lenses are Minolta AF) getting a Sony A-mount body, as the A-mount is the Minolta AF mount.
And then there's the issue of how you're gonna focus. Olympus and Panasonic only came to the focus-peaking table late in the game. An older body, like an E-PL1 (new at the time of the post, but venerable in digital camera terms these days) doesn't have the type of manual focus aids that made an MD/MC lens usable on a Minolta body. You have no optical viewfinder--there's no focus screen with split circles or pentaprisms. And some bodies don't even sport an electronic viewfinder, so you have to judge focus from an LCD. Focus peaking and magnification patches can help, but it's far more convenient to use a modern digital-age autofocusing lens in the native mount. Not to mention µ4/3 lenses are a lot smaller and lighter and better fits overall with their bodies than adapted SLR lenses.
It's typically only going to be worth it if the lens is an exotic, pro-quality, and still useful with the new field of view.
