how to combat dew when using camera gear for long exposures near dewy environments?

[erotavlas]

Hi does anyone have advice on how to combat dew forming? I'm into long exposure photography, mostly at night and near lakes in particular I find dew to be a problem. Does anyone have recommendations on how to keep dew away? I usually always keep my lens hood on which sort of helps, but what about the other surfaces of the camera? Mine is not exactly weather sealed (Sony Nex 5N)

 

[KmH]

Astronomers use heaters to keep dew off their optics.
http://www.telescope.com/Accessorie...el-Prevention-System/pc/-1/c/3/sc/44/e/22.uts

How does dew form?

Dew forms when a surface cools through loss of infrared radiation down to a temperature which is colder than the dewpoint of the air next to that surface.

Dew most often forms on on evenings or nights when there are few clouds, since the greenhouse effect from clouds can keep surfaces from cooling by infrared radiation loss to outer space. Calm winds at night also contribute to dew formation because a windy night keeps the lowest layers of the atmosphere warmer, and also helps evaporate any dew that might begin to form on surfaces.

Dew is made of liquid water that has condensed from some of the contained in the air.

If the layer of air next to the ground also cools to the dewpoint temperature, then fog forms as well.

 

[erotavlas]

I was thinking this as well since I have a telescope, but I haven't purchased any dew shield or heaters yet.

I was thinking more about alternatives to those methods used for telescopes, since I want to remain as portable as possible

 

[grafxman]

Try some of the stuff on this list:

rain protection| B&H Photo Video

 

[Gavjenks]

Heating is pretty much the only way I think to keep water off during an exposure, as in to stop it from interfering with the image on your front glass. Rain protective gear will keep water out of your camera, but not out of the image. Unless you could somehow continuously replace or rotate out clear glass in front maybe?

 

[Murray Bloom]

I'd try putting a few of those cryogenic [?] hand warmers in the bag and firing them up one at a time or when needed.

 

[KmH]

cryogenic [?]

Cryogenic is cold storage, or the production of low temperatures by an endothermic chemical reaction.
Exothermic is a chemical reaction that makes heat.

 

[Murray Bloom]

Oh, of course! Exothermic, then.

 

[Karburn]

Perhaps a small battery-operated fan to blow across the gear? Not that you'd want to blow dust, etc. on the lens, but a light airflow might be enough to ward off the dew. Take extra batteries.

 

[amolitor]

I'd pop the camera in a suitably sized ziploc, cut a lens opening, and tape around that. That should handle the camera itself pretty well.

Dew does fall, to some extent, so protecting overhead will be some help for protecting the front of the lens element from droplets, as you have observed with the lens hood. Use a bigger "roof" structure than that even, if you can fabricate something.

Warmth will help with condensation. I rather like the hand-warmers idea. Warm the camera up pretty well before use, and then chuck a hand warmer into the ziploc to see if that will maintain the temperature out to the lens front element enough. You should be able to get the camera pretty darn hot without hurting anything. Quite Warm To The Touch should be fine, but too hot to hold comfortably is probably pushing it!

 

[grafxman]

If Canons get hotter than 104° F they may not work.

 

[Gavjenks]

If Canons get hotter than 104° F they may not work.

To prevent condensation, you only need it to be warmer than the air. So unless it's over 104 degrees at night or early morning in your area (virtually nowhere), heating will still work, although you may want to be careful about exact temperature.

Also, my cameras have worked in well above 104 degree heat (e.g., 95-100 degrees outside + direct sun beating down on a black camera for hours and greenhouse effect in the body, it was probably like 120 at least in there. Similar to a car). Canon might not have extended warranty protection to me, but that doesn't necessarily mean it actually stops working.

There's also the option of just heating the front of the lens and then protecting the body with plastic bags, as amolitor basically said. The front of the lens is not going to have the same sort of heat requirements at the body with all of its electronics and sensor. The lens front should work pretty well up until the gaskets start melting, pretty much. I wouldn't be surprised if you could heat the front element up to 200 or so (assuming your lens doesn't have its image stabilization or similar mechanisms right up at the front)

 

[astroNikon]

With Dew, In my earlier astrophotography days I used to just tape a thick piece of construction paper from the lens over the top of the body. This will prevent dew from falling onto the body, and you can just lift if up to do what you need to do. You can also roll up a piece as an extension of the lens hood (but check to make sure it doesn't impose on the image view width). I'm not sure how much it helped looking back ...

Overall heating is really the only good solution when there's alot of humidity. Any fans or heater can cause disturbances in the air which can hurt the sharpness significantly of a longer exposure.

 

[TCampbell]

To fend off dew, astronomers use both dew shields and dew heaters. The dew shield (basically an extra long lens hood) fends off dew falling out of the sky from above and the dew heater keeps surfaces warm enough so that water doesn't want to condense on your optics. But there is a trick to them....

You don't want to over-warm the lens otherwise you'll produce heat currents in a long exposure... imagine taking a photo while shooting through water with ripples on it... it'll ruin the photo and every shot will be soft.

So the idea is to use the coolest possible temperature you can get away with and YET still be just warm enough to fend off the dew. Often that temperature may only be about 5º warmer than the ambient air.

The dew heater system has two major components... you need a "controller" and then you need the heating strips. The heating strips typically have RCA type "tulip" plugs and they run on 12v "system" power (e.g. a 13.8v DC power source since 12v batteries seldom actually put out 12v.) The power to the strip is pulsed to control it's temperature. The controller handles the pulsing. I use a DewBuster controller which has two temperature probes on the scope. One probe measures the temperature of the ambient air. The other probe measure the temperature of my telescope. The controller has a dial to allow how much warmer the scope should be above the temperature of ambient air. I use Dew-Not brand dew heater straps.

 

[grafxman]

In May of 2010 I shot Tate's Hell in the Florida Panhandle. I placed the 7D in the trunk of the car and returned to the motel in Tallahassee. I removed the 7D, hooked it up to the computer and attempted, unsuccessfully, to download the photos. The camera would not come on until it cooled down. The same thing happen the next day. I don't know how hot the camera was but it was very warm to the touch.