I made another Thrift Store purchase yesterday. For $20 I got a Cosina 50mm f1.4 Manual Focus K-Mount lens, complete with a hopelessly broken Cosina CT-1 camera. The whole rig is cheap plastic, which Cosina was known for in the 1980's, but the price was right, especially for a lens as fast as this. For Newbies, "fast" means it has a very wide Aperture, represented by a low numeric value. For instance, my fastest 50mm before this purchase is a Pentax Takumar with f 2. This one is f 1.4. Typically, a lens with a maximum aperture of f 1.4 is almost as good as it gets, although in the Leica Rangefinder world, there are some f 1.2, and even a f 0.95, which is absolutely a big as it gets. But you never pick up this kind of thing in a Thrift Store for $20. These would sell for $2000 if you're lucky.
Alright, so this is a Cosina plastic bodied lens, not highly regarded. But how does it perform? I would expect it has Multi-Coated glass optics, and indeed it is marked "MC" on the front - so that's gotta be good.
I snapped a few cat photos this morning with the aperture wide open. Of course there's no auto-focus, but I do have a "chippped" K-Mount to EOS Aapter, which means there is electronic communication with the camera body for exposure and focus. It provides automatic exposure for Aperture and Shutter Priority shooting, and more importantly, it enables the focus sensor, so that as you're manually turning the focus ring, the camera will beep and show the green focus dot, as well as the red cross-hairs in the Canon EOS camera viewfinder. This set-up, with "chipped" lens adapters works with ALL Canon EOS cameras, both film and digital. It's fantastic to have, and once you get confident with it, I would say that focus can be achieved manually almost as quickly as you can get Auto-Focus.
With cats, you have to be fast, and with "Merlin" above, one focus point lit up just ahead of his upper ear. As you can see, that zone of the picture is sharp, and the rest of it is soft. But I'm happy enough with it.
For Newbies again - recall that the bigger your Aperture setting (smaller numeric value), the less of the picture will be in focus from back to front, especially at close range. I could've gotten Merlin's whole head in focus by stopping the Aperture down to f4, but this was intended as more of a lens test to see what this lens looks like wide open - and it is quite good. Here are a couple of other cats:
Conclusion - Focus is a bit soft overall, but this is true of any lens when used wide open. I'm looking forward to trying some night-time street shooting with this lens - that's what it's made for.