lens fog

[den9]

went out front of my house and did a 1 hour exposure of the stars. i put my lens in a ziplock bag and left it outside in the cold for a half hour, then i took the camera out of the bag and took the shot, came back and hour later to release the shutter and the lens was fogged up. how do i keep it from fogging on long exposures (40 degrees outside)

 

[ErectedGryphon]

Wrap the lens with pocket hand warmers.

Hand Warmers, Toe Warmers, Foot Warmers and Body Warmers from Grabber

 

[Derrel]

I would go the absolute other way...pull the battery out of the camera,and then put the camera in the refrigerator to get good and chilled....zip the camera outside really fast,and set it up and make the exposure.

 

[ErectedGryphon]

I would go the absolute other way...pull the battery out of the camera,and then put the camera in the refrigerator to get good and chilled....zip the camera outside really fast,and set it up and make the exposure.

You describe Cold Soaking...

Cold Soaking

During operation, digital cameras actually generate their own heat. With some early digital cameras, after continuous operation for a while the batteries became almost to hot to touch! Modern cameras are significantly more efficient and generate less heat, but if you can keep that heat in the camera (by not cold soaking it), you may have fewer cold weather related problems.

Cold soaking is leaving a camera out in the cold until every part is at ambient temperature - and it's likely to increase the probability of cold related problems. Since it can take quite a while for a camera to fully cool, if you only expose your camera to the very coldest temperatures when you're shooting, and put it in a pocket or a camera bag when it's not in use, you'll likely have fewer problems then if you leave it permanently hanging around your neck, fully exposed to the cold. It may not be that much warmer in your pocket or your camera bag but every little helps. See also the section "Hand Warmers," below.

One thing to avoid though is bringing a really cold camera under your coat, especially if you've been sweating and the air trapped under your coat is very humid. This can happen even in very cold weather if you have a highly insulating coat and you've been working hard, for example by walking though deep snow. A cold camera/lens in a humid environment can results in condensation of moisture on both the optics and electronics, which is something best avoided. (See also "coming in from the cold" below).

Source: Winter photography tips from Adorama Learning Center

 

[den9]

well i pretty much stuck it in the fridge when it was outside in the cold for over an hour, if i wiped the condensation off the lens would it stay off?

 

[KmH]

Not if the dew point was high enough.

 

[Flash Harry]

Never tried this on a lens but on a m/bike helmet visor a very small amount of washing up liquid smeared over the view area kept the fog at bay when breathing during cold weather riding, and I mean really cold, below zero. H

 

[tom123]

Did you use a uv filter? If yes, is it possible that you had moisture between the lens and the filter that caused the fog. Generally speaking, when the lens is warmer or exactly as cold as the air around it, you should not get fog.

 

[den9]

Never tried this on a lens but on a m/bike helmet visor a very small amount of washing up liquid smeared over the view area kept the fog at bay when breathing during cold weather riding, and I mean really cold, below zero. H

if washing up liquid refers to soap that does work, i use it for my shaving mirror, i just dont think i could do that to my lens. im going to try it again tonight.

 

[KmH]

Liquid dish soap specifically. One small drop applied with a lens tissue.

 

[Josh66]

went out front of my house and did a 1 hour exposure of the stars. i put my lens in a ziplock bag and left it outside in the cold for a half hour, then i took the camera out of the bag and took the shot, came back and hour later to release the shutter and the lens was fogged up. how do i keep it from fogging on long exposures (40 degrees outside)

That's almost the opposite of what you want to do.

Set it up outside. No special precautions (except for maybe taking the battery out if it's really cold).

Let it equalize with the ambient air temperature, then you will be fog free.

Put it in the bag before going back inside.