Many old analog lenses can fit in DSLR cameras with proper adapter (although some lenses have problem with focusing at infinity).
[img=500x333]http://i.imgur.com/9Am69.jpg[/img]
In Mirrorless cameras, the compatibility is better (due to the shorter flange focal distance).
[img=500x333]http://i.imgur.com/Kkoz0.jpg[/img]
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The +
[li]Most old lenses are cheap[/li]
[li]Some are real gems, esp. the primes[/li]
The -
[li]Things need to be done manually (focus, aperture)[/li]
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As far as I know [url=http://en.wikipedia.org/wiki/M42_lens_mount]M42[/url] is the most popular lens mount (due to simplicity and a large selection of lenses), with Takumar being one of the most sought after lenses (due to it's good reputation among users). Many German and Russian lenses also come in M42 mount.
[img=500x333]http://i.imgur.com/dxRnC.jpg[/img]
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Manual lenses are fun to use!
50mm 1:1.4 lenses are my favorite, I think they give the best value for money. Up there in the banner is my current setup (1 kit lens + analog lenses).
Have any of you guys tried the digital body + analog lens combination?