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Archive 2013 · How to check a lens in the real world?
  
 
trueimage
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p.1 #1 · p.1 #1 · How to check a lens in the real world?


When buying used lenses, in the absence of charts, rulers, tripods, etc what are the things that you do to check a lens in a real world scenario?

Here are some of mine:


  1. do the transaction in daylight, outdoors or near windows
  2. check the exterior of the lens for cosmetic damage or missing switches/screws or things that look replaced
  3. check the filter ring for dents or dent repair
  4. check the zoom motion is smooth and doesn't droop
  5. check the MF ring and make sure it moves the distance scale
  6. check all switches
  7. check the front and rear elements
  8. look through the lens from both ends, changing angles to see any marks, fungus, etc
  9. put the lens on the camera and test the AF and MF at wide, middle and tele zoom focal lengths
  10. stop down to minimum aperture, hit dof preview and take the lens off the body with the blades out - repeat the examination of the lens and blades
  11. take some test shots for AF accuracy, vignetting, distortion


any suggestions to add to this list would be great - as you can see this is really light on the actual optical quality of the lens...



Feb 27, 2013 at 06:01 PM
jcolwell
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p.1 #2 · p.1 #2 · How to check a lens in the real world?


Speaking of checking things, here's my check list...

http://tinyurl.com/jcolwell-usedlens-checklist



Feb 27, 2013 at 06:40 PM
trueimage
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p.1 #3 · p.1 #3 · How to check a lens in the real world?


good idea. I capture most of that in a google drive spreadsheet, after the fact. I'm wondering what the best way to test the optics are in a "real world" situation, instead of bringing rulers and charts etc...


Feb 27, 2013 at 07:08 PM
snapsy
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p.1 #4 · p.1 #4 · How to check a lens in the real world?


trueimage wrote:
good idea. I capture most of that in a google drive spreadsheet, after the fact. I'm wondering what the best way to test the optics are in a "real world" situation, instead of bringing rulers and charts etc...


I'd research what the lens-standard is for IQ for both the center and corners, for both MFD and infinity, and shoot photos and review them @ 100% on a laptop I brought with me. I'd also check for decentering, again both at MFD and infinity.



Feb 27, 2013 at 07:17 PM
jcolwell
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p.1 #5 · p.1 #5 · How to check a lens in the real world?


trueimage wrote:
good idea. I capture most of that in a google drive spreadsheet, after the fact. I'm wondering what the best way to test the optics are in a "real world" situation, instead of bringing rulers and charts etc...

snapsy wrote:
I'd research what the lens-standard is for IQ for both the center and corners, for both MFD and infinity, and shoot photos and review them @ 100% on a laptop I brought with me. I'd also check for decentering, again both at MFD and infinity.

+1

That's exactly what the last part of my Used Lens Checklist is for:

Resolution relative to lens: __________________ near: _______ far: ______

Take a known lens with you, which the tested lens is relative to. Take a few near and far shots with your 'known' lens and then take repeat photos of the same subjects with the new lens. Your expectations for IQ performance of the new lens relative to the known lens should be clear, in advance.

I've found you can often make a valid comparison by inspecting magnified images on the rear LCD, but a notebook would be better, especially if you compared RAW files.



Feb 27, 2013 at 09:06 PM
Access
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p.1 #6 · p.1 #6 · How to check a lens in the real world?


Listen to it, listen to the AF operating, aperture changes etc. and make sure it doesn't squeak or sound like anything is binding inside.


Feb 27, 2013 at 09:20 PM
 

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mohoyt
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p.1 #7 · p.1 #7 · How to check a lens in the real world?


You could check for particles/dust/fungus etc. in the lens by stopping to ~f/22 and shooting the sky, or a white light. Though that could also reveal dust on your sensor...


Feb 27, 2013 at 09:21 PM
mpmendenhall
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p.1 #8 · p.1 #8 · How to check a lens in the real world?


Bring a bright LED flashlight. Looking into a lens while shining a flashlight through from the opposite side (slightly off-angle, so you aren't staring straight into the light), will light up all sorts of scary stuff --- dust, fungus, fingerprints, internal haze, separation, etc. Check several of your own "known good" lenses first this way, so you know what to expect --- if you aren't used to the fact that nearly *every* lens has a little dust and crud, then you might over-react to normal imperfections in a perfectly good optic.


Feb 27, 2013 at 09:34 PM
justruss
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p.1 #9 · p.1 #9 · How to check a lens in the real world?


Look it over with eyes.

Attach to camera.

Make a few photos.

Enjoy taking hundreds of photos with it-- smugly knowing that there are still people going through checklists and excel spreadsheets instead of using the thing they just paid for.

You did say real world, didn't you? Go shoot.



Feb 27, 2013 at 09:48 PM
molson
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p.1 #10 · p.1 #10 · How to check a lens in the real world?


justruss wrote:
Look it over with eyes.

Attach to camera.

Make a few photos.

Enjoy taking hundreds of photos with it-- smugly knowing that there are still people going through checklists and excel spreadsheets instead of using the thing they just paid for.

You did say real world, didn't you? Go shoot.



+1




Feb 27, 2013 at 10:01 PM
jcolwell
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p.1 #11 · p.1 #11 · How to check a lens in the real world?


I agree completely with justruss and molson. The "just go out and use the damn thing" school of thought is by far the best way to go, but only when you know what to look for, and you know how to do it.

In fact, I haven't used my checklist in many years. That's because I've bought, sold, and especially used enough lenses that I don't need a check list, anymore. My experience-based intuition generally serves me very well. OTOH, when I started doing this buy/sell/trade-up stuff way back in the old days, I needed all the help I could get. Some say, I still do.

IMO, people with relatively little experience in doing this, don't have enough practical experience to have reliable intuition. "Make a few photos" is fine, if you know what to do, and how to evaluate the results. Otherwise, it's difficult to make the right decision from "just go out and shoot", if you haven't done it before.

Would you fly on an airline that doesn't use checklists, because their pilots 'know how to do it'?



Feb 27, 2013 at 11:12 PM
Zenon Char
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p.1 #12 · p.1 #12 · How to check a lens in the real world?


For sharpness go to the zoo and find some birds. Eyes, beaks and claws tell the story. My standard for every new lens or camera.


Feb 27, 2013 at 11:23 PM





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