Learn about binoculars

Binoculars have become a common sight in daily life, but just because you’ve seen them doesn’t mean you understand them, and some people who love photography are still struggling with how to buy the right binoculars.  Different binoculars serve different purposes, so before you buy the binoculars you want, make sure you know what your purpose is.  It’s also an important thing to learn about binoculars is that it can help you buy the right binoculars or use them better.  

1. Objective lens diameter  

The objective lens is the one opposite the eyepiece.  The size of this lens is crucial because it determines the amount of light entering the binoculars.  So for low-light conditions, if you have an objective lens with a larger diameter, you can get a better image.  The lens size in millimeters comes after x. A ratio of 5 relative to magnification is ideal.  Between 8×25 and 8×40 lenses, the latter creates brighter, better images with a larger diameter.  


2. The magnification  

Magnification is a value that indicates how big an object looks when viewed through binoculars.  For example, when using a pair of 10x binoculars, objects from 100 meters away look the same size as when viewed with the naked eye from 10 meters away.  In general, the higher the magnification, the larger the object appears, but the narrower the field of view becomes.  

3. Visual field/exit pupils  

FoW is the diameter of the area seen through the glasses, expressed in degrees.  The larger the field of view, the larger the area you can see.  Meanwhile, the exit pupil is the image formed on the eyepiece for the pupil to see.  Divide lens diameter by magnification to get the pupil.  The 7mm exit pupil provides maximum light for dilated eyes and is ideal for use in dusk and dark conditions.  

4. Eye relief  

This is the distance from the final surface of the eyepiece lens to the eye, at which the full field of vision can be seen through binoculars without dark angles.  If the distance is long, it’s easier to use binoculars even with glasses.  

5. Lens coating  

When light passes through a lens or prism, it bounces off the surface, reducing the amount of light and making the image appear darker.  The surface of the lens is coated with an anti-reflective lens coating to prevent light loss.  There is a single layer of a single coating, and there is a multi-layer coating composed of multiple layers.  Lenses with multi-layer coatings have higher light transmittance, resulting in a bright, clear field of view.  

6. Prism structure  

There are Paul PORRO and ridge ROOF. Theoretically speaking, the structure of ridge ROOF is relatively complex. If the same lens, the same coating, and the same process are used, Paul’s effect will be better than that of ridge ROOF.  But the advantage of the ridge type telescope is its small appearance, exquisite workmanship, so the general high-grade binoculars are used ridge type.  

7. The coating  

About 5 percent of the light is reflected when it passes from air into a glass or from the glass into the air.  Binoculars usually have 10 to 16 surfaces in contact with air, including the objective lens, prism, and eyepiece of each tube.  If these surfaces are left untreated, about 50 percent of the incoming light is lost to reflection.  To reduce this harmful reflection, modern refractive telescopes are coated with a single or multi-layer antireflection film on each optical surface.  


The multilayer antireflective film is made of magnesium fluoride.  The single-layer antireflection film has the best anti-reflection effect only for one specific wavelength of light, and the effect is slightly worse for other wavelengths. It can reduce the reflection of light from each surface to 1.5%, and the transmittance of light can exceed 80% if used on all surfaces of binoculars.  Good multilayers have a reflectivity of only about 0.25% per surface light, such as for all surfaces used in binoculars, light transmittance can reach 90 to 95%.  

8. Color fidelity  

The more natural the color fidelity of binoculars is, the better. High-quality binoculars should faithfully reflect the original color and color saturation of the scene.  To increase the brightness of the telescope, some manufacturers deliberately increase or decrease certain light waves, resulting in distortion and making the scene bluer or redder.  Transmittance and coating are closely related, and directly affect the color fidelity.  All-optical glass with high transmittance and full-surface multi-layer coating, high brightness, accurate color reduction. 

 The general manufacturer won’t announce all data completely, the transmittance of some manufacturers’ chamber of commerce announces local optical glass or coating film, misdirect consumers with this.  

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