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05-31-2010, 05:43 AM   #1
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Asahi Super-Takumar 1:1.8/55mm Lens won't focus to infinity

I recently bought my wife a K20D. I also got her the screw-mount lens adapter.

I turned off the aperture ring requirement in-camera and the lens takes INCREDIBLE shots of close and medium-distance objects but it won't focus to infinity for some reason.

After mounting the lens and booting the camera it asks for the focal length and I've tried it on every setting and it doesn't seem to make any difference.

Any ideas? Thanks in advance for any help.

05-31-2010, 06:05 AM   #2
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You need an adapter that fits inside the camera, like the genuine Pentax adapter.

Hin's Tech Corner: Genuine Pentax M42 to K Adapter

Adapters with a wide flange change the registration distance by a mm or so. Thus the loss of infinity focus.

https://www.pentaxforums.com/forums/camera-studio-accessories/96884-adapters-...addiction.html

Last edited by boriscleto; 05-31-2010 at 06:15 AM.
05-31-2010, 06:35 AM   #3
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The first thought is indeed that you have an adaptor with a flange (like boriscleto said).

QuoteOriginally posted by bingostew Quote
After mounting the lens and booting the camera it asks for the focal length and I've tried it on every setting and it doesn't seem to make any difference.
That is only for shake reduction purposes and has no relation with you problem.
05-31-2010, 06:48 AM   #4
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Bingo, you have entered into the wonderful M42 adapter controversy. Here's the deal:

1) Some will argue to only get the genuine Pentax adapter, like me. Much more expensive, but a better machined piece of "equipment," and easy to remove. Have you tried to remove YOURS yet? The 3rd party ones can be a nightmare, and the trick is to remove the screw and spring thingie so that it's only held on by friction. People have shed tears trying to remove the discount ones with the locking clip attached.

2) Believe it or not, Pentax didn't make this adapter available for a period of time, so I suggest you get one now while it is.

3) I bought a Bower from B&H that wouldn't even FIT in the mount. Another Bower did. And gee, aren't experiences like THESE loads of fun!?

4) With the Pentax adapter, the Pentax M42 lenses fit fine, but she may find that with the 3rd party lenses (Vivitar, etc.), the aperture ring doesn't line up correctly at 12 o'clock when the lens is fully tightened. It may be toward the SIDE of the lens, but it is still totally functional like this.

5) To reiterate what was said above, it asks you for focal length (FL) only to tell shake reduction how to operate. For a zoom lens, set it for the FL you think you're going to be using, or turn SR off.

6) I guess you've already discovered the F-- display. With a manual lens, the camera doesn't know what you're doing as to aperture. This is also why aperture info is not included in the EXIF data. (It hurts me big time, but what can you do?)

7) Is she shooting in Aperture Priority (Av) or Manual? Tell her that with M42 Taks, Av has been known to consistently underexpose up to 2 stops!!! So tell her this is to be expected. Some people just set the compensation. I prefer to shoot in M mode and use the green button. (On the K-x, I can use the ev button, but that's another story.) M mode meters wonderfully for me for all of my Taks, EXCEPT THE SMALLEST APERTURE WHICH UNDEREXPOSES. In addition, she may find that with certain lenses, when you get down to F22, F16...depending on the lens...you won't get focus confirmation. So, you focus wide open, and then stop down to the aperture you want.

Just wanted to let you know some of these quirks, but they're all tolerable, and the joy of using the old classic glass more than make up for them.


Last edited by Ira; 06-01-2010 at 08:36 AM.
05-31-2010, 06:10 PM   #5
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Woah. Thanks guys; you're fast. My Dodge forum people usually take a few days to get around to helping me out... and my car issues way more urgent than my wife's camera woes. (Don't tell her I said that.)

Yeah I bought an el-cheapo adapter from eBay. I think it was like $7 bucks shipped. I'd never have considered it could be the flange on the adapter. It's pretty astounding that something so minuscule could have such a dramatic impact.

Thanks again for the help! I'll be back with more noob questions you-can-be-sure.
05-31-2010, 11:42 PM   #6
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QuoteOriginally posted by Ira Quote
...
...

