Introduction

How do I calculate Twilight Factor?

How do I calculate Twilight Factor?

Twilight factor is the number used to calculate the relative effectiveness of binoculars in low light situations, such as hunting at dusk. You can calculate the twilight factor by taking the square root of the total magnification and multiplying it by the objective lens diameter. For example, the twilight factor of an 8×42 binocular is 18.3.