I bought a €20 lens adaptor for my ancient Pentax Takumar 85mm f1.8 lens today at the Mauerpark flea market in Berlin. Now I can use this great lens on my Sony NEX 7 & C3 cameras. On my way home I snapped a couple of pics. The 85mm lens has roughly a focal length of 130mm on the APS-C size sensor of the NEX cameras. I'm actually not a telephoto lens guy. However, I think, like with weather, there is no good or bad focal length. 

All images below where shot with the Sony NEX C3 mostly at wide open aperture, somewhere around f-stop 1.8 and 4. I like how you can be at some distance to your main subject but still isolate it from the background. Music track Calling Me by Charlie Winston