Lens annoyances--fogging and defogging

[tab]

I would have the Canon lens checked out by Canon. Lenses will fog under circumstances that already been listed but they shouldn't fog on the inside nor should it take hours to defog. You obviously have moisture inside your lens otherwise that wouldn't happen. When a lens fogs on the outside it's because the lens is cooler than the ambient temperature. If there is moisture in the air it will condense when it hits the cooler glass of the lens. The air inside the lens should be about the same temperature as the glass and should warm up a little faster than the glass but not enough to cause instant fogging unless the outside air is freely displacing the air inside your lens. I live down south so I have alot of experience with lenses fogging when I take them out of an air conditioned car or house into the hot humid outdoors. But when I have had them fog it was always on the outside glass and only lasted until the temperature gradient decreased. I would keep the rear cap on though.

[Clemmie]

The fog around the outside, leaving the center clear - coupled with the extreme persistency of the fogging - indicates to me the possibility of the lubricant seals being breached.

Have these lenses EVER been left in a hot car? Or laying out in the sun for several hours? Extreme overheating can cause it.

May be time for shop care.

[another view]

Something doesn't sound right here, I'd get the lens checked out too. If you use equipment in very humid conditions (or you're caught in a downpour, etc), take the gear home when you're done with it and let it dry out thoroughly before putting it back in the bag. I take both caps off of lenses, take all the stuff out of the camera bag, open up the tripod and anything else I can do to make sure everything's completely dry before it gets loaded in the bag again.

I've had lenses fog but only a few times. It's either been outside late at night when everything starts getting a layer of dew (can't do anything about this one) or because I didn't let a cold lens warm up enough before using it (like outside in the winter, then brought inside). Shouldn't happen that easily - as in the case of the Canon lens.

[VanessaN]

Thanks for everyone's help so far. Yes, I know the *outer* side of the lens will fog when going from cold to hot or humid or vice-versa, and this part is correctable with wiping until the camera adjusts, but it's the inner side of the glass that has been the problem.......and the thing is, is that I was totally not expecting it to happen on Saturday, since I got to the track at 7am, took some pictures (before security told me not to) of early am horses in training, as well as some front shots of the track entrance.

It was not cold, not hot, since I had been up that morning (had spent 2 hours on a PA bus from Philly, and 8 hours before that on a Greyhound bus from NY. And before that it was in my apartment, which has no airconditioning at all.

So after 7am I put the camera back in the bag where it sat around (outside the track) doing nothing until 9:40am, when I went back with the owner to the stables. I took a whole roll of her horse with the Canon lens without incident, outside the barn, then led her horse back in the barn and stood there for a while, then went outside and up a flight of stairs to the track. If it wasn't around my neck it was in my bag, and the bag itself had been in external and/or non-drastic elements for at least 3 hours.

The bag has not been subject to any downpours lately. And, the lens was fine with the first roll I shot. There was no discernable temperature change from climbing one flight of stairs to the track. It was breezier up there.

So, there's probably some damage, huh? (sigh) And I should send it directly to Canon? How much does this usually cost, anyway? Someone mentioned a breach--is this only caused by very hot temperatures? I have never left it outside for several hours in direct sun nor in a hot car (don't have a car, actually). I have been out for hours at a time, but it is usually in my bag, or, around my neck for extended periods if I go to the zoo (but then I am usually using my 100-400 Phoneix almost exclusively)

Thanks,
Vanessa