When I started putting Leica lenses on the Sony NEX-5, I assumed that just about any Leica lens was going to be a big step up from the Sony 16mm that comes with the camera (you can also get the camera with the 18-55 mm zoom). I was surprised to find image quality to be an approximate tossup between the 16mm Sony kit lens and the Tri-Elmar. The Leica 18 mm Super Elmar M acquits itself very well on the NEX-5. In fact that body, because of the antialiasing filter, is incapable of extracting all of the resolution that the lens can deliver.
Things are different when you’re comparing Leica lenses to the Sony 18-55 mm zoom. The Sony zoom is acceptable at 18mm, but things go downhill fast as you zoom in. You’ll get far better results with almost any fixed-focal-length Leica lens, and you’ll have excellent manual focusing, a good depth of field scale, and focal lengths and lens speeds not available with the Sony lenses. The longer Leica lenses, so problematical on the M9 because of focusing and framing difficulties, work great on the NEX-5 if the subject is static.
At the end of my experiments, I have the following specific advice:
If you’ve got a pile of Leica lenses and want to use them on a digital body, but the M9 (or even a used M8) is too rich for your blood, using them on the NEX-5 makes a lot of sense, providing you can stand the brain-dead Sony ergonomics. You’ll get good images at a bargain price.
If you want to shoot video and manually focus, Leica lenses are an excellent solution. Leica lenses are famous for their silky smooth, perfectly weighted focusing. They are as good in this regard as the Sony lenses are bad. However, I don’t think I would go out and buy Leica lenses for this application; I’d probably get an adapter to a line of lenses that is not so outrageously expensive.
If you want a more pocketable backup to your M9, the NEX-5 will fill the bill. Remember the 1.5 X multiplier when selecting lenses.
If you’re working with relatively static subjects and are frustrated by the focusing accuracy you’re getting with your M9, using live view to focus the NEX-5 will be pure joy. If you routinely use lenses longer than 50 mm, run, do not walk, to your camera dealer and buy the Sony.
If you have an NEX-5, and don’t have the Sony 16mm lens, get one. It’s small, light, and remarkably good. While you’re at it, get the auxiliary finder; it’s not very accurate – showing a smaller area than you’ll see captured by the camera – but it works in bright light and allows steadier and more natural framing than holding the camera at arm’s length.
If you have no Leica lenses and are thinking of buying some to use on your NEX-5, save your money. Some of them are great, and all of them are at least pretty good, but the price/performance ratio is out of line. If you must upgrade your NEX-5 glass, consider instead the Zeiss or Voigtlander M-series lenses.