Today I scored a long lens. 400 mm 6.3 m42 ( around 600mm on a crop body ?) I have whacked it on the camera and had a quick play.....now I need some tips? hints ? on how to use it. It is an early preset with the 2 aperture rings.....I have googled it but its not making much sense ....I set the front aperture ring to one f-stop and then the back one to another? How do I know which to set to what? and why?
and is there some way to tighten up the tripod collar? It seems to be all in one piece but it rotates around the lens
So if anyone can explain the basics to me I would be eternally grateful