4) With the Pentax adapter, the Pentax M42 lenses fit fine, but she may find that with the 3rd party lenses (Vivitar, etc.), the aperture ring doesn't line up correctly at 12 o'clock when the lens in fully tightened. It may be toward the SIDE of the lens, but it is still totally functional like this.

...
...

the joy of using the old classic glass more than make up for them.
Your experience is definitely different from mine; SMC and Super Taks don't align at 12 o'clock either on any of my two genuine adaptors. Not that it matters much

And indeed, it's the joy of reviving that classic glass on a digital body. It brought my fun in photography back after I switched to a dSLR.
06-01-2010, 08:35 AM   #7
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QuoteOriginally posted by sterretje Quote
Your experience is definitely different from mine; SMC and Super Taks don't align at 12 o'clock either on any of my two genuine adaptors. Not that it matters much
That's weird--every one of mine does. Maybe it has to do with the lot they come from.
06-01-2010, 12:34 PM   #8
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Indexing

QuoteQuote:
... don't align at 12 o'clock ...
I consider that a good thing and prefer that they don't align at 12 o'clock so the aperture index isn't hidden beneath the flash hood.

I even shave a fraction of a millimeter off the seating depth or shim the adapter to cause the lens to index at the 10- or 2-o'clock position on those lenses with an adapter semi-permanently attached. (The lens registers off the mount so no change in focus is involved.)

H2

06-03-2010, 03:32 AM   #9
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Thanks for all the help folks.

So just to confirm, this is what I need?

PentaxWebstore Mount Adapter K(35m m Screwmount to Bayonet)

It looks to me like there's still a flange; the lens still won't be sitting flush with the body.
06-03-2010, 05:10 AM   #10
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QuoteOriginally posted by bingostew Quote
Thanks for all the help folks.

So just to confirm, this is what I need?

PentaxWebstore Mount Adapter K(35m m Screwmount to Bayonet)

It looks to me like there's still a flange; the lens still won't be sitting flush with the body.
That's the one. No worries. And if they offer expedited shipping (don't remember), go for it.

I got mine fairly quickly, but others waited un-Godly periods of time. However, I think that was because they just didn't have them, and they were being manufactured at that time.
06-03-2010, 06:53 AM   #11
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Ordered.

They wanted an extra $23 bucks for expedited shipping... I'm certainly doing better than I used to be but I'm not stupid

She can wait.

thanks y'all!
06-03-2010, 08:34 AM   #12
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QuoteOriginally posted by bingostew Quote
PentaxWebstore Mount Adapter K(35m m Screwmount to Bayonet)

It looks to me like there's still a flange; the lens still won't be sitting flush with the body.
That flange will 'fall' inside the mount and your lens will be flush with the mount.
06-03-2010, 08:43 AM   #13
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QuoteOriginally posted by sterretje Quote
That flange will 'fall' inside the mount and your lens will be flush with the mount.
Ah. Should've figured that. Cool.
06-03-2010, 09:03 AM   #14
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QuoteOriginally posted by Ira Quote
That's weird--every one of mine does. Maybe it has to do with the lot they come from.
Depends on the adapter. I have two genuine Pentax. One lines up and the other doesn't. Go figure...
06-03-2010, 09:20 PM   #15
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Adjusting lens index

QuoteQuote:
Depends on the adapter. One lines up and the other doesn't.
You can adjust the position of the lens when using an M42 adapter. Since the M42 mount uses a 1mm thread pitch, 1/36 mm = 10 degrees of rotation. You can shim or shave the lens/adapter mating face to suit your preference.

If the lens indexes beyond the desired position, build up the mating surface with thin coats of fingernail polish, paper, aluminum foil, etc.

If it doesn't rotate far enough to suit you, remove a little metal from the adapter mating surface by "polishing" it on fine sand paper.

As mentioned above, I prefer to have the lens index at the 2-o'clock position to better view the aperture index mark in manual mode. Unfortunately, that requires the more time consuming 'shave' method so I cheat and do it on a lathe .

H2
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