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09-23-2012, 07:39 AM   #1
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SMC 50mm 1.7 m not focusing to infinity?

I have just got a SMC 50mm 1.7 m which I want to use on my Pentax K7 It seems really good except it will not focus to infinity. Why would this be happening as I thought it was just some lenses used with an adapter that would not focus to infinity.
I look forward to your thoughts

09-23-2012, 07:48 AM   #2
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QuoteOriginally posted by juglas Quote
I have just got a SMC 50mm 1.7 m which I want to use on my Pentax K7 It seems really good except it will not focus to infinity. Why would this be happening as I thought it was just some lenses used with an adapter that would not focus to infinity.
I look forward to your thoughts
How can you tell it doesn't do infinity, did you test with a tripod and live view pictures of something really distant, like the moon?
09-23-2012, 08:13 AM   #3
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When I look through the viewfinder it looks blurred at infinity, I tried taking pics at f22 and they look less blurry than f 1.7 obviously, it almost seems like the camera is backfocusing?.
09-23-2012, 08:26 AM   #4
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Very simple to adjust, look up Pentax 50 mm repair adjust on the net.

09-23-2012, 09:07 AM   #5
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Judging sharpness through the viewfinder is not the best idea honestly. Judging sharpness looking at pictures taken at f/22 isn't, either. Can you please describe the object you were focused at infinity, and distance, approximately? There is a chance that the lens is working properly and it's just new to you, so don't disassemble it just yet.
09-23-2012, 12:43 PM   #6
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It is quite obvious that it does not focus on distant objects. close up it is great.
09-23-2012, 07:19 PM   #7
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QuoteOriginally posted by juglas Quote
It is quite obvious that it does not focus on distant objects. close up it is great.
It's quite likely it was repaired or cleaned and not properly adjusted on reassembly. I have a FA50/1.7 that was severely like that and an M28/3.5 that was a bit like that. I got a knowledgeable friend to tweak them, successfully. I believe once you get the front off it's quite easy to adjust, requiring a small screwdriver and a bit of trial and error. You have to loosen the right screws though - there are two visible sets of three (if I remember right) and you have to loosen the right ones. You have to locate the external focusing ring correctly in relation to the innards. With live view it's much easier to get infinity adjusted right than it used to be without it.

Tim
09-23-2012, 07:24 PM   #8
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It is not to hard to adjust, and also quite easy to tell if it is not reaching infinity (or sometimes, going past infinity) if you use liveview as then the viewfinder doesn't come into play.

09-25-2012, 12:33 AM   #9
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Thanks for your feedback everbody.
09-27-2012, 07:11 PM   #10
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How did you try to focus the lens? Are you saying you carefully focused and couldnt get a sharp image because the ring wouldn't turn far enough, or did you just slam the rong to the end thinking that would be infnity? it's actually often a bit *past* inifnity; you have to actually focus.
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