bill@hpfcla.UUCP (02/18/86)
Along the same lines as the basenote asking about cold weather camera operation: What about lenses? I've read that if I take a lense out in the cold, I need to put it in a plastic baggie before bringing it back into the warm house. Is this true? How cold is "cold"? Any tips would be appreciated, 'cause winter offers some of the prettiest shots, and I'm too paranoid about ruining my lenses to risk shooting them! Bill Gates ihnp4!hpfcla!bill-g
hofbauer@utcsri.UUCP (John Hofbauer) (02/26/86)
> What about lenses? I've read that if I take a lense out in the cold, > I need to put it in a plastic baggie before bringing it back into the > warm house. Is this true? How cold is "cold"? Any tips would be Both cameras and lenses are high precision instruments which are more sensitive to corrosion than a hammer or screwdriver, lets say. When you bring something into a warm environment from a cold one water will condense on it. Recall what happens to your eyeglasses. The water will cause corrosion and your equipment may stop functioning. By placing it in a plastic bag and evacuating as much air as possible will prevent the warm room air from coming into direct contact will the cold surfaces and so the condensation will occur on the outside of the bag. After a few hours the equipment will have warmed to room temperature and you remove it from the bag. Don't forget to seal the bag tightly. The kind of problems that might arise are rusting of the diaphragm blades and water droplets forming between the lense elements. All lead to expensive repairs or junking the equipment.
greg@utcsri.UUCP (Gregory Smith) (02/27/86)
[Not to be taken away] In article <2208@utcsri.UUCP> hofbauer@utcsri.UUCP (John Hofbauer) writes: >> What about lenses? I've read that if I take a lense out in the cold, >> I need to put it in a plastic baggie before bringing it back into the >> warm house. Is this true? How cold is "cold"? Any tips would be >When you bring something into a warm environment from a cold one >water will condense on it. Recall what happens to your eyeglasses. >By placing it in a plastic bag and evacuating as much air as >possible will prevent the warm room air from coming into direct >contact will the cold surfaces and so the condensation will occur >on the outside of the bag. After a few hours the equipment will Mostly true. When you bring a cold object in, water condenses on it. This is because inside air has a higher _absolute_ humidity level than outside air, and the object's temperature is below the dew point for the inside air but not for the outside air. Sealing a lens in a baggie _before_ you bring it in seals all that nice dry air in, preventing condensation. Note that the _relative_ humidity is usually lower on the inside in the winter, because heating air increases its capacity to contain moisture, thus lowering the relative humidity even if the same amount of moisture is maintained ( Relative humidity is (amount of moisture)/(max moisture) %, where (max moisture) is the most moisture that can be carried without condensation. This increases with temperature ). Greg Smith University of Toronto