When it comes to binoculars there is a lot to choose from. It is easy to choose wrong because it's really crowded out there. There are many different shapes, sizes and features so where does one start? You will learn about different key features and what they may be good for or perhaps not so good for. Hopefully by the end you know which binocular is right for you.
What do the numbers mean? What are the features for?
Well, say you pick up a binocular and read the numbers 8x40 on it. What does that mean?
The 8 is magnification. This means that objects appear eight times bigger than they are when viewed without the binocular.
The second number, that would be 40 in this case, is the size of the lens on the binocular. That is, the diameter of the objective lenses in millimeters. This determines how much light the binocular lets in and not the field of view. It has nothing to do with the field of view. The bigger the lens, the heavier the binocular. An 8x42 is light but say a 100 mm binocular is considerably heavier.
Field of view
That is written elsewhere on the binocular. It is important to note that you can have two binoculars with the same magnification and lens size but different field of view based on the design of the eyepiece.
The field of view is the angle you can see through the binocular. Say it has a 7A field of view. That would mean that that you can see 7 degrees through it, as opposed to the normal human binocular field of view for a pair of eyes which is 200A wide.
Wide angle binoculars are6considered to be 7A or more while standard field of view for perhaps a 10x50 binocular is about 5A to 7A.
As magnification increases, the field of view decreases. So, a 20x80 binocular would have a narrower field of view than a 10x50 because you see smaller objects that farther off as closer when you zoom in twenty times.
This is the distance to where your eye should sit. For a person wearing glasses, there is physical constraint because you cannot get all the way to where your eye should be. You therefore want something with a long eye relief.
There are binoculars with rotating cups that you can adjust to the appropriate distance when you are wearing glasses and have your eyes at the correct spot so that you can use them while wearing glasses. Long eye relief is considered to between 13 mm to 15 mm eye reliefs and if you wear glasses, do not use any binocular that has an eye relief smaller than that.
Coating on the lenses
Anti-reflective coating is important to ensure no light is lost when looking through a binocular. Consider a window pane. You can see a reflection on a window pane because it is not coated with anti-reflected coating and does not therefore allow all the light through. A binocular has many pieces of glass and by the time light gets through them, if not coated, a lot of visual information has been lost. Some binoculars are fully coated or fully multi-coated (coated on both sides on each lens) and fully multi-coated is by far the best.
You are now caught up on the essentials and can now take a look at various binoculars and what they are useful for.
1. Compact binocular
Compact refers to the size of the lens and so a compact binocular would be anywhere smaller than 30 millimeters. An 8x25 or a 10x25 are the same lens size but slightly different magnification.
Compact lenses are good for hiking and similar situations where you do not want to carry around a lot of weight. They are only good for daylight conditions though, because at night, a lot lighter should be let in to ensure you can see what you need to see. They are therefore not very useful for astronomy or night time viewing. But they are compact and easy to carry in your pocket or purse.
2. The 8x42 or 10x42 (standard binocular)
This is the standard, most popular binocular because it is great for most situations. You can use it in lower light situations such as twilight or dusk and you can use it for general nature watching and bird watching.
It is not so heavy as to have you encumbered as you travel or need a tripod for viewing and not so small as not to let enough visual information in. Whether to choose the 8x magnification or the 10x magnification may seem like an obvious choice in favor of the 10 but higher magnification reduces your field of view as mentioned before.
It makes it more difficult to look at something large yet far away or something like a flock of birds in the air without moving around a lot. With the slightly lower magnification of the 8x42 you can take the whole view in more easily. Higher magnification is also more difficult to keep stable. So, the 8x42 will be less shaky than the 10x.
3. The 10x50 (medium binocular)
A 10x50 is larger and certainly heavier than the previous sizes but has the advantage of taking in more light. What it provides is therefore a better view both in the daylight and at night. It is very effective for bird and nature watching and even more useful for astronomy. Brighter objects appear in more detail and you can view the Milky May, the Andromeda galaxy and the moon in much better detail. It will not require a tripod because it is still light weight and can still be carried around easily.
4. The 20x80 (large binocular)
This has twice the magnification of the last one and a much larger lens, making it really good for high power viewing and astronomy. You can zoom in on far away objects in the daylight much more easily and see in greater detail the night sky objects. Star clusters, nebulae, far off galaxies all come into view. The only disadvantage is its weight which makes it difficult to hold steady by hand and makes it even shakier at that high magnification. A tripod therefore becomes absolutely necessary if you intend to enjoy your viewing and it comes ready with a provision for affixing it to your tripod. The weight also makes it more difficult to carry around.
So, choosing a binocular really depends on what you want to use it for and whether you can use it in that way based on its features. They all have pros and cons. Choose wisely.