The simple answer is: remove the air. That's one nice thing about the mirrorless cameras, they are small and many can fit into the kinds of zipper lock bags you might have in your kitchen. Ditto for lenses.
It's the air that's holding and producing the moisture as you move between inside and outside where there are extreme temperature and/or humidity differences. Thus, reducing the amount of air in and around the camera or lens helps considerably:
- While indoors, bag the camera or lens.
- Remove as much air from the bag as you can, and then seal the bag.
- Take your bagged gear outside.
- Give the bag some time to adjust to the temperature of the new environment before opening it, pulling out your gear, and using that camera or lens.
Use the same technique when you go indoors, just reverse the words indoors/outdoors.
Some people also add a small silica gel (water absorption) pack to their zipper lock bags. There's no perfect solution for extreme environment changes, but this simple procedure helps a lot. Also, if you have control over your indoor environment, then adjusting your humidity and temperature to be less extreme compared to the outdoors helps, too. One other thing: automobiles can retain humidity or reduce it with air conditioning, too, so treat the inside of an automobile the same way you do the inside of a house.
