In cold or humid weather the Anti-Fog Eyepiece Ed accessory attaches easily to reduce condensation and help you maintain a clear view of your subject.
When warm air touches cold glass, moisture in the air is condensed. Camera and binocular finders are no exception. In photographing at a cold place of ski or skate, the breathing of a cameraman or moisture transpired from his/her eyes dims the finder.
For this reason, you cannot concentrate your attention on photographing or miss a decisive moment, and it was a troublesome problem for professional cameramen who are required to perform accurate photographing all the time. The anti-fogging eyepiece was developed to solve such problems. Subsequently, eyepieces for binoculars were also marketed and are demonstrating their effectiveness for bird watching, astronomical observation and other activities.
As the conventional anti-fogging technique, methods of drying with a hot-wire heater and of coating with a surface active agent such as wax are available. But these methods cannot be used for optical products because of such problems as surface accuracy and durability. The anti-fogging technology developed by Canon is to absorb moisture with a thin membrane of moisture absorbing polymer formed on the glass surface. Since it maintains a stable state with almost no physical change, it is optimum for application to optical products. Although the amount of absorbed moisture is limited, moisture naturally evaporates. Through repeated moisture absorbing and transpiring, it maintains the anti-fogging effect for a long time.