How can dust get inside a weather-sealed internal-focus lens?
Asked 1/15/2019
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I found a used Nikon 70-200mm VR II at a good price, but the seller says there is a little dust behind the front element. Since this is a weather-sealed, internal-focus lens, how could dust get in there?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
2
Some possible reasons:
- Intense environment (ex: The beach... especially bad if you change the lens on site)
- Poor storage (dusty bag)
- My Favorite : Zoom/Focus pump effect ! Even if it is sealed, a lens is not "a partial vacuum" ! The volume is changing, thus there is air going in and out !
For example : A lens like this old push-pull Canon Zoom can be "weather-resistant", but with such a MASSIVE push-pull displacement, there is a lot of air entering IN the lens.
The newer version of this lens can stay cleaner, because many more moving parts are staying in the body. At the other extreme, a typical 70-200 2.8 Zoom like this one will not move externally at all, and thus stay cleaner.
Most lenses will at least vary on volume with focus (even primes), thus having a problem with what is in the air around them.
The lesson here: Don't play with your zoom in the sauna !
Originally by user45742. Source · Licensed CC BY-SA 4.0
user45742
7y ago
0
Generated from our catalog & community — verify before relying on it.
Weather sealing reduces dust and moisture entry, but it does not make a lens airtight or a vacuum. Air still has to move in and out as internal groups shift during zooming or focusing, because the internal volume changes. That “pump” effect can carry fine dust inside over time.
Dust can also get in from use in harsh environments such as beaches or other dusty locations, or from poor storage in a dusty bag or room. Internal-zoom designs like a 70-200mm f/2.8 generally stay cleaner than lenses with large external barrel movement, but they are still not immune.
So a small amount of dust behind the front element is normal on many used lenses and does not necessarily mean the lens was abused. The key question is whether it affects image quality, which small internal dust usually does not.
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UniqueBot
AI7y ago
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