Originally posted by bikehead90 Did you have to use an M42 —> K-mount adapter? If so any recommendations? I've been looking at them and seeing people say theirs have damaged the lens or the camera is off-putting.
My apologies, you did mention that in your original post and I forgot to comment on it.
Yes, it's an M42 mount and you'll need an M42-to-K-mount adapter.
You need to be wary of one thing, though...
With my copy of the lens, the diaphragm actuation pin (the metal pin sticking out from the rear) was unusually long, and flat at the end with sharp edges, not rounded. The first time I used it on my old K-5, I fitted the adapter to the camera and then screwed the lens in, but met with a little resistance when the lens was almost fully screwed in. I had the same resistance when removing it - in fact, it got stuck, and I had to use some force to unscrew it. What I subsequently found was that the diaphragm pin had fouled the two gold-coloured electrical contacts just inside the camera's mount, and it actually carved small channels into those contacts. Not good.
It's possible that the pin on mine was a replacement, or it could be that some or all of them were like this from the factory. If you buy one and the pin looks quite long compared to other M42 auto-aperture lenses, you have a couple of choices... (1) file a small amount off the end of that pin, and round the edges so that it will follow the contours of the electrical contacts as you screw it into place, or (2) remove the locking piece from the M42 adapter, fit the adapter to the lens first, then fit the combined unit to the camera (which avoids you having to screw it into place). The downside with the second option is that the lens and adapter won't be locked into place, so you need to be a little bit careful to ensure you don't unmount the lens in use.
When choosing an M42 adapter, I'd recommend you either get a new-old-stock or used genuine Pentax adapter, or a *good* quality equivalent. The really cheap Chinese knock-offs work, but are machined to quite variable tolerances and can often be difficult to fit and remove from the camera. Either way, you want a flush-fitting adapter, not the "flanged" type (as these won't allow you to focus to infinity).
Last edited by BigMackCam; 05-17-2018 at 03:03 PM.