Pentax-M SMC 135 f3.5
[USED ON A SONY NEX-5N FOR THIS TEST]
These old Pentax lenses are real gems when you can find one in good condition. If you are looking to buying these on the market right now (especially on ebay), you will have noticed how the price has been increasing steadily over the past months. The reason of course is the ability to use these on the CSC cameras via an adapter. The Pentax lenses, in particular the SMC lenses have become quite expensive. I was lucky, I bought a few of these lenses at very reasonable prices. I wouldn't get them for what I paid for them today.
The SMC Pentax-M 135mm f3.5 is very compact and is made of metal. Although only some 7cm long and 5cm in diameter, you can feel the weight when mounted on one of the small CSC cameras. Especially when mounted on an adapter the whole thing comes to around 10cm in length.
This was tested on a Sony Nex-5N camera with an EVF attached. It should be easier to focus with the peeking function that these cameras boast and it is. However, you still have to be careful about focusing, as it can be misleading as to where is actually in focus. I missed a few on this outing as I thought the subject was in focus but wasn't. Practice makes perfect and it should become easier with time.
Performance was good as long as the sun wasn't anywhere near the the lens opening. If the angle of the sun is quite small then contrast reduces by quite a bit and the colours become washed. You can bring it back in post processing to some degree but not all. I was astonished at the images when he sun was at my back and colour and contrast was excellent. Even wide open the rendition of the lens is very good. Some would even say it has something on that Leica lens feeling, and it does to some degree.
All in all, a very useful lens to have as primes of this focal length are missing at present and these old manual lenses are the only alternative. I'm very pleased to have this lens and I'm sure will get a lot of use in the future.