Optical Issues for Hunters

By Glen Wunderlich

The end of regular firearms deer season signals a more normalized routine for deer that had become almost invisible to the throng of orange. It’s almost incomprehensible how even an abundant population present in much of Michigan’s southern zone seems to vanish totally when all those crunching boots march into their habitat. We wonder: Where did they go?

Obviously, some have been stowed into freezers and canning jars; the most fortunate of the herd receives a crash-course in survival and dwells in cover so thick the average hunter dares negotiate. However, in the two weeks that have passed, deer sightings in the open have increased.

What is different, though, is how little shooting time is left in a given day when deer become active. Prime time is concentrated into about 30 minutes of waning daylight that presents a challenge to the human eye: available light.

Without good optics a hunter is at the mercy of his naked eyes. Younger hunters, however, have the advantage of eye muscles that allow the eyes’ pupils to be held open at a larger diameter than older folks. In fact, by age 60 a person’s eyes have lost over 40 percent of their ability to access available light; by age 70, the decrease is over 50 percent, as explained in Modern Hunting Optics by John Barsness.

Binoculars and firearms scopes also have “pupils” referred to as exit pupils. And, here’s where the older generation can regain the advantage of youth. The larger the exit pupil of an optic is, the more light it can produce to the eye. Applying a simple formula, based on a given optic, indicates the level of light being presented by dividing the size of the objective lens (the forward lens of an optic) by the magnification. For example, my compact Leupold Katmai binoculars are 8 power with 32mm objective lenses, giving an exit pupil value of 4. Yet, the scope on my muzzleloading rifle is a variable power from 2.5 to 10 power with a large objective lens of 50mm.

Even at full-power magnification, the scope’s exit pupil is larger than the binoculars The science of mathematics was revealed to me, as I glassed a number of deer in the last 10 minutes of legal shooting time on an overcast afternoon stand a few days ago. I had learned first-hand the disadvantage of compact binoculars. Sure they are convenient to carry, but when deer activity begins to pick up in the twilight, the smaller lenses can put a hunter out of business before the final bell tolls.

There’s more to the equation than the size of the glass and it comes in the form of quality and coatings. And, this all comes in the form of cash, although the amount required is far less today than it was some 25 years ago, because of advancements in technology.

You won’t see a difference peering through scopes in the bright lights of any retail outlet, but the advantage of superior optics becomes clear as day when light is fading to nothingness. In summation, when you are shopping for optics, understand that better glass will pay dividends in the form of prime time afield.   It’s your choice to be thoroughly involved when the action picks up or to pack up.