Question Lens fogging

[steph]

So the camera lens fogs up when I bring it back inside from the cold . Nothing unusual so far. Normally, if I keep it indoors, it would take 10-20 minutes for the water droplets to evaporate and for it to be clear again. BUT if I take it outside in the cold again, within a minute or two, all the condensation is gone.
I'm having problems understanding why, as inside it's warmer and the moisture should, theoretically, evaporate faster there. One possible motive would be that cold air (4 degrees right now) holds less moisture, so it's "drier" than the air inside and the water droplets can evaporate faster. But I don't know how this fares when confronted with the fact that Relative Humidity is much higher outside (It's actually a foggy atmosphere, so probably close to 100% ). If needed, I can do a video demonstration if the explanation isn't enough.
I've been thinking that maybe it's heat from the camera itself, but it happens even if I keep it on all the time. And it doesn't have a lens heating element.

 

[C3PO]

You get condensation when warm air hits cold objects. The object cools the air raising the relative humidity, and if the air reaches the dew point (100% humidity) Voilà! Condensation.

 

[steph]

Yep, idiot me forgot to realize that, outside, the camera is warmer than the surrounding air and that drives the evaporation and protects it from condensation. Inside the room condensation is still occuring for some time on the camera and it takes a while until it reaches room temp (or higher, if a heating source is used) and the evaporation starts again.

 

[C3PO]

Bingo! :thumbup:

Thinking in "physics mode" about real events takes practise. I've encountered many people that were "good" at math but couldn't use it to solve a real life problem. Just keep questioning things and you will become good at it.