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Regardless of weather sealing lenses will get dusty if they breathe. If any outside lenses move the internal volume of air must change and that means air is bei
by lmilcin 7y ago
Regardless of weather sealing lenses will get dusty if they breathe. If any outside lenses move the internal volume of air must change and that means air is being exchanged with the outside.
- IgorPartola 7y agoCouldn’t you make a lens with a vacuum inside?
- chongli 7y agoIt's pretty hard to make a vacuum with moving parts included in the wall of the chamber. The better your vacuum seal, the harder it'll be to move the lens elements and vice versa. And if the seal fails then you'll get a lot of dust inside.
- lmilcin 7y agoIf the lens does not breathe there would be no advantage (it can just be airtight without being vacuum) and if the lens breathes (ie changes internal volume) it means the motor would have to work against atmospheric pressure which would be extremely difficult in a lens to do reliably.
- penagwin 7y agoCounter question: Why not fill lenses with Nitrogen? I know outdoor cameras CCTV cameras do this (more so to prevent condensation from internal moisture).
- grozzle 7y agoYou'd still have to compress the nitrogen going one way to zoom, and pull the nitrogen against air pressure going the other way. Focus motors powerful enough to do that, plus including movable airtight seals to keep the nitrogen inside, would make the lens a serious chunk bigger, heavier and more expensive. The dust that gets inside from breathing while zooming rarely affects image quality to any meaningful degree. Excessive humidity can lead to fungus growing on the glass though, which really can ruin your contrast. It's normally good enough to keep your lenses in a box with some silica desiccant during summer to prevent that.
- mschuster91 7y agoThis lens, same as (for example) the SELP18105G (E-mount APS C 18-105mm/f4 Power Zoom) is fixed-length, meaning there is nothing moving on the outside.
- ijpoijpoihpiuoh 7y agoI don't think that necessarily implies that the inside will get dusty. For example, if the air intake had a HEPA filter with a sufficient lifetime, only particles smaller than the filter's rating would be able to enter the body of the lens.
- lmilcin 7y agoI suspect this is design tradeoff. First, hepa filters tend to block flow of air A LOT. Lens designers strive to get lenses to focus as quickly as possible. Any blockage of air would necessarily make it very difficult for the lens to breathe quickly. Second, dust particles in the lens do not affect the image nearly as much as you would think they do. Just look at this pic: https://www.lensrentals.com/blog/2008/10/front-element-scratches/ https://www.lensrentals.com/blog/2008/10/front-element-scrat...
- amluto 7y agoDo they at least have filtered air vents? Most hard disks (the non-helium-filled ones) are very carefully sealed except for a single vent that has a big filter on it.
- ianburrell 7y agoDust in a lens isn't a big problem. It really doesn't effect the image quality [1]. They had another tear-down to remove a fly from Canon 70-200mm [2], and it didn't make difference until stopped down. 1: https://www.lensrentals.com/blog/2011/08/the-apocalypse-of-lens-dust/ https://www.lensrentals.com/blog/2011/08/the-apocalypse-of-l... 2: https://www.lensrentals.com/blog/2019/04/removing-fly-from-weather-sealed-canon-70-200mm/ https://www.lensrentals.com/blog/2019/04/removing-fly-from-w...
- jimktrains2 7y agoIf there was no exchange it would create a pressure differential. I don't know how large it would be or if it'd matter though, but if it weren't large enough to overpower the mechanism or make it difficult to use, it could avoid purposely exchanging air.