This is the field of view, the actual angle you see. In this particular binocular, there is a third number, 7.1. That is why astronomy instruments are large, to gather the most light possible. This is usually not very relevant if you only plan to use your binoculars during the day, but if you will be viewing at night then it is very important. The larger the objective the more light can get in the binoculars and the brighter the image will appear. In this case the objective is 50 mm across. The second number refers to the size of the objective in mm. So a 7 x 50 binocular magnifies an image 7 times so that when you look in the eyepiece you see the object as though it were 1/7 of the distance it actually is. The bigger the number the greater the magnification. The first number refers to the amount of magnification. The Objective gathers the image in the form of light while the ocular magnifies the image and sends it to your eyes. An ocular, the small one by your eye, and an objective, the bigger one that you point at the object you want to see. First, What do the Numbers Mean?īinoculars at their most basic are made of 2 lens. I was wondering also why the huge price difference between cheap binoculars and more expensive ones. These pages are a result of my trying to figure all this out. Have you ever wondered what the numbers mean on binoculars, or what makes one binocular better than another, or why one binocular is better than another for a boat but terrible for astronomy.

Binocular numbers