Confused over M42 Adapters

rick_oleson · Posted: Sat Oct 04, 2008 10:29 pm Post subject:

If it has a stop-down button, you can use it without a flanged adapter and push the stop-down button just before you release the shutter. This is more convenient than a flanged adapter anyway, because it lets you focus with the lens wide open and then stop it down qucikly just as you are about to shoot.

None of this has anything to do with focusing to infinity, though .... you've lost me there.
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Throndor · Joined: 15 Sep 2008 Posts: 156 Location: Ankara / TURKEY

rick_oleson · Posted: Sun Oct 05, 2008 1:57 am Post subject:

We're talking about two different flanges on two different adapters that do two different things:

If you want to adapt an M42 to a K mount, the proper adapter fits flush inside the mount, with no flange sticking out in front. If you get an M42/K adapter with a flange around the outside on the front, you will not be able to focus to infinity on a Pentax K body.

But we're talking about adapting an M42 lens to a Canon. These adapters always have a flange on the outside, because the register distance of the M42 is longer than that of the Canon so you need an extra mm or so out front. But that is not the flange that we've been talking about up to now: the "flanged adapters" here have a flange on the INSIDE, in the BACK end of the adapter. The purpose of this flange is to depress the auto diaphragm pin on the lens as you screw it into the adapter. This flange has no effect on focus, unless you have an incompatible lens that hits the flange before it's fully seated into the mount.

Sorry if this is wordy, I'm trying to unconfuse you a little bit.
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Throndor · Joined: 15 Sep 2008 Posts: 156 Location: Ankara / TURKEY

Ah, thanx.. Clearer now..
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rick_oleson · Posted: Sun Oct 05, 2008 1:59 pm Post subject:

No problem!

Back to your situation with the M42-K adapter: As you suggested, you want a flangeless adapter that will fit entirely within the K bayonet, in order to allow infinity focus. The "flanged" M42-K adapters are easier to install and remove, but they will not allow infinity focus.

In either case, these adapters (the ones that I've seen, anyway) do not have a flange inside in the rear to depress the auto aperture pin in. So with any K mount adapter, you will want an M42 lens that will let you close the blades without having the auto pin pressed in from the back. These would include any lens that has an Auto/Manual switch; any lens that has a stopdown button; early auto lenses that required you to manually reopen the blades with a cocking lever on the side of the lens; and any manual or preset lenses. The only ones that will be a problem are auto-only lenses with no manual switch.
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montecarlo · Joined: 04 Apr 2007 Posts: 1568 Location: Romania

gembobs · Joined: 02 Oct 2008 Posts: 3

I have bought a brass adapter with AF confirm chip with a flange - I figured that if the Soligor needs the flange it will work, if it doesn't then it may still work! If not, then it is no great loss!

Many thanks for all the tips and advice given, it is greatly appreciated!