A few months ago, I bought a Tamron Adaptall 2 SP 500mm f/8 55BB mirror lens. Not that I needed it, but the price was so low that it would have been silly not to buy it. The lens came with a Nikon Adaptall adapter, so I tried it on my trusty Nikon D90 a couple of times. But since then, the lens has been sitting idly on a shelf.
Last weekend, though, the weather was (relatively) nice, there was some hectic bird activity in our garden, and I felt like doing something else than sitting in front of the computer all day long. So I’ve been monkeying around with the lens mounted on a SONY NEX-3N using an el cheapo FOTGA F-mount adapter.
This turned out to be an unwieldy yet surprisingly usable setup. Shooting with a rather hefty lens attached to a SONY NEX-3N proved to be a challenge. On the 1.5X crop sensor, the lens has a 750mm focal length, so focusing and keeping the camera stable, especially when shooting hand-held was far from an easy task. For better results, I switched to the Shutter Priority mode and cranked up the shutter speed to 1/800 sec.
Mirror (or catodioptric) lenses are more compact and much less expensive than proper tele lenses. There are also drawbacks: catodioptric lenses have a fixed aperture (f/8 in case of 55BB) and they produce unusual doughnut-shaped bokeh that can be distracting. Fixed f/8 aperture and long focal length mean that you need to shoot at high ISO in most situations. Fortunately, most modern cameras, including the lowly SONY NEX-3N, can handle high ISO rather well.
Mirror lenses rarely score high marks in optical quality tests (see, for example, a review by Photozone.de), but I found the results produced by the lens more than adequate. Sharpness is acceptable, there is no noticeable vignetting, distortion is negligible, and there is no color fringing to speak of. What’s not to like?
Tamron Adaptall 2 SP 500mm f/8 55BB is compatible with the SP 1.4X Tele-Converter which increases the focal length to 1050mm on a 1.5x crop sensor. I happen to have the tele-converter too, so it looks like I have another photography project for a sunny weekend.