Hunting Optics

Tip : Binoculars are great hunting tools. Basic binocular savvy means knowing what the numbers mean in terms of hunting performance.

With binocular designations such as 7x35, 8x24, 10x42, etc., the first number is magnification power. A 7x glass magnifies a distant object seven times; a 10x, 10 times and so on. The second number is the diameter of the objective lens in millimeters. Together with power, the objective diameter determines how the binoculars perform in low light.

Dividing magnification power into the objective size gives the exit pupil diameter. This determines how much light gets to the eye, which has a maximum pupil diameter of 6mm. A 7x35 has an exit pupil of 5. An 8x24 has an exit pupil of 3. An 8x42 has an exit pupil of 6.

High-power 10x binoculars give large images at some cost of low-light performance. Medium power ranges (7x35 or 8x42) provide the most light-transmitting efficiency. Compact binoculars, such as 8x24, offer easy carrying convenience but transmit less light.