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02-16-2017, 09:33 AM   #1
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Pentax-f smc 1.4 blurry

After sitting idle for a couple of years, my Pentax-f 1.4 has gone blurry in either auto or manual focus. I get the focus confirmation, but nothing is in focus. Tried on two different bodies, same result. No filters present, and glass is clean. Any ideas?

02-16-2017, 10:07 AM   #2
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Wow, Id take DC up on that offer, just to see the legend in the flesh

Check the back lens element for smudges, and make sure the focusing ring turns correctly, without odd resistances or bumps.
02-16-2017, 11:06 AM   #3
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QuoteOriginally posted by jamesmck Quote
After sitting idle for a couple of years, my Pentax-f 1.4 has gone blurry in either auto or manual focus. I get the focus confirmation, but nothing is in focus. Tried on two different bodies, same result. No filters present, and glass is clean. Any ideas?
Does the focusing mechanism seem ok or is it jamming up?

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02-16-2017, 03:06 PM   #4
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Thanks for the comments, and thank you DCshooter for the kind offer. I do live in DC, but am not there right now. All the glass and blades are clean, and the focusing ring works smoothly. Note that the blurriness occurs with both auto and manual focus, and that I do get the focus confirmation blinky.

I am attaching a very artful shot taken out of an open window this afternoon. Lens was attached to a K100D (on which it behaved normally a couple of years ago), but the same problem occurs with a K20D. My Pentax gear is not quite up date to date, as you can see. Thanks in advance for any thoughts.

---------- Post added 02-16-2017 at 05:15 PM ----------

I just noticed that the EXIF for this shot says f/1.4. But, the lens aperture ring was set at f/8. Might this give some hint?

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PENTAX K100D  Photo 
02-16-2017, 04:02 PM   #5
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If you put the ring to a small aperture value (e.g. f/16) and manually move the lever on the back of the lens, do the blades move? Are they slow to return?

Yes, the blades move, and they return quickly.

And if you set the ring to A, can you successfully control the lens from the body? If you shoot in A mode and look in the front of the lens, can you see the iris closing when you take a shot?

Yes, with the lens on A the aperture can be changed from the body, and yes, the iris does close when shooting in A mode.

FWIW, I also took some aperture priority shots with the lens on the K20D today. I just checked the EXIF on one, and it also reports f/1.4 (and I know the lens ring was not set there).
[Later, realizing that lens ring is not read, still wondering why the camera chooses 1.4 regardless of lighting conditions. Other lenses work fine on these cameras.]

Last edited by jamesmck; 02-16-2017 at 04:50 PM. Reason: something added
02-16-2017, 05:18 PM   #6
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Cool effect there. Reminds me of this old Miranda 50mm f1.9 that I have, which cost around $20. It has a similar "glow". I don't know what causes it, though.
Maybe just buy a used DA 50mm f1.8. It will probably be cheaper than official repairs (+shipping), and you get a modern lens with full automation and modern coatings, rounded aperture blades.. plus you get to keep that lens for its crazy, dreamy effect.
02-16-2017, 05:33 PM   #7
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QuoteQuote:
[Later, realizing that lens ring is not read, still wondering why the camera chooses 1.4 regardless of lighting conditions. Other lenses work fine on these cameras.]
With the camera not being able to read the position of the lens ring, it defaults to assuming wide open.

Best solution is to always leave the lens set on A and set the aperture from the body.
02-16-2017, 06:36 PM   #8
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QuoteOriginally posted by blacklite Quote
With the camera not being able to read the position of the lens ring, it defaults to assuming wide open.
Best solution is to always leave the lens set on A and set the aperture from the body.
Thanks for clearing this up. I must admit that I haven't used these bodies for some time, and totally forgot the need to use only the camera to set aperture. Of course, this has nothing to do with my focusing problems with this lens.

02-16-2017, 11:11 PM   #9
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In modes like Av the camera will always use 1.4 if the lens aperture ring is not in the "A" position. You can use manual exposure mode and stop-down metering with the ring set to an F-stop, but no real reason to do so.

Your image is soft throughout, but the brickwork and the tree on the right are the sharpest areas, so I think your problem is simply one of lack of depth of field from using the 1.4 aperture.
02-16-2017, 11:22 PM   #10
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QuoteOriginally posted by jamesmck Quote
Thanks for clearing this up. I must admit that I haven't used these bodies for some time, and totally forgot the need to use only the camera to set aperture. Of course, this has nothing to do with my focusing problems with this lens.
Though if you were using it on 1.4, it might just be a much smaller depth of field you are expecting. In the photo you posted, the windows on the buildings look to be in focus.
02-17-2017, 03:44 AM   #11
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So did you push the little button on the aperture lever and slide the aperture ring into A position? Can you now choose any aperture you want in Av mode?
Because yes, the F series has AF and it has auto-aperture, but auto-aperture is only enabled when aperture ring is in a mode.
02-17-2017, 07:28 AM   #12
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QuoteOriginally posted by pschlute Quote
Your image is soft throughout, but the brickwork and the tree on the right are the sharpest areas, so I think your problem is simply one of lack of depth of field from using the 1.4 aperture.
Well, you (as well as some other respondents) seem to be correct about the cause of my problem. With the lens locked in A mode and a sensible aperture chosen from the camera body, images are properly sharp. My apologies to everyone for this oversight. I will surely never forget this again when using this lens. Thank you all.
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