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what is the degree (cold) below which causes condensation


markfields

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In colder weather, using a camera outside and bringing it inside to a warmer envionment,

what otuside degree is the 'breaking " point that causes condenstation if you don't put a

camera in a bag when bringing it in. I figure it has to be below 40? Is it simply a matter of it

being 32F or below. I want to know what the safe degree point is(and above) where you don't

have to worry about condensation.

 

Many thanks,

Mark

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Sorry Mark, it's not that straight-forward. The dewpoint depends on the relative humidity and the temperature of the air. Generally the easiest way to figure it out is to use a psychrometric chart. An example can be found here:

 

http://www.sp.uconn.edu/~mdarre/NE-127/NewFiles/psychrometric_inset.html

 

To get the dewpoint, find the air temperature on the bottom edge, follow it straight up until it hits the curve for the room relative humidity, then draw a line to the left horizontally; wherever the line intersects the last curve (the 100% relative humidity curve) is the dew point. If your camera is colder than that, the moisture in the air will condense on it.

 

As an example, if the room temp is 70 deg F and the relative humidity is 50%, then the dew point is just below 50 deg F.

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Mark, it's not an absolute temperature; rather, it's a matter of the dewpoint inside, and dewpoint is a function of the relative humidity. If your cold camera is below the dewpoint of the warmer inside air, it's likely to cause condensation when you bring it in. For an explanation of dewpoint, Google it.
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Forget the meteorology and math of it. If it's substantially colder outside than it is inside

(like in the Winter), cover yourself with simple and cheap insurance. Put your camera/lens

inside a freezer bag when you come back inside and let it acclimate for an hour or two

before opening the bag. Better yet, leave the camera dn glass in your car and bring the

batteries and memory cards inside while everything else stays at temperature.

 

It's only the warming you need to worry about - not the cooling.

 

You can also do a simple test - take something like a heavy pot that's made of metal and

set it outside for a few hours, then bring it in. After a few minutes look to see if there's

ocndensation. You now have a benchmark.

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As Jerry and Peter said, there is no absolute temperature above which you're safe from

condensation. Any time your camera is colder than the dewpoint of the air surrounding it,

water will condense out of the air.

 

And despite what G.C. says, you can potentially get condensation when you bring a warm

camera into cold air: if the interior of the camera or lens contains warm humid air, water may

condense out of THAT air onto interior surfaces when the camera cools (never happened to

me in either Alaska or Antarctica but it is possible).

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I think it has to do with humidity and the amount of water vapor in the air more than temperature. When I lived in the San Francisco Bay Area, there was nothing more difficult to use than graduated neutral density filters. on windy days at the ocean which was most days they'd fog up like crazy. Half the time I couldn't even tell thru the viewfinder but would find out later upon closer inspection at home. i'd go to the waterfalls up there and I would be sweating from the humidity under the thick forests then i'd bring out a polarizer and that would be fogged up in addition to the lens underneath it. id' wipe it and the result would be worse because tiny water drops would be showing up in the images.

 

nowhere else I've shot in this country have I had problems with fogging so far. i don't have any answers but I just kept shooting through it and hoped for the best.

 

www.rwongphoto.com

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<I>I think it has to do with humidity and the amount of water vapor in the air more than

temperature.</i><P>

 

You are talking about humidity, the amount of water vapor in the air, and temperature as

if they were three unrelated parameters. Humidity is defined as the amount of water vapor

in the air. The amount of water vapor air (or any gas) can contain is strongly influenced

by temperature -- the higher the temperature, the more water vapor can be contained in a

given volume of gas. <B>Relative</b> humidity is just the fraction of the maximum

water vapor content at a given temperature; for example, a relative humidity of 50% means

the air holds 1/2 of the maximum content of water vapor possible at that temperature.

The same air, with the same water vapor content, will have a lower relative humidity if you

raise the temperature, and a higher relative humidity if you lower the temperature. If

relative humidity gets to 100%, the air is completely saturated with water vapor, and at any

lower temperature,

some of that vapor will condense into droplets of liquid water (that's how fog forms,

among other things).

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