Avoiding Fogged Lenses

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Today’s Question: I am the photographer for a local volunteer fire department. I usually keep my camera bag in my truck year-round as I felt it was better to keep the camera at the temperature it would be working in rather than a warm (cool) house then quickly to a cold (hot) outdoor temperature. I haven’t had any real condensation issues, but I am not certain that some may have occurred which will haunt me later. What is your advice for people who need this ready access to extreme temperature changes?

Tim’s Quick Answer: Keeping the camera in a warmer environment close to the ambient working conditions can help prevent fogging up of the lens caused by taking a relatively cold lens into a relatively warm and humid environment. However, if this means storing the camera in a humid environment, I would suggest taking measures to avoid having the camera exposed to relatively high humidity for extended periods of time.

More Detail: In terms of the immediate issue of capturing photos, taking a camera from a relatively cool environment to a hot and humid environment can cause the lens to fog. Merely wiping the lens with a lens cloth will only provide a temporary solution, as the lens will then continue to fog up until it has warmed up to closer to the ambient air temperature.

For example, when I am teaching onboard a cruise ship in a tropical environment such as the Caribbean, my camera is kept in an air-conditioned room. If I see something that warrants capturing photos, I can grab my camera and head outside. However, because the lens will be relatively cold at that point, the front element will immediately fog up. If I wait about five minutes, the lens will warm up closer to the ambient air temperature, and the fogging goes away with no additional intervention required.

In this type of situation, you can avoid the fogging by keeping the camera stored somewhere where it will remain at about the ambient temperature. That could be an area of a vehicle, provided the camera won’t be exposed to extreme heat in this case. If the camera is already at about the ambient temperature, you would not see condensation as you do when taking a cool camera into a warm and humid environment.

However, there may be some concern of relatively long-term exposure to humidity, which have the potential to create problems for the camera. Therefore, I would suggest taking steps to keep the camera dry while at the same time keeping the camera at about the ambient temperature. For example, you could put the camera in a plastic bag that can be sealed, and include a desiccant in the bag with the camera. This will help ensure the humidity is relatively low in the bag, helping to keep the camera in conditions that are well within the operating limits recommended by the manufacturer.