You’re in a forest in springtime, you’ve got your binoculars, you hear a bird, you swerve your binoculars to where the sound is coming from and realize that you can’t see a damn thing. That’d suck, right?
When you want to see something, say… the moons of Jupiter or some rare bird, but the eyes the good Lord gave you just won’t do the trick, you may need a pair of binoculars. Ahh yes…From military espionage to bird watching, binoculars have been around to give us a view of a bigger world. So here are some basic things to know about binoculars. Hopefully, they might help in choosing the best binoculars for you.
First on the list is magnification. Yes, that’s right. It’s when something looks bigger how it initially looks like. Magnification is the main purpose of binoculars. Technically, it’s the projection or appearance of images in the way of how it would appear if you were closer to the image without having to, well, move closer. To magnify objects, lenses are used. Lenses are transparent objects, usually glass, that are shaped in such a way that they refract light to produce a real or virtual image.
The difference in magnification is correlated to the purpose of the binoculars. For example, bird watching binoculars have about 7 to 12 diameters magnification. This means that looking through binoculars with this configuration would look as if you were looking at it as if you were 7-12 times closer to it. Military binoculars and those used by amateur astronomers have greater magnifying abilities. This is related to the field of view, which is just the amount of space you could see. The more magnified a view is, the smaller the field of view.
The next thing that comes in handy to know about is the exit pupil. This is a beam that determines how much light is gathered and how bright an image is. To get the brightest images, the exit pupil should be the width of a fully dilated iris of a normal human eye, about 7 mm. When choosing how large the exit pupil should be, you should consider the conditions where you will use the binoculars and how your iris would react in such conditions. If youo do it in the daytime, your pupil would be dilated at about 3 mm so using binoculars set to 7 mm would just be a waste of light.
The last thing would be about eye relief. Eye relief is the distance the observer must position his eyes on the eyepiece to see a clear image. Choosing binoculars with a longer eye relief would mean choosing one with a longer focal length. This would really benefit people who wear glasses because they would inevitably need to put the binoculars farther from their eyes than usual.
