Binoculars.org

You can’t have both. High magnification - huge field of view. A compact body design with lots of light gathering ability, sorry, you just can’t have both.

After nearly a decade of talking to customers about their needs for a binocular, this is the first thing we talk about when helping a customer select their binoculars. Let’s use the example of selecting a binocular for watching sporting events - say football for example.

For this post to be helpful, you should already understand some basics of binoculars - what the “8″ in 8×42 means, and what “25″ in 8×25 means. The number before the “x” is the binoculars magnification, and the number after the “x” is the binoculars objective lens (outside lens) size in millimeters. An 8×25 binocular has 8 times magnification and a 25mm objective lens.

So our football enthusiast wants a binocular for viewing from the upper-deck seats. A binocular that is compact, and can bring the action in really close - Oh, and wants a nice large field of view. Let’s talk about some of the “rules” of binocular selection and see why we may not be able to get everything on the list.

Binocular Size

A binoculars physical size is determined by its objective lens. An 8×25 binocular and an 8×40 binocular both will see the same 8x magnified view, however the 8×25 will have smaller 25mm objective lenses and this means a smaller, compact body design. The 8×40 binocular will have larger 40mm objective lenses, giving the binocular a larger body design.

Binocular Light Gathering

A binoculars objective lens size determines how much light the binocular can gather. The larger the lens the more light the binocular can take in, giving you brighter images. A binoculars magnification also has an effect on the brightness of the image - if the objective lens size stays the same, the more you magnify, the dimmer the image will be.

Binocular Field of View

The field of view of the binocular is generally determined by its magnification. Binoculars with smaller magnifications have larger fields of view. The more you magnify, the field of view is decreased. Its a give and take. Binocular field of view is measured in “feet at 1000 yards”. For example, if a binoculars field of view is measured 310 feet @ 1000 yards, a great way to visualize this is to imagine a fence thats 1000 yards away from you and is infinitely wide from left to right. When you look at that fence in your binoculars, you will see 310 feet of that fence.

Now the rules start to come into play

Now that we have an understanding of a binoculars physical size, its magnification and objective lens and its field of view, we can now use this to lay out some basic rules to follow when selecting a pair of binoculars. These rules will also help understand why you can’t always have everything in a binocular.

With our example of finding a binocular for watching football games we can now break down some of the decisions that need to be made. If you wanted a compact binocular because you don’t want to lug around something too large and just want something that fits simply into a jacket pocket, then you are going to have to give up on light gathering. If you also want a binocular with a high magnification power yet want to see a large field of view, you are going to have to find a balance between either magnification or field of view.

Start with size - then magnification

The first thing you should consider when you select a binocular is what you are going to use them for. Then ask yourself, when I do that activity, what size object am I willing to take along with me. Start by deciding on a binoculars physical size, then work into the rest. After selecting your size, then decide on what magnificaion is best for your use. Many binocular uses have standard magnifications that are best for that use.

Remember, what good is a pair of binoculars if they are a chore to take with you.