A very cheap manual focus tele zoom, relatively easy to find. And it has a constant aperture of f/4. In a sense, it's an ancestor of the Nikkor AF 70-210 f/4. Is it a bargain? You obviously lose the autofocus, but it's also significantly cheaper. I bought mine for only $22 (although it had a small scratch on the front element, which didn't affect performance).
+ a very cheap tele lens with constant aperture
+ superb image quality
+ very smooth focus, and excellent ergonomics overall
- manual focus means no fast moving subjects (unless in panning?)
- like with all AIS lenses, entry-level cameras will not meter...
- ...and their small viewfinders make manual focusing a challenging task
|Absolutely no complaints about image quality. It's superb|
- landscapes. It's flexible, it's optically great, and it allows for precision focus (with bright viewfinders)
- constant aperture f/4 + good image quality = good candidate for teleconverter
- 210mm and f/4 could make an interesting portrait lens for outdoor use.
- fast moving objects
- use with entry-level cameras. No metering and small viewfinders will make working with this lens a rather frustrating experience.
- if you can afford one of the autofocus lenses, they are probably better value
It's cheap, it's superb, and it's fast (f/4 @ 210mm is not bad at all). Being a zoom also means it's quite flexible, and I can see this lens being a great option for landscape photographers - especially those using a camera body that has a bright viewfinder and offers metering. Another highly intriguing application would be to get a cheap teleconverter, a micro 4/3 adapter, and use it with a mirrorless. You'd have a 140-420mm f/8 lens - and taking into consideration the 2x crop factor, you'd actually have a 280-840mm lens! Now, that's a pretty sweet deal, particularly considering that this lens gives you plenty of goodness with its image quality. All in all, I would definitely recommend this lens, especially if you have a camera that supports metering. If not, you could still give it a shot, but it will require patience and quite a lot of trial & error runs...