M42 adapter

I've got two, the Pentax made one and a cheap copy. The Pentax just works better, though I have never had the cheap one stick.

There's two types, the first one allows for infinity focus and sits inside the K mount of the camera, and is released by pulling back a little spring.

The second (cheap) adapter is about 1mm thick and covers the k mount contacts, this version restricts focusing to infinity.

The first option is the better choice, but costs more, a genuine Pentax Adapter can be £30. Before getting my hands on a genuine one, I did have a non-branded one, which fitted fine... just one major bugbear, is that when screwed on the M42 lenses didn't line up with the top, so aperture markings etc were down the side, which I found annoying, With the genuine Pentax one, they lined up perfectly.

I've found two links which may help:
link

link

Post #7 of the second suggests it attaches to the microscope eyepiece.

John.

If you're not mounting a normal lens, then I wouldn't worry about it lining up, since it doesn't matter so much.

However, I'm not sure what the impact would be of using the cheaper option adapter that's 1mm thick and covers the contacts, whether you'd still be able to achieve focus. May be someone else can answer this, since I've no experience of using an adapted microscope.

The ones that are 1mm thick are only a few of quid off eBay, so wouldn't be too much of a gamble.

Get the genuine version. They work well and don't cause problems, especially not getting stuck on your camera rendering it permanently M42-only.

there is a rare kood adapter that fits inside the k mount for infinity focus and has an internal flange that actuates the aperture pin on the lens.

I've just read the comments about, cheap adaptors with protruding flange. Mine is a cheap version but still sits inside the body. Originally it belonged to my father, so it's at least 30 years old, and it looks like he has removed something from between the top and bottom flanges. Could that be the offending part that sticks it to the camera. Unfortunately I can not find any sign of a maker on the box or mount.

As much as I read comments about cheap adapters providing infinity focus, I'd be more concerned about getting the adapter stuck on the camera. Not too bad if it's an old 'cheap' film body, not so great if it's an expensive DSLR.

The genuine Pentax one is the only one I'd use, irrespective of the cost difference, admittedly I have one for sale but I'm rethinking that as they're always useful to have.

I've been happily using 3rd party ones for a while - just ensure that you remove the small metal spring/screw to prevent the mechanism locking up.

You can then put the adapter on the lens before mounting, then use it like a normal bayonet (of course with a little bit more risk since it can dismount more easily).

I've also used the genuine one but that's a bit more annoying to use - only a minute extra but I'm impatient.