Mogul wrote:
The better binoculars are filled with nitrogen or argon gas to prevent fogging. I would guess that camera lenses are not because the focusing system would create expansion and contraction. Binoculars can have the focusing mechanisms independent and separate chambers dilled with gas. Some lenses, called duplex lenses because of multi-chamber construction might be amenable to the use of gas, but the space between the chambers would have to be tightly built or perhaps evacuated.
Isn't one advantage of nitrogen that it doesn't expand like air? That was a big promotional point for filling your tires with nitrogen a while back.
Lenses aren't airtight, so the nitrogen wouldn't last long - zoom lenses, anyway.