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06-04-2012, 06:51 PM   #1
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Pentax K-r and manual lens

Dear fellow Pentaxian,
Just received SMC Pentax M 75-150mm F/4, work well in the first day, however the next day I found
some trouble in which after the shot it seems that mirror failed to return to its possition, only after
removing the lens from the body it work again only for one shot then again it failed to operate
because mirror can not go down. Have anyone of you guys have simillar experience with manual lense ?
I used manual prime 50mm without any problem, can you suggest what might be the cause and
the remedy ? Thanks alot for any suggestion.

06-04-2012, 07:12 PM   #2
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I don't have this lens but check to see if the rear element goes any deeper into the camera body than your 50mm prime. If so, it may be just catching the mirror.
06-04-2012, 07:18 PM   #3
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It shouldn't be a rear element issue with an M series lens.

OP, are you saying that you can reproduce the problem reliably, that it goes away with your 50mm (and how about your kit lens, or any others), but comes back whenever you mount the 75-150mm?

That would be quite odd. I suspect that the problem's timing is coincidental with acquiring the new lens. It sounds like a failing mirror mechanism, just from wear or defect. Is your K-r still under warranty?
06-04-2012, 07:31 PM   #4
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Pntax K-r and manual lens

Thanks for responding,
It is true that when I examine the SMC Pentax M 75-150mm f/4, the black protruding
plastic of the back lens element is bit longer than the other lens. And yes I tried afterward
with all other lenses without any problem, only with this one.
Can I just file the plastic part to make it shorter ? will that cause even more problem ?
Unluckily warranty time is just over.
Thanks for your kind advises

06-04-2012, 08:42 PM   #5
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Could you post a picture of the lens mount?

I think if the mirror were really catching on it, there would have been damage done before now, but I could be wrong.
06-04-2012, 08:49 PM   #6
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I have that lens and the rear element does not protrude at all. The aperture lever protection flange is the only thing extending out from the rear and it extends 12mm, same as other Pentax lenses. Lens work just fine on both k-x and k-5.

Not sure what the problem is but I would not start filing anything yet. Post a picture of the rear of the lens so we can see if anything is wrong.
06-06-2012, 06:41 AM   #7
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Have solved the problem, actually its all due to the aperture lever and the protection flange were too close together almost touching one with the other and nothing to do with the mirror mechanism. A little work with Swiss Army knife did the job and all is ok now. Thanks for responding to my post.

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