Foucs problems with a Pentax-m 40mm f/2.8!!!

I´ve and old 40mm pancake lens and I can´t focus to infinity! How can I do to fix it? can I do it by myself or should I get a professional to do it?

///Anders S

Is the focus screen located properly, some Pentax's have interchangeable screens and these can cause a focus problem.

Ian

I think it´s sitting right. I´ve done a cleaning of it by myself. Perhaps I didn´t put it back as it should be. I´ve to check this.

///Anders S

If you have another Pentax camera, check the lens on that to see if it's the camera or lens.

BetterSense said:

If you have another Pentax camera, check the lens on that to see if it's the camera or lens.

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Thank you! That was a great idea!

///Anders S

Did you disassemble the lens?

elekm said:

Did you disassemble the lens?

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No, I´ve not done that! I know there are three screws to unscrew to adjust the focus! Isn´t it so?

///Anders S

Yes - you first remove the name ring (unscrew it using a rubber block/rubber stopper etc) you will see the 3 screws to loosen so you can move the focus ring a little to adjust infinity focus

But how did you go with the focussing screen - is it sitting correctly? I would check the lens on another camera to see if it is focussing correctly to infinity first. If you don't have another camera I would set the camera to B and check the focus on the film plane with some ground glass (if you don't have ground glass use a piece of frosted sticky tape - run the tape from the top to the bottom of the camera making sure it is stuck to the top and bottom film guides only - you will be surprised how clear the image is to focus on - I use this technique for focussing folding cameras when I've re-lubricated the focussing ring