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 Lens Fog (Planning) 
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Joined: Sat Jul 17, 2010 12:26 pm
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Post Lens Fog (Planning)
I was going to do some research to answer my own question but I thought I would make it public to help out readers as well as myself. What is the science behind condensation on the lens? At what temperature(difference?) will it fog, and how do we plan and prevent this properly and efficiently. (hand warmer in a sock around lens body??) On one of my night TL it was fine until the clouds went away and apparently changed the temp causing lens fog.


Sun Aug 22, 2010 4:39 pm
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Joined: Sun Jul 18, 2010 9:59 am
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Post Re: Lens Fog (Planning)
The condensation is from the temperature of the lens reaching the dew point in the air, I'm pretty sure. I get this as well and can't really answer the rest, I'd like to know as well.

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Sun Aug 22, 2010 7:41 pm
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Location: Antarctica/California/New Zealand
Post Re: Lens Fog (Planning)
There is a free iPhone / iPod app for calculating it, but you need to know what your temperature and humidity is first.

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Sun Aug 22, 2010 9:10 pm
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Joined: Tue Aug 26, 2008 3:30 am
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Location: Sydney, Australia
Post Re: Lens Fog (Planning)
Not sure of the calculation but this is a practical solution :http://timescapes.org/phpBB3/viewtopic.php?f=18&t=2623&p=16780#p16780


Sun Aug 22, 2010 9:12 pm
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Post Re: Lens Fog (Planning)
I also read somewhere that you could place your lens in a sealed bag and leave it outside so it equalizes temperature before you take pictures. anyone have success with this method? but what happens when the temp takes a sudden plunge afterwords?


Mon Aug 23, 2010 2:28 am
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Joined: Sun Jan 31, 2010 12:47 pm
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Location: UK
Post Re: Lens Fog (Planning)
Baade,
The sealed bag method is very useful in both directions. I've mostly used it when bringing electronics/camera's inside from as low as -20c to room temeparture. You need to have as little air in the bag as possible.


Mon Aug 23, 2010 6:43 am
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Joined: Wed Nov 18, 2009 8:09 am
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Post Re: Lens Fog (Planning)
baade wrote:
I was going to do some research to answer my own question but I thought I would make it public to help out readers as well as myself. What is the science behind condensation on the lens? At what temperature(difference?) will it fog, and how do we plan and prevent this properly and efficiently. (hand warmer in a sock around lens body??) On one of my night TL it was fine until the clouds went away and apparently changed the temp causing lens fog.


Condensation is one thing, precipitation is another. You can park 2 cars outside, one under a carport and the other out in the open. IN the morning, one will be covered in dew, the other will not.

Try placing your camera under a carport-like structure.

But if you're really serious, you will want to invest in some kind of environmental enclosure.

bogiesan


Wed Sep 01, 2010 2:19 pm
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Joined: Wed Sep 15, 2010 1:39 pm
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Post Re: Lens Fog (Planning)
My understanding is that as ambient temperature approaches the dew point, the atmosphere is so moist that condensation forms, ie.fog.

During a recent summertime overnight timelapse session, I placed a fan near the camera and aimed it directly at the lens whilst out of view. Everything was practically dripping around the gear, but the lenses were clean.

I hope this helps.

best,
s.


Wed Sep 15, 2010 1:47 pm
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