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Tuesday, August 3, 2010

Low-Cost Lens Solutions

Think about using a lens adapter to get lower-cost specialty lenses

Labels: GearLens Adapters

This Article Features Photo Zoom

You don’t get something for nothing, though, and in the case of lens adapters, there are some trade-offs of which to be aware. Here are some things to consider when choosing an adapter.

Can I Use This Lens On This Camera?
Whether you can use a given lens on a given camera body depends on several things. First, an appropriate adapter must be available. Second, the flange back distance must be compatible. Third, the lens must not physically interfere with the DSLR’s mirror, which swings up and down. Fourth, the lens should cover the camera format.

Adapters are available to mount a wide range of lenses on a wide range of bodies. See the Resources box for some sources (or do a web search for “A to B adapter,” where A is your camera body and B is the lens you wish to use with it).

The flange back distance is the distance between the lens mount and the image plane. If the lens was designed for a shorter distance than that of the camera body, the lens won’t focus out to infinity (although you can use it for close-up photography). There are adapters that contain glass elements to allow such lenses to focus out to infinity, but these also act as low-power teleconverters (they increase the focal length somewhat and reduce the effective aperture a bit), and the added elements can reduce sharpness and contrast. If the adapter isn’t thick enough, the flange back distance will be too short and the lens will focus beyond infinity. Since adapters—especially the lower-priced ones—tend to vary in precision, it’s a good idea to buy yours from a source that will allow you to return it if it doesn’t provide proper focusing.

Some lenses have designs that protrude into the camera body, either at all times or during focusing. These lenses shouldn’t be used on cameras where they’ll strike the DSLR mirror. It’s possible, with some cameras, to use such lenses with the mirror locked up, but you can’t see through the DSLR’s optical viewfinder with the mirror locked up to compose and focus, and you can damage the camera and lens should the mirror come back down with the lens attached, so it’s best to avoid such lens/camera combinations.

The new mirrorless interchangeable-lens cameras (Olympus PEN E-P1, E-PL1 and E-P2, Panasonic Lumix DMC-G2, G10, GF1 and GH1, Samsung NX10 and Sony Alpha NEX-3 and NEX-5) don’t contain SLR mirror boxes and thus have a very short flange back distance, so they can accept pretty much any lens for which an adapter can be found, and the lens-and-lens-adapter combination will be able to focus out to infinity.


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