Range Binoculars?

Binocular are rated with two numbers, such as 7x30. The first number is the magnification, and the second is the light gathering power. That means that things are 7 times bigger (and therefore 7 times online medicine without prescription dimmer). The second number means that the first lens is 30 mm wide, which is about 10 times more than the human eye. This more than makes up for the dimming caused by being 7 times magnified.

Your 10x30x50 binoculars are really zoom binoculars, with a magnification of 10 to 30 times. The "50" is 50 mm, the size of the first lens.