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06-07-2012, 07:18 AM   #1
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Using old screw mount asahi lenses wont focus to infinity???

Hey guys i have purchased a few asahi screw mount lenses and found out that they do not focus to infinity on my k-x. any suggestions on how to get it to work do i need to put like a screw mount spacer in to get it to focus properly, will it even be able to focus to infinity? the lenses i bought were a 55 f1.7 and a 35 3.5 there super cool lenses and they take great pictures but you have to be close to the subject your shooting to get it to properly focus. i have a concert to shoot tommorow and i would like to be able to use theme tommorow so any help soon will help alot!!

Thanks,
Carlyn

06-07-2012, 07:41 AM   #2
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i would say it's du to the adapter from M42 to K that might be too long. try to screw a little bit more the lens in the adapter if you can, but don't force it if you can't.

To correct the problem you just have to stop down the lens : it will increase the Depth of Field (DOF).

If you are indoor, the 35/3.5 could be a little slow, but the 55/1.7 will be awesome
06-07-2012, 07:59 AM   #3
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There are some adapters that have a lip that does not allow the lens to set flush to the mount. Another adapter that sits inside the mount might help.
Pentax M42 42mm to PK K Mount Adapter Infinity focus | eBay
06-07-2012, 08:00 AM   #4
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you are using a flanged adapter I assume. it is likely very easy to solve your problem. you need a genuine pentax kmount adapter. or (though I never recommend it, despite what others say) a cheaper knockoff version such as the 'bower' branded ones. these will lock into the kmount without having anything between the mount and the lens, thus retaining the necessary registration distance of he lens. the m42 mount and kmount share the same registration distance. thus you need a 'flangeless' adapter to retain infinity focus.

in short, this is what you need:
Pentax Mount Adapter K (M42 Screwmount to Bayonet) Reviews - Pentax K-mount Teleconverters and Adapters - Pentax Lens Reviews & Lens Database

06-07-2012, 08:16 AM   #5
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With no lenses on and just the adapter mounted take a look at it. The adapter should sit flush or even slightly below the metal mount. If the adapter is proud, (extends above the metal camera mount) you have a lipped adapter which will not permit the lenses to focus to infinity. The reason is that the slight extension of the adapter increases the lens registration distance (the distance from the lens element to the sensor plane). In some cases this can be good, extension tubes do the same thing to allow you to focus closer. That type of adapter is useful with bellows or macro lenses where you are focusing closely or with some very long tele-photos that can focus beyond infinity. But for everyday use it does not work well. The folks above gave you good links and advice on which adapter to get.

If your adapter does sit flush, then you have something else wrong, so let us know.
06-07-2012, 08:32 AM   #6
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Welcome Carlyn!

Can't focus to infinity means the M42-K adapter is too thick, or the adapter is not completely threaded onto lens. +1 suggestions to use only the genuine Pentax adapter...

A very, very, remote possibility is somebody has adjusted the focus helicoids on all the lenses to permit focus when mounted on Nikon camera -- if all the lenses were received together this possibility seems more likely, while the possibility is extreme unlikely if lenses were received separate.
06-07-2012, 08:44 AM   #7
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hey guys thanks for the advice! i did not relize i picked up the wrong adapter i guess thats why it was cheap on ebay ha( it is the one with the lip by the way). well since i need this for a gig tommorow do you think filin down the liped adapter would help any?
06-07-2012, 09:16 AM   #8
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QuoteOriginally posted by carlyn.warnock Quote
hey guys thanks for the advice! i did not relize i picked up the wrong adapter i guess thats why it was cheap on ebay ha( it is the one with the lip by the way). well since i need this for a gig tommorow do you think filin down the liped adapter would help any?
i wouldn't recommend that. you'd have to file it down to non-existence basically. the two mounts have the same registration distance, as i stated before. quite simply, that means you can't have anything between the mount and the lens, if you wish to retain infinity focus.

06-07-2012, 09:42 AM   #9
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While yes you probably want to get the right adapter, how far from infinity does focus stop, and how far will you be from the stage? Are you sure it won't work as is for now?
06-07-2012, 11:03 AM   #10
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I'll be able to be on stage or in front of the stage so pretty close but i have to be closer than 6 foot away from the subject im shooting for it to be in focus. so that means i cant really get good full body shots with the 55. the 35mm you can only be about 3 foot from the subject to get them in focus.
06-07-2012, 11:05 AM   #11
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QuoteOriginally posted by séamuis Quote
i wouldn't recommend that. you'd have to file it down to non-existence basically. the two mounts have the same registration distance, as i stated before. quite simply, that means you can't have anything between the mount and the lens, if you wish to retain infinity focus.
so would the lip of the adapter that locks the adapter be what is cause the issues or are you saying something else is blocking it?
06-07-2012, 02:48 PM   #12
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Carolyn, the adapter must be flush with the metal camera mount. If it extends at all beyond that you will have problems. The lens must seat exactly onto the metal of the camera mount not just onto the adapter. There really is no practical way to modify the adapter you have, your lens will not focus to infinity with it.
06-07-2012, 03:31 PM   #13
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Great tips here, as I was looking at some m42 Takumars for the k-5 and wasn't so sure about infinity focus.

Would anyone mind posting the lipped and non-lipped adapters, so I know what to look for?
06-07-2012, 04:05 PM   #14
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QuoteOriginally posted by snake Quote
Would anyone mind posting the lipped and non-lipped adapters, so I know what to look for?
Get this


Not this
06-07-2012, 04:25 PM   #15
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crewl1, on my computer screen I see only free space what probably should be pictures or links.

Here are examples of the 2 types (self-explaining):

http://www.ebay.de/itm/M42-Schraubgewinde-PK-Pentax-Linse-Kamera-Adapter-/22...item3372babf4f

http://www.ebay.de/itm/Pentax-M42-42mm-to-PK-K-Mount-Adapter-Infinity-focus-...item4ab7649e96
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