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05-06-2011, 03:44 PM   #1
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Weather sealing and air-pumping zooms

What happens with the air in a weather sealed camera + lens system when the lens is being zoomed? Air has to go in and out of the camera then, or a pressure difference would be created. Does anyone know how this happens? Perhaps there is a little vent hole, with a filter in it, or does air just slip by the seals?

There would be the same question for any compact camera - I have used compact cameras and carried them with me everywhere for years, and I have never had any occurrences of dust on the sensors in those, and they also must pump air since they have zoom lenses.

This question is purely out of curiosity .

05-06-2011, 04:47 PM   #2
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If I am not mistaken, WR lenses are all internal zoom meaning the barrel doesn't change length. So the air volume internally would never need to change. Besides, the components are strong enough to handle the slight pressure change that could occur.
05-06-2011, 05:08 PM   #3
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QuoteOriginally posted by AOShep Quote
If I am not mistaken, WR lenses are all internal zoom meaning the barrel doesn't change length. So the air volume internally would never need to change. Besides, the components are strong enough to handle the slight pressure change that could occur.
Actually, the only WR lens that has internal zooming is the DA*50-135. All the rest of the zooms (DA*16-50, DA*60-250, 18-135WR, 18-55WR, 50-200WR) change length as you move from one focal length to another.
05-06-2011, 06:34 PM   #4
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QuoteOriginally posted by hjb981 Quote
What happens with the air in a weather sealed camera + lens system when the lens is being zoomed? Air has to go in and out of the camera then, or a pressure difference would be created. Does anyone know how this happens?
Very good question! I have often wondered about this myself.

05-06-2011, 07:01 PM   #5
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I've never had a camera explode ( or implode ) as a result of air pressure differences. So It's not something I've ever worried about.

If you are really worried peace of mind might be gained by removing the lens from the camera while zooming.
05-06-2011, 07:08 PM   #6
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QuoteOriginally posted by dgaies Quote
Actually, the only WR lens that has internal zooming is the DA*50-135. All the rest of the zooms (DA*16-50, DA*60-250, 18-135WR, 18-55WR, 50-200WR) change length as you move from one focal length to another.
Guess I didn't do my homework before responding. I'm also a bit disappointed that they are not all internal zoom.
05-06-2011, 07:56 PM   #7
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The Canon G-series (I had a G9) suffered badly from this syndrome due to the extra zoom length of the barrel. Problem was, Canon never admitted there was an inherent design fault and wouldn't own up to cleaning the sensor as part of the warranty.

Not sure of the current line of G if that was ever addressed but I'll never buy a G-series again due to this issue.

Here's a very long thread on the issue...

Flickr: Discussing G9 sensor dirt? Lens? in Canon PowerShot G9
05-07-2011, 04:22 AM   #8
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Er....

QuoteOriginally posted by dgaies Quote
Actually, the only WR lens that has internal zooming is the DA*50-135. All the rest of the zooms (DA*16-50, DA*60-250, 18-135WR, 18-55WR, 50-200WR) change length as you move from one focal length to another.
I recently bought the K5 with the two WR kit lenses; 18-55 and the 50-200mm. Of these the 50-200 changes length when zoomed and the 18-55 does not appear to change length. However I am no expert about these things, so maybe you are right.

To the OP, I have not been affected by any problems with air pumping or differences between air pressure inside the lens and outside with either lens.

I also have a Canon G10 and have not had any problems with air pumping with that.


Last edited by waxsage; 05-07-2011 at 04:24 AM. Reason: Adding information
05-07-2011, 04:42 AM   #9
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I wouldn't think the expansion/contraction issue would affect anything structurally, since we don't feel any resistance when zooming. If it were building that much, the lens would tend to suck back together and get shorter as we zoomed it longer. So that leads me to believe that the pressure/vacuum created would be being released somehow. I think this is the point of contention - HOW is it released, and if so, does that lead to a point where dirt/moisture can get in? I would hope, since these are designed to be water resistant lenses, that a method has been designed in that would filter the dust/moisture at a controlled location so it doesn't cause problems.

Is anyone willing to tear apart their * lens in the name of curiosity? I'm sure that there aren't that many parts...
05-07-2011, 05:20 AM   #10
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QuoteOriginally posted by waxsage Quote
I recently bought the K5 with the two WR kit lenses; 18-55 and the 50-200mm. Of these the 50-200 changes length when zoomed and the 18-55 does not appear to change length. However I am no expert about these things, so maybe you are right.
The 18-55WR doesn't change length very much. It's actually it's minimum overall length around the middle of the focal length range (~30mm) and it only expands about 3/8" at each end of the range.
05-07-2011, 10:18 AM   #11
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QuoteOriginally posted by hjb981 Quote
What happens with the air in a weather sealed camera + lens system when the lens is being zoomed? Air has to go in and out of the camera then, or a pressure difference would be created. Does anyone know how this happens? Perhaps there is a little vent hole, with a filter in it, or does air just slip by the seals?

There would be the same question for any compact camera - I have used compact cameras and carried them with me everywhere for years, and I have never had any occurrences of dust on the sensors in those, and they also must pump air since they have zoom lenses.

This question is purely out of curiosity .
Wow, you are lucky, every compact camera I owned eventually got dust inside until I got the Pentax Optio W's.
05-07-2011, 11:49 PM   #12
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QuoteOriginally posted by dgaies Quote
The 18-55WR doesn't change length very much. It's actually it's minimum overall length around the middle of the focal length range (~30mm) and it only expands about 3/8" at each end of the range.
You're quite right! I've been using the 50-200 for a few weeks and forgot about that change in length for the 18-55. Fortunately, no problems as far as I am aware about air-pumping issues, maybe because I haven't used it so much.

If someone had good hearing, I don't anymore, would they be able to hear the location of where the air equalises? Perhaps using a stethoscope...?
05-08-2011, 12:24 AM   #13
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Come on, WR lenses are weather resistant, not air tight!
05-08-2011, 01:30 AM   #14
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QuoteOriginally posted by sabarrett Quote
I wouldn't think the expansion/contraction issue would affect anything structurally, since we don't feel any resistance when zooming. If it were building that much, the lens would tend to suck back together and get shorter as we zoomed it longer. So that leads me to believe that the pressure/vacuum created would be being released somehow. I think this is the point of contention - HOW is it released, and if so, does that lead to a point where dirt/moisture can get in? I would hope, since these are designed to be water resistant lenses, that a method has been designed in that would filter the dust/moisture at a controlled location so it doesn't cause problems.

Is anyone willing to tear apart their * lens in the name of curiosity? I'm sure that there aren't that many parts...
On my K10D I can feel air blowing out of the OK button when I zoom out with my 16-50mm. The weather-sealing is obviously not perfect, but I've used this setup in pretty adverse conditions without issues, so I'm happy with it.
05-08-2011, 01:06 PM   #15
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WR lenses are resistant to weather, meaning water and dust have a heck of a time getting in. It does not mean they are waterproof (therefore airtight) and can be submerged (without a housing anyway). There has to be some amount of air that comes from the outside of the lens, so long as the lens changes length. Perhaps internal zooming lenses are airtight, but if it extends, it's not. Easy way to check would be to take a DA* 50-135 and submerge it, it if bubbles, then its not airtight, though that'd be a colossal waste of a great lens as my money is on it bubbling... Any lens will eventually have a small amount of dust work its way inside, but usually on lenses such as these, the dust that gets inside will be too small to have an effect on optics and it will take longer for the dust to end up inside than on a not sealed lens.
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