These are just a couple of quick handheld test shots from a short walk with my new Zenitar 16mm. I got the M42 version brand new for a ridiculously cheap £60 GBP. For that price I wasn't expecting much, but I'm actually very pleasantly surprised.
It turned out that all those horror stories about the condition the Zenitar arrives in from the factory are true. The lens was awful straight out of the box, and I had to spend two evenings tweaking and adjusting to get it right. I made the following modifications:
Permanently converted to K mount.
Partially disassembled the lens to clean out all the crud and dust left over from manufacturing.
Adjusted to achieve infinity focus, which was set incorrectly by the factory.
Tested with and without the factory-fitted clear rear filter. Found contrast and sharpness much better without it. Adjusted infinity focus again to work without the filter.
Adjusted the aperture ring so that the actual light coming through the diaphragm matches the f-stop marked on the lens. It was out by a whole stop.
Attached a metal hood. Had to attach it permanently, as there is no filter ring.
And now that it's finally working properly, I love it. It's the best value for money I've ever had from a new lens by miles. The only processing on the test shots above is to set black and white points, defish using the PT Lens plug-in, and a very light sharpen. Properly adjusted, the Zenitar is so sharp that very little post-capture sharpening is needed. But I can only recommend it if you don't mind doing some work with a set of screwdrivers first.