Sony makes two A-mount to E-mount adapters for the NEX line:
- The LA-EA1 is a basic adapter that passes the lens information to the camera. It supports autofocus via the usual contrast detect method the NEX line uses as well as aperture control for exposure (again via the camera's controls). It has a small detachable tripod foot and sells for US$200.
- The newer and fancier LA-EA2 is a bigger, more complex adapter. Besides the basic things in the LA-EA1, the LA-EA2 adds a translucent mirror and a 15-point phase detect autofocus system (3 cross sensors), for DSLR-like focus performance on the NEX bodies. The benefit is fast autofocus and better autofocus tracking. The drawback is that the adapter is a bit larger and more cumbersome (it has a permanent tripod foot) and the adapter draws power from the camera. That last bit is something you want to be aware of. The LA-EA2 draws down your battery far faster than without it. US$400.
Thom's Comments: I've been using a number of Alpha-mount primes on my NEX-5 and enjoying that. With care in choosing which lens you adapt, you can get excellent, fast aperture normal-to-telelphoto options that don't exist in the NEX lens lineup yet. For example, the 50mm f/1.4 lens makes a decent portrait lens for the NEX without too much bulk, at least until the E-mount 50mm f/1.8 appears. I've also got an older 35mm f/1.4 that makes a nice "normal" lens when adapted to my NEX. I would tend to avoid big, complex zooms via the adapter. First, if you're using the LA-EA1 you want fast lenses so that the contrast-detect autofocus system is getting plenty of light. Second, the small size of the NEX body really cries out for smaller lenses.