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Lens fogging up in the cold, how do you avoid this?

Mark Stephan , Nov 04, 2009; 08:09 a.m.

I went out last night to photograph the moon with my T90 and nFD 500 mirror lens and after setting up and attaching the lens to tripod and looking through the viewfinder it was fogged up. Temperature was in the mid 30's. I was wondering what you do to avoid this? Do I need to leave my gear out for awhile and let it get acclimated to the cold? Could this damage anything? Once the lens cleared up outside it fogged up upon return to the house, is this also an avoidable situation?


Carl Follstad , Nov 04, 2009; 08:20 a.m.

Similar threads have been posted in the past. Check this out:


Evan Goulet , Nov 04, 2009; 08:27 a.m.

Basically you need to let your lens equilibrate to the temperatures in which you plan to use it. Just like you get condensation on car windshield in these conditions, you will get it on your lens.
Your lens was warm when you took it outside, and the air inside the lens probably had a higher humidity than the outside air temperatures could support, hence you would get condensation on some of the elements when they cooled to outdoor temperatures. Once the condensation evaporates and the temperature/humidity inside the lens equilibrates with the environment the fogging goes away.
When you bring a cold lens indoors, the humidity from the indoor air condenses on the cold lens. Sort of like a drink with ice cubes sweats in the summer.
You can try storing lenses in a container with desiccant to keep the relative humidity inside of them low, while the temps equilibrate. From a photographic standpoint, allow time for equilibration before you need to use them so you don't miss any shots.

Peter Szwed , Nov 04, 2009; 04:52 p.m.

I had the reverse situation occur. All my gear was in the garage in anticipation of doing some night shooting. A warm front moved in with lots of humidity. As soon as I took off the caps, my lenses fogged because they were equalized to the colder temperature of the garage. I warmed everything up by wrapping them in a heating blanket for about a half an hour. You can also use a heat lamp or even the oven set on the lowest setting if you are very careful. If you only have a camera and one or two lenses, you could put them inside your coat and let body heat warm them up.
An uninsulated room, garage, shed, or even your car can work well to equalize in cold weather. Force equalization to a colder temperture is a lot harder. In the field, a cooler and some dry ice are your best bet. Regular ice could be used but has a good chance of introducing a lot of moisture to your gear. If you're at home, stick your stuff in the fridge. Most modern refrigerators are frost free. A freezer could get the temperture of your gear very low but, and this is a very big but, there is the danger of forming ice crystals on and inside your gear.

Peter Szwed , Nov 04, 2009; 04:53 p.m.

Sorry about the multiple posts

Alan Peed , Nov 04, 2009; 06:21 p.m.

When you are outside with the camera on a cold night, try to avoid breathing on the VF. The mositure in your breath can easily condense on a cold glass surface. You can wipe away condensation with soft, clean, dry cloth like a men's handkerchif.

After you are done shooting, the camera and lens will be cold. You do not want to take it directly into a warm place because moisture is very likey to accumulate on camera surfaces. Even on internal surfaces you can't get to. SO, put a cold camera and lens inside a plastic bag and seal it up so its airtight. A large Ziplock Bag works ok. Then bring the camera inside the house and just set it down out of the way. Leave it in the bag long enough for the camera and lens to slowly warm back up to room temp. The plastic bag will serve as a vapor shield and will prevent condensation from accumulating on the camera. After letting it sit for a while, then you you can take it out and store it in the normal place.

BTW, this type situation can also occur in the Summer, if you live in very warm and moist locale. IE, if you have the camera and lens stored in a very cool & dry air-conditioned office (temp is say in the high 60's), and then go out in the early morning on a warm & moist summer day, the outside moisture can immediately condense on your lens and fog it. In this case, you need a soft, clean, dry cloth to carefully wipe the lens to de-fog it. After a while, the camera will acclimate to the outside temps and it won't be a problem any more.

Mark Stephan , Nov 05, 2009; 05:28 a.m.

As always thanks for the great advice. I'll have to find a better alternative to the large zip lock bag though because some of my lenses wouldn't fit. I wonder if a well sealed garbage bag would also do the trick?

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