How Dust and Damage on Lenses Affect Image Quality

This photograph was taken by a lens with some “obstruction” on the front element. Aside from the blurry patch of nastiness in the bottom portion of the frame, the rest of the image looks pretty decent. What do you think the “obstruction” is? A little dirt? A smudge where the photographer accidentally touched the front element? A scratch? The answer is a little closer to a scratch than a smudge…

Here’s the lens that shot the photograph:

Kurt Munger purchased a used lens off eBay, was ripped off, then decided to put it to use by doing some tests that no sane photo-enthusiast would do with their nice lenses. He dirtied and damaged the lens to varying degrees, then shot with it to see how image quality was affected.

Based on my un-scientific testing, I’d say there isn’t any noticeable reduction in image quality as a result of normal dirt, smudges and small scratches on the front element. My dirt, smudges and scratches presented here are clearly more numerous and larger than what I’d consider “normal,” but as I’ve shown, they have little effect on image quality.

Another interesting result of his tests is that completely removing the damaged front element actually turned the lens into a macro lens!

Here’s what you might want to take away from Munger’s sacrifice: don’t be too paranoid about getting dust or smudges on your lens or UV filter — they probably won’t affect your image quality much (if at all). Cleaning your lens too often or improperly is probably worse for your photos than the dust or smudges you’re trying to clean off!

Also, if you accidentally smash the front element of your lens beyond repair, try removing the front element completely instead of throwing the lens away. You just might have a nifty macro lens on your hands.

Dirty lens article [KurtMunger]

Image credits: Photographs by Kurt Munger and used with permission

  • David Todd

    Thanks To That Man Kurt

  • Nate Zimmer

    It’s largely depended on the F-Stop. A low F-stop like 2.8 will not show dust or lens damage¬†but a high F stop like F11 will show all the dust. I learned this the hard way recently after thinking it didn’t matter.

  • Jyve

    Sensor dust will usually play a big part in smudges too. To test, shoot a plain surface that takes up the whole frame, go down to your lowest f-stop and lowest ISO, shoot and you’ll see if you have ‘dust bunnies’.

  • Zulater02

    LensRentals did this a few years back. Interesting for sure.

  • Reatha Kenny

    Arghhh I just sold off a really scratched lens for peanuts. I wish I’d kept it now and just removed the front element, it might have made a nice macro.

  • Temple16

    “…instead of throwing the lens away (or trying to sell it on Ebay). You just might have a nifty macro lens on your hands.”

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  • ronbrinkmann

    Here’s another example of how much you can get away with (sometimes) and how it relates to f-stop: ¬†

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  • Celsochic

    Living and learning.

  • Anonymous

    Very cool!

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  • Harry Rose

    I just saw a canon Mk1 70-200 f2.8 with a damaged front glass going for peanuts on our E-Bay, Trademe. I should have bid on it.

    I still prefer film to digital as does Platon. I still prefer manual focus and the appature ring on the lens. I must be old.

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