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05/30/2006 03:53:01 PM · #1 |
The other day I paid $26 to take a taxi out to a beautiful lighthouse and back while on my honeymoon. My new wife wandered down to the beach exploring. I stayed at the lighthouse with the intention of taking some pictures of her in the distance with my 70-200mm f/2.8 IS
As I was shooting the view started to get a little duller. I was like "huh". Then I realized it was getting foggy. So I looked at the polarizer cap I had to see if that could be it. Took that off and it was fine...no fog on the interior of the lens either. I was like *crud* it must be fogging inside the camera. I decided to try another lens expecting to see just fog. So I popped my Tamron 28-75mm on my 20D and saw beautiful clarity. *crap* The problem is my 70-200mm again. So I look closely at the lens again and realize the fog is inside the lens. WTF???
(It did clear up by the next morning.)
Is this normal? Okay, I admit, it was fairly warm day between upper 80's low 90's....but it was not off the charts. And this is supposed to be a professional weather sealed lens. I mean, what sort of lens does a professional photographer use in Africa?
So anyways....has anyone else had their 70-200mm or other lens fog up inside? is this just a fluke? common occurrence? nothing to be worried about? or should I be concerned and contact Canon? (which I am inclined to do but don't want to be naive and told "of course lenses occasionally fog up on the inside when shooting outdoors in summer").
- Jason
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05/30/2006 04:06:46 PM · #2 |
ooh, sounds nasty! if both lenses were from the same bag then I'd be inclined to send it to Canon (especially if you can recreate the problem) thats not a cheap lens and if there is a problem with the weather sealing you need to get it fixed, you could always test the weather sealing by popping it in a pan of water (on second thoughts!)
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05/30/2006 04:17:50 PM · #3 |
Did you perhaps have the lens outside for some time, then took it inside an air conditioned space, then back outside for the lighthous shoot? Here's why I ask...
If the lens was exposed for a long period to outside environment where it was hot/humid, then was brought into an air conditioned environment, it' possible that condensation formed inside as the lens body cooled, but before enough dry air was exchanged for the moisture to dissipate. Then, when you took the lens back out, the condensation was already present. If the lens was cold, though, I'd have expected condensation to form on the outside as well. It might not, if the outside of the lens had wamed above the dew point.
FWIW, no amount of weather sealing will keep air from being exchanged. If kept in a humid environment, the humidity inside the lens will come to equilibrium with the surrounding air. |
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05/30/2006 04:50:51 PM · #4 |
Actually, the climate I was in was fairly dry, actually I was in a desert like island (Aruba).
The camera had been stored/bagged in the hotel which was air conditioned to around 70 degrees earlier in the day. But I had been out for a while. So the lens was not cold.
I've had those experiences moving between indoors/outdoors and having a lens fog on the exterior. But both my Tamron and Tokina lens (much cheaper quality) were fine.
So if you call a desert isle humid, that might be it. But for some reason I don't think all the cactus would agree.
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Of note,...this lens has been to the shop a couple of times now. So it's been opened up a few times. I am wondering if moisture could have been in there. And then the effect of the bright sunlight coming thru the lens caused it to vaporize inside the internal elements?
Message edited by author 2006-05-30 16:53:13. |
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05/30/2006 05:43:11 PM · #5 |
Weather sealed dosn't mean air tight.
_Any_ lens or other complex bit of equipment that has high thermal inertia will get condensation ocasionally, unless it is actually air-tight. In the case of a lens this potential is actually increased by the sealing because the lens will not equalise the humidity as quickly as a cheap plastic consumer lens.
With a good filter and a 1D body the 70-200 is pretty close to air tight, but it can't be totally air tight, that would be very difficult to achieve with all the switches/buttons etc.
If the lens is at 25 degrees (C) and 70% RH and you go to an area that is 35(C) and lower humidity with the lens in a padded (insulated) bag the slightly more moist ait is trapped inside by the sealing until you whip the lens out...
Because the external components warm up first (front element & barrel) the moisture goes to the coldest bits of the lens, which unfortunately is the middle of the elements.
There are a couple of ways to get around it.
Carry lots of desecant in your camera bag, and dry it regularly, and if you know it's going to be hot/dry where you're going, leave the top of the camera bag open, so the lens can 'vent' the moisture during the trip there.
I have four large desecant pouches in my camera bag, and often travel with the 70-200 mounted on the camera, on the seat beside me, as it seems to be the worst for doing it. (And mine is not sealed, it's the non-IS ver). The 24-70 will also do it occasionally.
Something else I've seen is a chap who drilled 10mm holes in the rear cap, and glue a small bit of coffee filter over the hole so the lenses can 'vent' in transit to equalise humidity. That was on big L primes, but would work equally well on your 70-200.
Basically if you're storing the camera anywhere (hotel/plane/home) where the humidity is higher, and temperature lower than where you're taking photos, there is always a possiblity of fogging. The larger mass of glass (bigger apeture) and more substantial the lens is, the greater the possibility due to the thermal inertia of the guts of the lens. (They bits don't change temperature quickly)
Just my 2c worth.
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05/30/2006 06:25:47 PM · #6 |
So the sunlight hitting it was just a catalyst?
It took a few hours before it cleared and I could use it. |
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05/30/2006 09:10:22 PM · #7 |
Originally posted by theSaj:
So the sunlight hitting it was just a catalyst?
It took a few hours before it cleared and I could use it. |
The sun hitting the lens body would warm up the outside, increasing the differential between the temperature of the body and the internal glass elements.. That would cause the moisture to appear on the elements.
Taking the lens off, and leaving it somewhere in open air with the rear cap loose or completely off would probably have sped up the de-fogging.
Basically water vapour / moisture migrates to the coldest place/air/object. So if the lenses are the coldest objects in the area, that's where the moisture goes. This wont clear up untill all of the lens is at the same temperature, allowing the moisture to re vapourise, and then escape through the rear end of the lens. (Yes, through the camera if it's mounted)
L series lenses are built from aluminum and magnesium, and have fairly heavy glass elements in them, meaning that it takes longer for them to warm up, so they take longer to equalize temperature, therefore longer to de-fog.
Cheers, Chris H.
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