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02-21-2010, 05:06 PM   #1
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Using M42 (lens) to PK (body) adapters

Well, I'm considering getting an M42 lens (so cheap!) but I'll also need to get an adapter. When I tried looking this up I get a bunch of stuff about digital cameras and autofocus that just doesn't apply to me (still using the K1000. I'm too happy with it for an upgrade to be worthwhile).
There are two areas that I'm still confused about after googling. Infinity focus, and aperture control. Are there different grades of adapters, some which allow infinity focusing and some that don't? And does it affect aperture controls in anyway?

M42 Lens To Pentax PK K Mount Adapter Focus Infinity on (item 270527078897 end time 08-Mar-10 02:47:51 EST) will something like that actually work? And what the hell is that extra metal bit?

02-21-2010, 05:39 PM   #2
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ebay seller says the metal bit is a removal tool. And the one I had, I bought from Pentax. It did work. And worked quite well on my K1000. However, mine didn't look like that one. Mine just locked in like a lens would, twist and turn.
02-21-2010, 06:19 PM   #3
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If the adapter is the type with a "fat flange" - after mounting it on the camera the flange sits on top of the lens mount, instead of completely inside the mount - the you won't be able to achieve infinity focus (the flange keeps the M42 lens slightly too far away from the film plane). Same idea whether film or digital.

As to aperture control, with the adapter there is none! K-mount bodies don't have the same mechanism as Spotmatic (screwmount) bodies have for activating the stop down mechanism in the lens. M42 lenses will have a pin that gets pushed in (IF it has an auto function) while K-mount lenses have a lever that gets pushed sideways.

Just keep in mind the "sunny 16" rule!!
02-21-2010, 06:44 PM   #4
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Hmm, I know the lens I have in mind DOES have the pin (as well as an auto/manual switch), do you know if the aperture will then either be stuck open all the time? Or does the aperture just go where you set it and mess up the TTL metering?

Ohhhh 15 minutes until the ebay auction ends and I'm still undecided. $2 lens, $13 shipping, $8 adapter... I don't know if it's worth it if I'm doing fractions all the time.

edit: did a bit more googling. Decided to get it anyway. I love ebay.

Last edited by redherring; 02-21-2010 at 07:02 PM.
02-21-2010, 09:56 PM   #5
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I recently got the Helios and the same adapter. Took me awhile (after searching on Youtube) to work out that I had to first put on the adapter, then the lens.

It made it quite a hassle to use then got some advice on this post that we can unscrew the little spring clip, leave it on the Helios (I even used a few drops of glue to make it stay) and treat the Helios as a a normal K-Mount lens. Much easier to use now.
02-21-2010, 10:05 PM   #6
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On a K-mount with adaptor:

If the lens is set to auto, the aperture will always be wide open so you can only influence exposure using shutterspeed and ISO. If the lens is set to manual, the aperture will always be in the position that you set it to.

Therefor I use those lenses in manual mode (on the lens).

For focusing, it's advisable to focus while aperture is wide open as it's easier (more light). Next turn the aperture to the desired value, adjust the shutterspeed for proper exposure and shoot.

02-21-2010, 10:14 PM   #7
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Nice! That's what I was hoping to hear! (hoping... not expecting...)


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