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04-21-2010, 02:15 AM   #1
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Focusing problems with a Pentax-M 40mm f/2.8!!!

I own a 40mm 2.8 lens and I have problems with it. Its a manual lens and when Im using it with both the old MX body and my new K200D body the lens would not focus on infinity? How can I do to make it do that? Can I fix it by my self or should I send it to someone who is a proffessional?

///Anders S

04-21-2010, 04:46 AM   #2
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You can fix it yourself. But you need to be at least a little bit handy and technical. It will probably come apart something like this.

I have corrected the focus on my 50mm f/1.4 and it was quite simple once I got that hang of it. If I remember correctly there were three screws holding the front part of the lens in place and once loosened you can rotate the front element to adjust infinity focus.

I have no idea if this is also true for the M40/2.8 but you could always have a look, the old lenses (especially primes) are not that complicated to work with anyhow so you could probably work it out.
04-21-2010, 06:07 AM   #3
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In another forum for analog photography a guy said it can be the focusing screen that is not in place.
04-21-2010, 06:10 AM   #4
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I doubt both cameras have out of place screens. I would suspect the lens for a problem like yours.

04-21-2010, 08:30 PM   #5
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You have to unscrew the ring that says SMC PENTAX-M 1:2.8 40mm, using some sort of friction tool, rubber crutch tip, etc. Then you'll see three screws in cutouts and three more screws holding on the filter ring. Remove the filter ring screws and the filter ring. There's three more screws on the outer edge which hold the focus ring to the focusing helix. It looks something like this M50/1.7, and the screws you want are marked with red arrows:



Put the lens on a camera. Turn the focus ring to the infinity stop. Loosen those three screws. Now you can turn the focus ring back a bit, maybe the 10 meter mark, without changing the focus of the lens. Tighten one screw and see if you can focus to infinity now. After some trial and error, you should be able to focus to infinity again. Tighten all the screws, reinstall the filter ring, put the trim ring back on and you're done.

Since you have a film camera with a split prism fiocus screen, finding infinity can be a little easier with that camera because the viewfinder's bigger and brighter.
04-22-2010, 04:31 AM   #6
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QuoteOriginally posted by Just1MoreDave Quote
Since you have a film camera with a split prism fiocus screen, finding infinity can be a little easier with that camera because the viewfinder's bigger and brighter.
It were there I saw it. And then I remembered that Ive cleaned the focusing screen on the old camera and maybe it was the screen that was out of place. I pointed the camera on a radiotower not far from me, and then tested it on the K200D-body and tryed to focus to infinity and then zoomed in to look att the picture. The picture where blurry on the leg of the radiotower. I have not changed the FS on the K200D-body.

Thank you! I should try this right away.

///Anders S
04-25-2010, 10:02 PM   #7
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I have found the problem. It was the focusing screen. I tried to push it up little bit and then checked it again. So now I can focus to infinity.

Thank you guys!!!
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