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01-28-2011, 04:38 PM   #1
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Used Lens: What Quick Checks before you buy?

I shop at a jumble sale, and wished to purchase a lenses. However, I never purchased a used Lens from someone not online or in a shop. So:
  • What quick checks should I do before I buy the lens? (Beyond the obvious: checking the F ring, the focus is smooth)
  • How can you quickly determine if the glass is not damaged
  • Is there a quick way to spot a Pentax Mount vs. one for another camera.


01-28-2011, 05:18 PM   #2
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Make sure the rings turn smoothly. Make sure the lens stops down quickly and opens up quickly again when the lever on the bottom is flicked. Shine a penlight through from one end looking in the other, that will show you internal haze or fungus as well as the degree of internal dust.

As for the mount, with just a little time you should be able to recognize one. One trick would be to bring along a K1000 or similar manual SLR. You could be sure it mounts. And then with the back open you could fire it at top shutter speed to be sure it stops down all the way to its minimum (largest number) f stop.

Good luck!
01-28-2011, 06:32 PM   #3
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Good info from Nick, don't forget a bright flashlight. Check for oil on the aperture blades too. Make sure that aperture lever looks good to. Also check the filter threads for dents and shake it a little for loose parts inside. If you don't have a camera to mount it, do a good visual to make sure it hasn't been abused. Hope you find some gems!
01-28-2011, 07:11 PM   #4
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If I may be a bit immodest... I wrote the canonical guide [ ] that some members here think is worthwhile. Good luck!

01-28-2011, 07:15 PM   #5
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Indeed RR, I should have mentioned that.
01-28-2011, 08:05 PM   #6
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Why not print up a focus test chart and keep it handy in the car/camera bag,
a quick test on a counter top could reveal focus, sharpness issues before buying a bad lens.

PENTAX DSLRs: PART-1. Free Autofocus Adjustment charts for front and back focusing problems. Good for Pentax, Canon and Nikon.
01-28-2011, 08:10 PM   #7
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+1 flicking the aperture lever at the rear whilst watching the blades, with lens set to f16/f22. Check the screws at the rear to see if someone ham-fisted has been in it: a decent repair guy will not chew screws up.

Take your camera along and try shooting a few pics off. Get a M42-K mount converter in advance. Main duty for my *ist DS is to test the lenses I buy.

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