Cloudiness or fogging on the inside or outside of the lenses is likely to be caused by condensation.
Although this can indicate a leak in the camera, it’s probably caused by a sudden change in temperature. For example, taking the binoculars from a cool, air-conditioned, car into the hot sun can cause condensation on the glass. This can be worse in humid conditions.
Condensation on the outside of your lenses can be wiped away with a microfiber lens cloth, and any moisture on the inside will gradually vanish as your binoculars acclimatise to the temperature.
If you ever notice condensation or moisture on the inside of your lenses, it’s important to leave them in a warm, dry place for at least twelve hours to ensure the moisture is fully out of the device. If left alone it can built up and lead to fungus and mould building up inside your glasses.
Waterproof or weatherproofed binoculars should not suffer from internal condensation due to the way they’re constructed. If you notice any moisture inside them, it may indicate a leak or other problem and you should contact the manufacturer straight away.
If internal condensation becomes a major or regular problem with your binoculars, contact a qualified repair centre or the manufacturers. Never attempt internal repairs yourself as your equipment contains sensitive optical components that can easily be damaged or misaligned.
Always refer to the manufacturer’s manual for specific details.