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How can I test a new lens to make sure it is operating correctly? I found two similar questions with answers specific to things such as sharpness and focus, but I want to cover any and all possible tests for a new lens. What can I check for or do? What specific things do you do when you are inspecting a brand new lens from the manufacturer?

Related:

How can I/should I check the sharpness of my camera lens?

How can I determine if my Sigma 10-20mm lens copy is appropriately sharp and focusing right?

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Good question! :) –  rfusca May 20 '11 at 1:41
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I so want to say "use it" as an answer, but I don't want to sound like a jerk doing so. However, I think it's legit. In other words, don't expend effort on determining if it is "operating correctly" as it is meaningles, expend effort on determining if you like what you get from it. –  John Cavan May 20 '11 at 3:05
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@John Caven - Its not that I don't agree with you, but when I spend over $1,000 on a new lens, I not only want to see great shots come out of it, but I want to precisely test it before I show up at a paid event with it. –  dpollitt May 20 '11 at 18:21
    
@John I appreciate what you say, because it's easy to get too technical, but I have to agree with @dpollitt: I found the hour or so it takes to test a lens and review the results is worthwhile, because from then on whenever I use it I can visualize the effects of my choice of aperture and focal length on the picture quality (especially sharpness, contrast, and color). I know which lens to pick to get the most out of an opportunity and there's much less guessing and much less bracketing needed to get the pictures I envision. –  whuber May 20 '11 at 21:44
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and @whuber - Notice I didn't say how to use it, just that I said to use it. Just my take, real world means more to me, so my interest is in how it performs with real images and that's using it to me. It may be just an hour, but getting the lens into the situations you want to use it for is the real test that matters. –  John Cavan May 21 '11 at 1:07

3 Answers 3

up vote 21 down vote accepted

More than testing you should learn about your new lens. Although it is good to get some sanity checking first:

  • Set up a flat target with sharp details that can cover the field-of-view of your lens.
  • Set up your camera on a tripod pointing strait at the target.
  • Repeatedly autofocus on your target and see if you can improve accuracy by manual focusing. If it is off, then you'll have to micro adjust your lens (see questions on this site)
  • Once you got perfect focus, start shooting.
  • Take one shot at each aperture from the widest to the one stop beyond the diffraction limit. Say F/1.4 to F/16 on a modern DSLR.
  • Make sure each shot is taken with the self-timer and mirror lockup, preferable remote triggered.
  • Repeat above steps for various focal lengths from the widest to the longest.
  • Repeat all of the above using a blank completely uniform target.

Loot at all those photos and note:

  • How does sharpness change from the center to the corners?
  • See how the above changes for each aperture.
  • How does brightness change from the center to corners?
  • Take note of any apertures you would NOT be happy using.
  • Take note if there are focal-lengths you would NOT be happy using.

Then comes the subjective part. You need to judge if this is the quality you expect from such a lens. It is normal for lenses to by softer wide-open, some sharpen after 1/2 stop, some after 2. Personally, I find it easy to avoid certain apertures since I work in A-mode 95% of the time but I do not like having to avoid entire focal-lengths.

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Awesome answer, I really like how you take the holistic approach and cover not just testing, but becoming familiar with the new equipment. –  dpollitt May 20 '11 at 15:30
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FTR, the question on micro-adjusting lenses: photo.stackexchange.com/questions/1/… –  mattdm May 20 '11 at 18:14
    
very nice answer –  TheIndependentAquarius Mar 24 '12 at 1:09
    
What is a "flat target" for such testing? –  Raj More Jul 24 '12 at 14:48
    
Any object which is completely flat. You can of course buy pricey resolution and color charts but even a cereal box can do. –  Itai Jul 24 '12 at 17:06

Fairly comprehensive, but easy to follow tips.

How LensRentals.com tests lenses

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Great link, that looks like a huge asset. –  dpollitt May 20 '11 at 18:09
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could you please add summary of key points here so the valuable info would not disappear when the link stops working? –  Imre May 21 '11 at 0:56

Make the photos you bought the lens for. For each feature of the lens that is important for you, make a photo that utilizes it. Only you know why it is important to you, so you can construct the best test photo. For example, I really hate having color aberration around tree branches in front of clear sky, so I'd test for that.

Make sure the lens has an opportunity to show its best. Give your camera a secure support (sturdy tripod on level ground, legs as short as reasonable, central column not extended). Use a lens hood, avoid protection filters. Unless your scene has a lot of action, use mirror lock-up, remote control or self timer to trigger the shutter. Prefer contrast-detect focusing or make sure the phase detection sensors have correct micro-adjustment.

Analyze the photos and see if you are satisfied with them. If not, analyze if the bad aspects can be attributed to the lens, some other piece of equipment or your technique. Ask here if you're not sure.

Making the photos, you will notice any obvious deficiencies. No lens is perfect, no matter how much it costs. Engineered products are always results of a series of compromises. If the results look good, stop worrying and make more photos.

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+1 for stop worrying! Don't become a pixel-peeker who gets upset about minute details that won't matter in the real world. Rather look at the big picture. Only lens I ever sent back had a manufacturing defect so blatantly obvious it was apparent within a few minutes of mounting it, no need to see the pictures it produced even (which is a good thing, as this was pre-digital when processing and printing took days). –  jwenting Nov 14 '11 at 11:05

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