How do I prevent condensation on a lens when outdoors?

Question

I was attempting a time lapse the other evening, outdoors and after a warmish sunny day, with a fairly cool air temp. I set my camera up and set it clicking away and left it for about 3 hours. Most of the time when I checked on it it was perfectly fine. But when I finally went out there was loads of condensation on the lens, glass and barrel, and on the back of the camera too.

I had set my camera up a few hours before it went dark, just to get the framing right, so I assume it was at the ambient temperature. It wasn't in the sunlight, so it could only have cooled down from when I set it up.

Is there a reliable and simple way to stop this happening? I hope so, as it must be a fairly common occurrence. Main reason is I don't want a damp camera as it will do it no good. Second reason is that it will ruin my timelapses!

Answer 1

You're right, the problem with heating the environment is that it can produce "heat waves" which show up in your photographs if you're not very careful. All in all it seemed like bringing a heater (propane, or otherwise) was something that I was going to have to monitor and fiddle with a lot, so I didn't ever go down the path of trying to keep the environmental temperature above the dew point... One of my goals when doing time lapses is to be as automated as possible, so the heater didn't 'pass the test' for me in that regard.

As you might imagine, this is a very common problem in the astronomy world, so it's one area where we can simply borrow liberally from their techniques (and their equipment as well).

1. Lens Sleeve: On the 'low cost' end of the scale is simply wrapping the front part of your lens. I went out and bought some neoprene and fashioned my own 'lens sleeve,' but if you're more interested in purchasing something, telescope accessory manufacturers such as Orion make similar products...

2. Heat Strap: One step up the scale (in both sophistication and complexity) is to use a heating strap. With a heating strap you simply strap it to your lens near the front element and it keeps the glass warm enough that condensation can't form.

3. Multiple Solutions: If you're expecting really wide temperature swings (depends on your region... Where I live in the spring and fall we can experience 20 to 30 degree swings between day and night), a single heating strap may not be enough. I've had some success with the lens sleeve plus the heating strap, but I finally did bite the bullet a couple years ago and bought a multi-channel prevention system so I could keep the entire lens warm (not just at the front element). Carrying the idea to its extreme, I've recently done some full-winter day-to-night timelapses here in the northwest where I've been using a full neoprene 'suit' for my entire camera and lens (made myself, cut the pieces from an old wetsuit and sewed them together like a 8-year-old cub scout trying to earn his leatherwork badge at camp! It ain't pretty, but it works...) and a multi-channel heating system together, which worked like a champ. Obviously the downside to this type of solution is its complexity, but for all-night timelapses I'm already hauling car batteries and motorized dolly platforms, so adding another powered item didn't seem like such a big deal. :-)

_{(NOTE: I'm not affiliated with Orion Telescopes, and there are other companies that manufacture similar products... Just a user of their products.)}

Answer 2

Normally, condensation occurs in a humid environment as a result of the difference of the temperatures of the air and the object on which it occurs. The problem here appears to be a more or less rapid drop in temperature I guess - one solution might be the use of a see-throuh rain cover, or a large enough ziplock bag with appropriate cuts, applied before taking the camera out of doors to minimize the humidity trapped in it. Otherwise, the same humidity will still condense within the rain cover itself instead of in the camera just like when one uses a rain cover in cold weather with a warm camera.

Another, not as practical, but effective solution might be to regulate the temperature around the camera, but isolating it from humidity is the more guaranteed solution, even if it is only applicable in very few situations...

Answer 3

A lens hood will not solve the problem. If you can't afford to make one of the small resistive 'dew-zappers', you can use the hand/mitt warmers that they sell in hardware stores. I surround the lens hood with two of these. I hold it to the lens hood with a cut-off piece of old sock. These hand warmers last all night.

Answer 4

Check the dew point temperature. If your lens is at or below the dew point for whatever the temperature outside is, dew will collect. Manufacturers can make electrically heated windows much like the heated windows in the F-117A and other aircraft. It uses a thin film (ITO) with current flow through the lens with several watts/sq inch dissipated. Probably, unless your lens is on a spy satellite, its beyond the affordability of most of us.