[AlanM]

This is more of an academic question as it does not seem to be an issue in real life. However, consider this: Camera and lens is assembled indoor at room temperature. The camera is brought outside in the cold. The camera cools down. Now, what happens to the water vapour trapped inside the camera? I guess it doesn't condense/freeze on the sensor or elsewhere in the optical path. But what happens then?

[stevebrot]

I guess it doesn't condense/freeze on the sensor or elsewhere in the optical path.

Ummmmm...yes, it does. Trapped moisture and transition from warm to cold can be a huge issue. Body and lens seals work against us under those conditions.


Steve

[AlanM]

That's what I would have thought as well. Yet, you see photos of snowy landscapes. How is that accomplished? Keeping the camera warm in some kind of "heated" bag? What would be the best way to avoid condensation/freezing if going on a long hike in winter?

[othar]

As stevebrot said, yes it does.
The reason this is rarely an issue is, that it is usually a dry heat inside your home, so there is not much water to condense to begin with. I would advise against changing lenses in the kitchen (when cooking) or a greenhouse though.

[Fogel70]

If you keep the gear in an closed isolated bag for a while when going from warm/cold or cold/warm, then the gear will cool down or heat up slowly avoiding issues with condensation.

[MarkJerling]

Basically, you're dealing with the dew point of air and this is dependent on the moisture content of the air and the temperature. When taking a cold camera from a cold area to a warm one will not always cause visible condensation to form as warm air has a higher capacity to hold moisture than cold air. Note, I say "usually". There are exceptions to this: When, for instance, taking your camera into a warm greenhouse, when the indoor area has a very high humidity. Then, condensation will form on the (relatively speaking) colder camera. Likewise, when taking the warm camera outside, condensation seldom forms on the camera as the capacity for cold air to hold moisture is much lower than for hot air. So, what works best when going to from the one to the other is to ensure that you slowly bring your gear to the same temperature as the ambient air temperature.

[Andrea K]

The worst is cold->warm->cold . Some photographers, when they work in very cold countries, tend to leave their gear outside to avoid the "warm->cold" part.

[AlanM]

Thanks to all of you for your explanations. However, if I look at the maths and physics, things should start getting messy around 5-10 °C. If you look at the vapour pressure of water (Vapour pressure of water - Wikipedia) at 20 °C and assume a relative humidity of 50 %, then the dew point will be reached at 10 °C. If the relative humidity is really low (30 %), the dew point is reached just above the freezing point. So could it be that other parts of the camera than the sensor and back element of the lens cools down faster causing condensation to occur there?

[othar]

Thanks to all of you for your explanations. However, if I look at the maths and physics, things should start getting messy around 5-10 °C. If you look at the vapour pressure of water (Vapour pressure of water - Wikipedia) at 20 °C and assume a relative humidity of 50 %, then the dew point will be reached at 10 °C. If the relative humidity is really low (30 %), the dew point is reached just above the freezing point. So could it be that other parts of the camera than the sensor and back element of the lens cools down faster causing condensation to occur there?

You have to take into consideration the relatively small amount of air inside the camera, so even when it starts to condense you don't immediatly get a problem (the damping material inside the mirror box and similar materials inside will temporarily absorb some of the water too)

[Fogel70]

You have to take into consideration the relatively small amount of air inside the camera, so even when it starts to condense you don't immediatly get a problem (the damping material inside the mirror box and similar materials inside will temporarily absorb some of the water too)

And it takes time for the camera to cool down, so when the inside of the camera case has reach the lower temperature, the air inside the camer has also been cooled down.

So it is not as big problem as when hotter air meat the cooler outside of the camera if bringing in a camera from the cold.

[DonV]

That's what I would have thought as well. Yet, you see photos of snowy landscapes. How is that accomplished? Keeping the camera warm in some kind of "heated" bag? What would be the best way to avoid condensation/freezing if going on a long hike in winter?

Be sure your camera gear is "dry" where it is stored. Various "drier" products are available for this purpose.
Your gear in a controlled environment is you friend, and should be a consideration for routine storage.

How long the hike is really does not matter, any condensation will happen as soon as the gear is chilled; continuing to get colder may cause freezing.

I think you are looking for a problem that you may not find, winter air in your part of the world is pretty dry, I'm guessing the humidity inside is also low.
If your inside air is 30% relative humidity and you go out into zero degrees, the outside humidity is likely even lower and any moisture will "evaporate" or flow to the less moist outside air.
It is much more likely that you will get condensation on the outside of the gear when you return to a warmer, more humid environment.

As pointed out above, a sealed camera may be an exception- so store your gear in a controlled humidity environment, even if it is just inside a bag with a container of silica gel.

[reduno]

I think you are looking for a problem that you may not find, winter air in your part of the world is pretty dry, I'm guessing the humidity inside is also low.
If your inside air is 30% relative humidity and you go out into zero degrees, the outside humidity is likely even lower and any moisture will "evaporate" or flow to the less moist outside air.
It is much more likely that you will get condensation on the outside of the gear when you return to a warmer, more humid environment.

I agree that if you are taking the camera from a relatively low humidity location, the amount of trapped water vapor will be very low and shouldn't be a problem. If you do get any condensation inside the camera, it is going to be on the parts that get cold first. This is likely to be on the inside of the outer covers and not likely to impact camera operation. Storing your equipment in a low humidity environment is beneficial for many reasons, not just the possibility of condensation.

[AlanM]

I did a little calculation. Using the ideal gas equation, temperature 20 deg. C, volume inside camera 0.1 L (guestimate) and relative humidity 50 % gives 0.9 mg water, which is not a lot but it only takes a thin layer of water to mess things up. Anyone knows if the sensor inherently repels water or is treated in such a way as to repel water?

[11GTCS]

As others have mentioned, it can be a issue, but honestly In temperate climates shooting routinely in the winter I’ve never had an issue in the decade or so I’ve been shooting regularly. If you live in a very humid climate, bringing the camera in and out of AC might be worse for it than winter time with dry air on both indoors and outdoors. If you’re very concerned, the suggestion other people have made of putting your gear into a humidity controlled box when not in use can be wise as well.

[DonV]

If you have 50% RH where you are storing your gear, you already need to be doing some "climate" control; if nothing else that RH will allow mold to grow.