Of the thousands of people we speak with each year at shows, on the phone or by email, virtually all gravitate to the 10x binocular because it just has to be better due to its higher magnification. People ask, “Won’t I see more detail with a binocular that brings objects 10 times closer vs 8 times closer?” Well, let’s take a look at the facts.
When looking through a binocular, everyone will experience a certain amount of shakiness to the image. Trying to hold a binocular steady while studying a whitetail at 200 yards is not an easy thing to do. Unless you don’t have a pulse, you’ll be faced with the challenge of remaining still enough to truly study detail. Guess what? Ten power binoculars not only magnify the image by 10 times, but also magnify the shake in your hands by 10 times.
At events, I’ll tack a dollar bill on the wall about 20 feet away and ask the person/group to read the serial number. To prove the point of how much we shake, I’ll let them start with a 12x binocular. Figuring it will be easy, they quickly realize it’s almost impossible. Then, I’ll hand them an 8x and ask them to read it. At 8x, it’s still a difficult task, but not like the roller coaster ride of trying to study the detail at 12x.
It’s important to understand that just because the image is bigger doesn’t mean you can verify detail. So the truth is, if you can’t hold a 10x binocular steady, you will actually get better results in the field with an 8x. The advantages of a larger image are sometime not practical because your every movement is also magnified.
Field of View
Why would I be able to see more with an 8x and not a 10x? Let’s compare the TORIC Flagship 10x42 vs. the 8x42. Both have the same Ultra High Definition optical system, magnesium alloy body and virtually the same height and weight. The reason is something called Field of View (FOV), which is measured in feet at 1,000 yards. All things being equal, a lower powered binocular will provide a larger field of view. Check out the chart below and you’ll see that our TORIC 8x actually gives you a 10 percent wider area than the 10x (377ft vs 341ft).
Let’s use a practical hunting application to better explain. Generally speaking, a wider field of view makes it easier to spot a whitetail trying to slip through a heavily wooded or thick brush because you can scan a bigger area to see movement. In the photo below, the magnification is greater on the right, with a 10x binocular. But all you can see is a small portion of the deer. Notice in the picture on the left how the wider FOV allows you to see the animal much easier. All you need to locate a whitetail is catch a subtle movement in the brush like the flicker of a tail or ear. If you’re hunting east of the Mississippi River, it's easier to locate a deer with a lower-power binocular.
According to the Vision Council of America, 64 percent of Americans wear eye glasses. And have you ever noticed how they tend to prevent you from seeing the full image through a binocular? Eye relief is what let’s those of us who do wear glasses use a binocular unhindered.
Really, you'll want to pay special attention to the eye relief specification on any binocular, especially when considering a 10x. For eyeglass wearers, 16mm of eye relief is the absolute minimum. It’s optimal to get a binocular with 17mm to 19mm so you can see the entire FOV the binocular was designed to allow. In the TORIC Binocular Specs chart above, you’ll notice that the TORIC 8x42 provides an incredible 19mm of eye relief vs the 17mm on the 10x, which comparatively speaking is excellent for a 10x.
Light Gathering Ability
The incredible design of our eye pupils allows for us to gather or reject light based on the lighting conditions of our surroundings. Your pupils will open to 5-7mm when the light starts to diminish, hence the reason you can see in the near dark. On the contrary, your pupils will shrink to almost 2mm during bright light conditions to protect your cornea. However, binoculars are not built that way. The light gathering ability of a binocular does not change, so it’s important when choosing between 8x versus 10x binoculars that you know the facts. The amount of light can vary greatly throughout the day and into the night. The size of your entrance pupil can change in size from as little as 2mm to over 7mm in diameter.
At the key hunting times of dawn and dusk, your entrance pupils are around 4-5mm in diameter. Since most of us hunt in low light, you’ll need a binocular that meets or exceeds the size of your entrance pupil during the time you plan to use it. The TORIC 8x will give you 5.25mm of light vs. 4.2mm from the 10x.
We know this by measuring the size of the binoculars exit pupil. The exit pupil is the actual image in the eyepiece as it leaves the binocular to enter your eye. A more technical definition of exit pupil is the diameter of the shaft of light (expressed in millimeters) that exits a binocular’s eyepiece that can enter through your eye’s entrance pupil. Exit pupil is calculated by dividing a binocular’s objective size by its magnification. For example, 42mm/8x = 5.25mm or 42mm/10x = 4.2mm.
Under bright light, your pupil may constrict down to 2mm, causing some of the light that emanates from a 5.25mm exit pupil to go unused because it’s blocked by the iris (above left in diagram). However, under dawn and dusk conditions, your pupil will dilate up to 5mm or more (above right). Thus, an 8x42 binocular will deliver the maximum amount of light that your pupillary opening will accept.
Facts are facts. For these conditions and uses, I’d save the $10 and buy the best 8x42 binocular the hunting community has ever seen: the TORIC 8x42 with 377 foot FOV, 19mm of eye relief and 5.25mm exit pupil. Enjoy my friends.