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12-11-2009, 07:37 AM   #1
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M42 Supertak 55 f1.8 focusing issues

Hi,

I recently acquired a Pentax SV with the Supertak 55mm f1.8 lens. It is my best looking / best feeling camera. I took it out for a spin and I'm noticing some focusing issues. Looking thru the viewfinder, "infinity" is about 15-20 feet away, but beyond that it is never in proper focus. I took this series of test shots and the only useable pictures are those at f16, maybe f11. Below that I'm not getting proper focus.

1/125 f16



1/250 f11


1/500 f8



1/1000 f5.6



I don't have equipment to test for accuracy, but the shutter speeds seem to be ok and consistent with other cameras. The lens is properly seated/installed.

This morning I took my Spotmatic and swapped the Helios 44 lens and the issue follows the lens. I can't get to focus to infinity in the Spot either. The Helios focuses fine in the SV. This was a viewfinder test. No actual shots were taken on film.

Could this be an adjustment issue on the lens? If so, how can I proceed? Both the lens and the body look pristine with no obvious signs of repairs.
I have some experience disassembling lenses if needed.
Can somebody point me in the right direction?

Thanks,

12-11-2009, 09:43 AM   #2
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There is an adjustment for this, and it shouldn't be that hard for you. Remove the trim ring around the front element (the ring that has the lens name engraved on it). You should see something like this, except your screws will be common slotted screws:



Then remove the three screws holding the ring with filter threads on, either the only screws you see or ones like are marked with red arrows in the photo above. Remove the filter ring and you'll see something like this:



The screws marked with red arrows are next. First, turn the focus ring so that the focus indicator points to the infinity mark. Then loosen the three screws enough so that the focus ring can move without focusing the lens. Move the ring back to the 15 ft. mark and tighten one screw. Now you can turn the focus ring a little farther. Then mount the lens on a camera and see if the lens focuses to infinity. If not, repeat the steps until it does. Then tighten all the screws, reassemble the filter ring, etc. and you're done.

I prefer to use a film camera viewfinder with a split prism to check focus. You can do it with a DSLR too, maybe looking at wide-open shots at 100% to be sure.
12-11-2009, 12:41 PM   #3
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Dave's instructions are certainly correct for a miss-adjusted focusing ring, but before you go to that trouble check to see that the REAR element is properly screwed in.

I've also come across one 50 that someone had apparently swapped a rear element for a "better one" not recognizing that while they may look the same, and fit, they're not identical.

H2
12-11-2009, 04:46 PM   #4
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Original Poster
Thank you both VERY much!
That's the guidance I needed to get started.
I'll let you know the results.

Thanks,

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f11, f16, focus, helios, issue, k-mount, lens, m42 supertak, pentax lens, shots, slr lens, supertak 55 f1.8, test
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