National Geographic Binoculars Owner's Manual - page 5
Optical Magnification
Linear and Area Magnification Compared
The view on the left is the view as seen by the unaided eye. The view on the right is as seen
through a binocular with 5X linear magnification. The kite in the right hand image measures 5
times wider than in the original view.
Now, if we take the circular area of the right hand image and draw it in the left hand image we
see that it fits in approximately 15 times. Likewise, the small circle that shows the kite in the
left hand image will fit into the right hand image 15 times. This shows that the magnified image
on the right has an area magnification of about 15X.
So the relationship between Linear magnification to Area magnification is about 3 times.
A binocular with 12X linear magnification yields about 36X area magnification, while a 36X
linear magnification binocular shows about 108X area magnification.
Care of your binoculars:
1)
Always treat your National Geographic binoculars with care.
2)
If waterproof binoculars are exposed to saltwater spray, rinse them in clean fresh water before
drying them with a clean, soft cotton cloth.
3)
If any of the lens surfaces need cleaning, breathe on the lens and gently wipe with the cleaning
cloth included with your binoculars. If extensive cleaning is needed, use camera lens cleaning
tissues and lens cleaning fluid. Never use cleaning cloths or liquids designed for eyeglass lenses.
They may damage the coatings on your binocular lenses.
4)
Always store your binoculars in their protective case or pouch.
5)
Protect the lenses by using the lens caps when not in use.
6)
Keep your binoculars secure by using the supplied neck straps or cords whenever possible.
7) Shock-resistant binoculars are carefully constructed to withstand rough treatment, however,
this does not mean that they should be intentionally abused.