The Best Performing Low-Light Binocular
Hunters know that a lot of big game animals move at dusk and dawn, which is why we set out to create a great low light binocular that hunters can rely on. We spend many hours during fall and winter waiting for a big buck to show itself. When the moment arrives, we don’t want to let it pass us by due to poor-performing optics.
Had I understood the benefits of using the right binocular back when I first started hunting, I might have another trophy or two hanging on my wall and more meat in the freezer. I am sure every hunter has had the experience of desperately trying to determine if a deer is a shooter or not in low-light conditions. Heck, in the area where I grew up hunting, we were happy to see a legal buck. I can recall many times when I had to hold off because I was not sure. Better safe than sorry!
Of course, optics are a lot better today than they were 35 years ago. While back then I was more concerned with keeping things lightweight and compact, the little 8x25 binocular I used wouldn’t cut it. Compact binoculars certainly have their place, but they weren't designed for extreme conditions or with a lot of the features that make low light binoculars so valuable.
Light Transmission and Optical Quality
What allows one binocular to perform better over another in low light? It’s not just one element. Rather, it’s a combination of things.
We use the highest quality optical glass available. However, if it’s not coated with enough layers of anti-reflective compounds, a portion of the light will reflect off the glass, reducing the light transmission (as seen in the illustration below). By using the most advanced technologies in the coating process, and applying multiple layers of magnesium fluoride compounds to every air-to-glass lens surface, TRACT binoculars provide incredible light transmission so you can see everything at dusk and dawn.
The addition of extra-low dispersion (ED) glass, which minimizes color fringing to provide extremely sharp edges of contrasting colors, and phase correction and dielectric coatings on the prisms, takes the performance to a completely different level. All of these elements together create what we call the ULTRA HD optical system.
In our initial rollout, all TRACT binoculars have a 42mm objective. The lower the magnification, which in our case is 8x, means the larger the exit pupil. That, in turn, results in a larger light path to your eye. Think of the exit pupil as a window - the larger the window, the more light allowed to come in.
This has no bearing on the quality of the optics, but it is very important because the exit pupil needs to match or exceed the dilation of your eye’s pupil. Since your pupil dilates based upon the amount of available light, (two millimeters in bright sunlight compared to seven in darkness) the binocular needs to provide an exit pupil of at least four to five millimeters to work well, as your pupils will dilate that much in low light. If your eye’s pupil is larger than the exit pupil of the binocular, it will be like looking through a pinhole. When the exit pupil of the binocular equals or exceeds the size of your pupil, it’s like looking through a picture window.
The way you figure out the exit pupil of the binocular is by dividing the objective size by the magnification. For example: 42/8 = 5.25 millimeters and 42/10 = 4.2 millimeters. As you can see, the 8x binocular has a larger exit pupil than the 10x, giving it a larger window of light.
Many people prefer compact binoculars and they have their place, but they don’t cut the mustard when it comes to performing at dawn and dusk. Others like larger objective binoculars, say 50 millimeters, striving to get even more light. But if you do the math correctly, you’ll see that the exit pupil is five millimeters. Is it worth the additional bulk and weight?
As with all optics, there are always tradeoffs. If maximum low-light performance is important to you, choose an 8x binocular. If seeing detail in expansive areas out west is needed, then choose the higher magnification 10x binocular. Either way, TRACT binoculars will provide some of the best extreme low-light performance of any binocular in its class and provide a lifetime of enhanced use in the field.