Understanding Binocular Power- The Magnification Power
Power!. We are not talking about the power supplied by your local electricity company. We are referring to binoculars magnification power. Why is understanding binocular power important? Well, we will get to know why soon.
In binoculars, power always refers to the magnification power of the binoculars. the primary purpose of binoculars as you may already know is for magnification. binoculars are basically made of lenses and prisms to help enlarge whatever you are seeing. for more explanation, check out how binoculars work.
In almost every area of life, binoculars are used in one way or the other. But they are mostly loved by the outdoor enthusiasts and the military. Those who like hunting, hiking, bird watching, boating/marine, traveling, astronomy, etc. see some of the common uses of binoculars in my recent article.
What is Magnification Power?
Since the primary use of binoculars is to magnify whatever that we are looking at, so the magnification power is the most important specification on the binoculars. Magnification power is often given as the first number in a binocular description (e.g. 7x35, 8x50), magnification is the ratio of the focal length of the objective divided by the focal length of the eyepiece.
The magnification from the example above is 7 times. In other words, you can view images up to seven times larger than what they appear to the naked eye.
As you can tell from the definition of the magnification, it is how many times the binoculars can make the object you are viewing appear bigger than your normal eyes would see. The magnifying power number is usually visible in every pair of binoculars.
The first number is always the magnification always indicated as “7x”. the second number following the magnification is as equally important which is the objective lens diameter size “35mm” and its always measured in millimeters. The objective lens size determines the light gathering power of the binoculars and how powerful it is.
Binoculars magnification comes in different numbers. It is not necessarily true that the larger the binoculars’ magnification is, the better they are. On the contrary, higher magnification can result in blur and unclear images if you are moving or your hand is shaking. Binoculars with high magnifying power are very sensitive to movements including handshakes.
Any movements you make, those also get amplified by the binoculars thereby, producing unclear and unsteady images. A larger magnification leads to a smaller field of view and may require a tripod for image stability.
The 5 most common magnifications in binoculars are 5x, 7x, 8x, 10x and 12x. In other words, you can magnify the image up to five times its actual size as seen through the naked or unassisted eye, up to seven times, eight times, ten times or twelve times.
However, in recent year, this problem is been solved in civilian binoculars as well by applying a technology called image stabilization(IS) which previously was used in the military only. This technology when found in binoculars which have high power, auto corrects the image blurriness. This allows the user to see clear and bright images even with high power binoculars.
Lets elaborate more on the second number which is the objective lens size.
Understanding Objective Lens Diameter Size
The objective lens size also determines how farther you can see and the quality of the image you will be viewing. The bigger the objective lens size, the heavier or bulkier the binoculars will be in your hands. But the more powerful they will be as they can gather more lights from the object inside them at once.
These lenses are coated to reduce internal reflections. As it is known, as lights travel from one medium to another especial from air to lens/glass. some of the light rays are absorbed while some gets reflected. Which might cause blurriness in image production. that is the reason why you will find that lenses used in binoculars are often coated with chemicals to reduce this reflection in order to produce bright and clear images.
These are the kind of objective lens coatings you will find in the market. the more coating layers that are applied to the lens the more powerful it is and the better images the produce. Here are the coatings types.
- Coated: one or more surfaces coated with a single layer.
- Fully coated: all air-to-glass surfaces are coated with a single layer.
- Multi-coated: one or more surfaces coated with multiple layers.
- Fully multi-coated: all air-to-glass surfaces are coated with multiple layers.
The objective lens size goes hand in hand with the magnification. most often you will hear terms like compact, full-sized, etc. The objective lens size is often used to classify binoculars.
Below are the four typical sizes of binoculars;
- Compact with lenses between 25mm – 28mm in diameter,
- Mid-sized with lenses at around 30mm in diameter,
- Full sized with lenses in the 40mm – 42mm range,
- Larger sized with lenses 50mm in diameter and above.
Let’s look at some of the uses of binoculars and the optimal magnification power.
Quick Chart for Choosing the Optimal Binoculars Power
For every Any Waterproof Model with A Large Objective Diameter and Rubber Armoring, 7×50(standard binoculars for mariners), 7×42, 8×42 & 10×42.
All binoculars that are Rubber Armored, Waterproof and Fogproof Models,7x to 10x Power Models for General Hunting,12x or 16x for Distant Game/Varmints, Compacts fit in a Pocket for Hunters on the Move and are ideal for daytime hunting.
For outdoor activities, Any 7×35, 7×50, 8×42 & 10×42 Standard Size, 8×30 & 10×30 Compacts, Waterproof Models for activities like Camping hiking, etc will be perfect.
for bird watching,8×42 is the standard or optimal, 10×42, 10×50 & 12×50 for Details in Smaller Species at a Distance, Compacts with a 30mm or Greater Objective Lens size, Any Binoculars with Long Eye Relief and have Good Close Focusing Ability are great for.
Equine Sports and Stadium Sports
The Compact sports: 4×21, 8×25 & 10×25 Xtra-Wide Angle are optimal. Mid-Size: All 7×35, 10×50 &12×50, Any Zoom, Compacts from 7x to 10x.
For low light conditions 7×50 (Best Light-Gathering), 8×42, 10×50.
Indoor concerts 5×25 & 8×25 Xtra-Wide Angle, 4×30, 7×18 & 7×21
for Compact models, Any Zoom or Wide Angle Model in this range is good.
7×35, 8×42, 10×42 & 10×50, Most Compact and Wide Angle Models.
Understanding Binocular Power is an important element in choosing the right binoculars for what you are looking to use them for. The magnifying power of the binos will enlarge whatever you are looking at for a perfect view. So it is important to select the right magnification.
Josephine is Content Manager @ Binocularsinght.com, an Electrical Engineering Grad who loves optics. She is an Outdoor Enthusiast and a Writer who likes escaping into the mountains for hiking adventures and enjoys other outdoor activities as well.