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03-29-2012, 09:19 AM   #1
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S-M-C Takumar 1:3.5/28 DOF problems

Recently I purchased a S-M-C Takumar 1:3.5/28. (mint)
For some reason when I use the DOF scale on the lens,
I get out-of-focus at infinity. I also tried f11 and set
The infinity mark at f5.6 mark with the same result.
( less out-of-focus but still not right)
But when I set the lens to infinity and use f8 it works fine.
I have tried different adapters, known to be good.
Using this lens on a 7D. Confirmed problem in live view.
Has anybody have the same problems or does the lens have a defect?
The direct focus works fine, even at close-up.
Thanks

03-29-2012, 09:57 AM   #2
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I'll let wiser people than me give better reasons, but in my experience the DOF scales on 35mm film lenses are overly optimistic when working with digital APS-C. In fact I did what you did, I took a SMC-A 28/2.8 on a trip with a K100D, and optimistically I used the DOF scale like I'm used to with film. Result- lots of out of focus pics.
03-29-2012, 07:41 PM   #3
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Figure that the DOF scale on a FF lens is about 1 f-stop off for APS-C cameras. When I use zone-focus, I adjust by just one stop. So if the lens is a f/11, I read the DOF scale at f/8. For hyperfocus, where the zone extends to infinity, I fudge it a bit to make sure infinity will be in focus. So I may set the lens to f/11, then set the infinity mark to a bit inside the f/8 mark, like around f/7 or thereabouts.
04-01-2012, 04:27 PM   #4
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QuoteOriginally posted by takpix Quote
Does the yellowing of the lens effect focus and DOF?
no it doesn't, it only affects the colour balance - however a custom WB pre-set should negate it's impact.

QuoteOriginally posted by takpix Quote
maybe to try to adjust (move) the infinity mark.
Only if you really know what you are doing. Sometimes the M42 adapter you are using can prevent infinity focus, I would check on this before unscrewing anything.

04-01-2012, 05:06 PM   #5
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QuoteOriginally posted by takpix Quote
t was easy to unscrew the ring and make adjustments to it.
just a question which ring are you unscrewing?
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