Why High Humidity is bad for your equipment
High levels of humidity can damage your lenses and certain parts of your camera body. Fungus grows in between lens elements and under the lens coatings. Once fungus gets started, it causes blurring parts of your photographs.
If you like to store your equipment in camera bags, dark cupboards, or basements then you are in for trouble. Fungus or Mould like dark, humid places where there is little, or no movement of air. Keeping your camera in storage for too long is inviting disaster. Lenses and cameras need to be kept in use and exposed to light and fresh air from time to time. If you store camera or lens wisely and use them correctly they are likely to give you years of trouble free life.
Optimal storage for lenses and camera equipment are at a relative humidity (RH) of around 35% to 45%. A good rule of thumb to figure the optimal RH to store your equipment at, is to look at it’s optimal operating humidity range, and half it. For example, the Canon EOS 5D’s operating humidity range is 85% RH or lower, so a good indicative range to store it would be between 35 and 45% RH.
Why Low Humidity is bad for your equipment
Remember, that you could also run into problems from keeping your relative humidity levels too low. All camera lenses and bodies have a number of moving parts which re all lubricated with a light machine oil. Keeping your RH too low could dry up that oil quicker than usual, making these parts wear out sooner, and work sluggishly. Rubber on the camera also tends to harden quicker in dry air.
So what’s the solution?
Sunlight / UV Radiation
Put your camera out in the sun from time to time. Remove the lens (or you could end up with a hole burnt in your shutter or some other part), filter, body, etc, and put them all out in sunlight for a while. If you manage to work this into your monthly camera care routine, you should be fine.
You could also try what some photographers do: use a UV lamp in their storage area. Why? Because prolonged exposure to UV (Ultra-Violet) radiation kills or retards fungal growth. Do remember to take your UV filters off if you decide to try this method out, because they are designed to keep UV rays out of your lenses. The lens coating blocks UV light too, to an extent.
What if you live in a region that is perpetually humid like where I stay (coastal belt of India)?
Silica-Gel is the cheap way out. It is a dessicant (something that de-humidifies the air in the vicinity of your camera equipment).
You can buy Silica Gel either as crystals, or sometimes as tiny spheres. Most often you find them in porous sachets so that they don’t disperse among your equipment. If you decide to go with Silica Gel for your cabinet, remember that you should get the indicative variety. They are blue when they’re fully absorbent, white-ish when they’re partially full of moisture, and pink when they’re fully saturated. You can “Re-charge” your Silica Gel at this point by drying the silica in a oven or under the heat of sunlight
You’ll need a container like the Dry Storage Silica Gel Dehumidifier to store it, yet create enough air-flow through the crystals. You’ll also generally need lots of silica gel. But remember that it lasts a long time, and needs no further investment. Remember, that keeping saturated silica-gel in your camera storage could do you more harm than good by actually releasing more moisture into your storage.
As with everything, there has always got to be an expensive option. De-Humidifiers usually use mechanical means to reduce the relative humidity of the air around it. De-Humidifiers are usually quite effective, and can reduce the time you spend on modifying your camera’s environment, but they generally draw significant amounts of electricity. You could also use your Air Conditioner to reduce the ambient humidity to a safe level for your camera equipment. This is because Air Conditioners dehumidify as they chill the air, leaving a comfortable storage humidity for lenses and cameras.
To wrap up, remember that the best maintenance/fungus prevention plan for your camera involves your regular use of the equipment. Regular use keeps the lenses and camera body aerated and exposed to sunlight, thus killing fungus.
If you don’t use your camera often, make sure that it is stored in a well ventilated area with an ambient humidity range of 35%-45% RH. Also remember to take it out often and expose it to sunlight.
If you live in a humid part of the world, you could try either Chemical Desiccants or De-Humidifiers.