Is my bushnell insta vision 7x35 or 10x50- how do I tell ?
The first number is the magnification the second number is the size in millimeters of the objective (large lens) So if you measure the diameter of the front large lens that will give you the size. So a 10x50 means a magnifyng power of 10 and an objective of 50mm.
Now to find out the magnification if you don't know what it is. Measure the front lens. Then if you look through the eyepiece lens while holding it away from you you will see that there is in each a small circle of light. That it what is known as the exit pupil. It lines up with the pupil of your eyes when you have the binoculars pressed up against your eyes. Now measure the diameter of the exit pupil in millimeters. It will only be a small number.
To work out the magnification use this formula. Magnification = Objective size divided by the exit pupil.
So a 10x50 will look like this M = 50 divided by 5....therefore M =10 which is the magnification.
Both the 7x35 and 10x50 will have an exit pupil of 5mm. So if yours is one of these then all you need is the objective (large) lens size.
Aug 04, 2009 |
Bushnell InstaVision Binocular Binocular