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10-18-2011, 11:39 AM   #1
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Old lens inspection

I am about to buy an old lens and I would like to know what I should verify? I know I should look for dust inside the lens and scratch on the front and back lens. Other than that, is there anything important (physical inspection) I should verify to make sure I am not buying a lemon?

10-18-2011, 12:08 PM   #2
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I find that dust is the last thing on my list of things to look for as I believe it has minimal effects in the iq. I'm more worried about fungus growth. and the 2nd thing I check for is the aperture blades and making sure they are clean and clear of any oil. After that it is the mechanics of the lens, focus ring is smooth and aperture lever and ring is functioning properly. Lastly I worry about the dust.

Buying used for Pawnshop Lenses. Good read for you.
https://www.pentaxforums.com/forums/pentax-lens-articles/59245-pawnshop-lense...ers-guide.html
10-18-2011, 12:37 PM   #3
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QuoteOriginally posted by SylBer Quote
I am about to buy an old lens and I would like to know what I should verify? I know I should look for dust inside the lens and scratch on the front and back lens. Other than that, is there anything important (physical inspection) I should verify to make sure I am not buying a lemon?
Do you buy an AF or MF lens? If AF your really need to test to AF functionality as well so you really need to mount it on your camera. The rest I agree with previous poster.
10-18-2011, 04:50 PM   #4
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https://www.pentaxforums.com/forums/pentax-lens-articles/59245-pawnshop-lense...ers-guide.html

10-18-2011, 08:22 PM   #5
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Excellent article. I did not find it when I first searched the forum.
10-20-2011, 11:01 AM   #6
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For your information, I followed the instruction in the article and finally bought a Pentax SMC K 85mm f/1.8 that is in excellent condition!
10-20-2011, 05:57 PM   #7
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I would take two tools other than your camera. Take a bright led based flashlight and use it to look through the lens (same direction you are looking) as well as shine it through the lens at you.

I would also use a laser pointer to look through the lens (not into your eyes)

Other than that, make sure it focuses ok, that the aperture stops down with the green button metering, etc...
10-21-2011, 06:10 PM   #8
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Thanks for the advices

Looking through a lens with a light is pretty scary. Most of my lens look perfect in normal light, but I can find tiny dust in all of them.

10-21-2011, 06:14 PM   #9
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QuoteOriginally posted by SylBer Quote
Looking through a lens with a light is pretty scary. Most of my lens look perfect in normal light, but I can find tiny dust in all of them.
I think I mentioned that in the BUYER'S GUIDE. Some are bright and pristine. Some are cobwebby caves, or worse. Almost all have at least some dust. That's pretty normal. If you see things crawling around in there, carefully put the lens down and run away, fast.
10-21-2011, 07:40 PM   #10
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QuoteOriginally posted by SylBer Quote
Looking through a lens with a light is pretty scary. Most of my lens look perfect in normal light, but I can find tiny dust in all of them.
It's a good point to not sweat the small stuff. What you're looking for is broken anything (especially along the edges), any really substantial dust, or fungus.
10-21-2011, 08:10 PM   #11
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QuoteOriginally posted by Clinton Quote
It's a good point to not sweat the small stuff. What you're looking for is broken anything (especially along the edges), any really substantial dust, or fungus.
And crawling critters. It's like food: Don't eat anything that's crawling off your plate. Don't buy a lens with interior motion. No good can come of that.
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