Question about cold weather and lenses

[CharlieMopps]

So, My wife is a semi-prof photographer (does weddings and familly photos)

Anyways, so she has this fancy digital camera and a really expensive low-light telephoto lens. The thing is HUGE.

With the full moon tonight, I figured it would be cool to take pictures of it. But it's really cold out here... any tips? Should we put the camera in the garage for a few hours prior to get it to the same temp as the outside?

[aurora]

One tip would be to leave the lens uncovered when you bring it inside, as it will dew up and you want the dew to evaporate.

[RickJ]

A full moon is actually the worst time to shoot it as it is like taking a photo of a face with the flash right by the lens. You end up with no shadows and a very flat image. I'm sure your wife uses a flash or several off reflectors well to the side to avoid this problem. We do the same with the moon by moving the sun to the side. That is take the photo around half phase. Then you have great shadows and relief, not a flat piece of plaster.

Wide field shots of a full moon rising in which the landscape and moonlit clouds are the real objects of attention do work well but that isn't what that lens is made for.

I'd stop it down a couple stops as well. Usually they are sharper when stopped down a bit. This differs from telescopes which work best "wide open". Stopping down does reduce the light by reducing the aperture which, if the lens were perfect would reduce resolution but such lenses have so many tradeoffs in their designs stopping down one, sometimes two stops usually improves sharpness, especially toward the edges of the frame.

On a driven mount this lens might make a great astrograph. The full moon is like shooting an outside sunlit shot as far as exposure is concerned. So low light is NOT an issue. Slower lenses usually are better for the moon. The fast lens is for faint stuff like star fields.

As to the cold, a telescope working at a much longer focal length certainly needs to cool down. That may be the case with your lens as well. Not having one I've no experience here. My el cheapo lenses didn't seem to need to cool.

Aurora's comment about leaving it uncovered to air dry is right on. Don't try to wipe it or cap it to prevent condensation. Both could lead to expensive disaster. Just let it air dry in a dust free location. The condensation is distilled water so will likely evaporate without a trace. But it could cement on dust already on the lens so give it a camel hair brush dusting before going out.

Cameras go through batteries fast in the cold so be sure you have them fully charged and a set in reserve. Since these are snapshot exposures this won't be as much of a problem as when the shutter is open for several minutes taking starfield shots. Still it is amazing how fast they run down in extreme cold.

You don't say what you consider cold. It was -13F here last night. That's where I consider it getting into extreme cold. A friend of mine who lives in Fairbanks says that's sunbathing weather. My wife lived in Mississippi for a few years and the natives considered +50F extreme cold she tells me. Batteries aren't a problem at that temp but at -13F they are.

Rick