Originally posted by Darley Thanks Boris don't like the sound of that! I see some genuine Pentax ones but there seem to be different types of these, or is it just some are a newer design? What's this about locking pins on some M42 lenses - are there different adapters for these or do I need to remove the pins or what?
There are a couple of things to note her for new M42 users.
SMC takumars and some super tak's (I think) were made for the latest spot antics which featured open aperture metering. There is a small pin in the mount that needs to be depressed to change aperture.
There is also the aperture activation pin, where some people have noted that this pin needs to be depressed to stop the lens down, and they lack the A/M switch.
There are third party adaptors which can depress this pin, otherwise you are into modifying the lenses, it is a simple reversible mod, but some prefer not to do it.
The risk with third party adaptors, as others have suggested is quality. Check for the retaining spring for binding into the lens base, the screw holding the spring being too long, and for machining swarf being left on the adaptors. Once properly inspected and all issues addressed they are fine