What is the Field of View and How to Calculate it?

Do you know if the field of view is crucial to know when purchasing your rifle scopes or other optics? Is there any relation between the field of view with our scope’s eye relief and magnification? All these and more shall we find out soon.

As you look into your rifle scope, you will see an area of scene. This measured area of scene is what we call the field of view (FOV). Whether you’re bird watching or hunting for a deer, once you have a wide field of view, it will make your hunting game easier. You can easily track moving birds or track a moving deer. So, let’s further look into what is the field of view and how to calculate it in this post.

Getting a good field of view will further enhance how you get a clear shot that can help you nail your target. So, let’s get into what is the field of view and how to calculate it.

What Exactly is the Field of View in Optics?

The field of view (FOV) can be defined as that measured area in a particular scene you’re looking at when you peep into your scope or optics. So, FOV shows you how much of the target view you can see at a specific distance.

In simple terms, FOV is the size of the whole view you see from left to right when you look into your rifle scope from a particular distance.

This field of view is usually determined by several components in optics and these components include the eyepiece, the assembly position, the way the lens are thick, and even magnification. This is why two similar rifle scopes can have a totally different FOV when you peep into the scope. So, it is because of the contours and the shape of the glass that can be found inside the scope.

For scopes, they provide their field of view in feet at 100 yards. Then for binocular, rangefinders, telescope, and spotting scopes, it is done in feet at 1000 yards. So, if you have an optics (say binoculars) that state its FOV is 351 at 1000 yards, this implies that you can view 351 feet of a scene as you look into it from right to left when you’re viewing at 1000 yards.

How magnification affects the field of view

When we talk about magnification, we’re referring to how near or far you view a thing from a distance in contrast to what your naked eyes see. So, looking at a targeted image that is far is done with the help of a scope with some level of magnification. Hence, when you use a scope to view a distant image, you get a closer and clear picture.

Now, one crucial feature that affects the field of view in a rifle scope is magnification. Once the magnification is increased, it will cause the FOV to decrease.

Let’s take this instance; using a magnification of 6x, it will give you a clear view of everything that surrounds your target. However, once the magnification is further increased to say 24x, it will cause the field of view to be lowered because your focus will be more on the target.

So, for instance, using a 3x magnification scope that is variable will give you a FOV of around 30 feet at 100 yards. Then once the magnification goes up to 9x, you can get around 14 feet of FOV.

So, How do I Choose a Good FOV Scope?

For this reason stated above, when it’s time for you to choose a rifle scope for you, go for the model with a higher field of view even when it’s at a higher magnification. Additionally, ensure your rifle scope features a constant FOV which should be proportionate to the level of magnification of your rifle scope.

What Exactly Determines the Field of View in a Scope?

You can determine the FOV of a scope once you know the value of the magnification. Then you combine the value of the magnification with the focal length of the eyepiece and its target. Note that because the level of magnification tends to vary depending on the scope’s manufacturer, the field of view will also vary.  

So, in the process of selecting a rifle scope, you should note that the objective lens diameter shouldn’t be considered as the factor that determines the value of FOV. Objective lens diameter only enhances the transmission of light.

Take for example, when aiming your rifle scope and working on a field of view that is large, it will require a top-notch lens system to be present inside the scope. This is so that the scope can produce a clean and crisp target image.

How to Calculate the FOV For Your Optics Correctly

The field of view measurement given by the manufacturers of optics varies. Take for example, for spotting scopes, rangefinders, and binoculars, their field of view is usually measured in feet at 1000 yards. However, for the FOV of scopes, the measurement is done in feet at 100 yards.

·         Therefore, computing the field of view for binoculars with 213 feet FOV at 1000 yards will generate a viewpoint that is wide as you look from the right view to the left with a viewing distance of 1000 yards. Take note that once the distance is measured in yards, feet, or meters, we call it a linear field of view.

·         Now, in other situations, the measurement of FOV can come in angular degrees. You can have an example that states that the angular field of view for a rangefinder is 6.0 degrees. Take note that the angular field hardly changes due to the target’s distance compared to the linear FOV which tends to increase or decrease with depending on the target distance.

·         It is easy to convert the angular field of view to a linear field of view. You only need to do a multiplication of the angle by 52.5 and you’ll obtain the linear field of vision which will be in feet. Take this example, if you want to compute the distance of a rangefinder that has a FOV of 6.0 degrees, at 1000 yards, what will be done is the multiplication of the degrees which is 6.0 by 52.2 feet. This will help you obtain a resulting linear FOV of 315 feet. Take note that 52.5 feet are equal to one degree of the angle.

Small or Big FOV for shooting: Which Should you go for?

The fact is that different shooters have their various shooting needs and this shooting is done at various ranges. Hence, it’s advisable not to come to the conclusion that a bigger or smaller field of view is required.

The majority of hunters have their shooting games fall in the range of 50 yards to 150 yards. So, judging from this type of shooting distance range, using a higher magnification isn’t really needed. Therefore, because a higher magnification isn’t required for this shooting range, as a hunter, you may only require using a smaller FOV for your shooting tasks.

So, as your targeted animal gets closer to you, you will require a wider view because any little movement from the targeted animal can cause it to go out of view. This usually happens when you’re using a smaller FOV scope.

Usually, you should be needing a broader field of view of your camera for your hunting needs or most of your short range shootings. Furthermore, apart from needing a wider field diameter, you will also require long eye relief. (Eye relief is the distance you give from your eye to your rifle scope’s camera lens or ocular lens when peeping into your scope). So, when you have a wide angle of the field of view, it encourages a more precise target aim.  

When you’re too far or too close outside the recommended eye relief distance, it will affect the way you view your surrounding through your scope. It can cause the field of view to block out some parts of the field of view. In some cases, when you’re too far from the recommended eye relief distance, it can cause shadowing.  

Take for instance, when you want to aim and shoot a perilous animal at a distance range between 50 to 150 yards, the minimum magnification that is recommended is 1x. It is also recommended that you don’t surpass the maximum magnification of 2.5x. This is so that you can have a clean and crisp view.

When you increase the magnification further from the recommended range, this will affect how much of the targeted area you can view. Take note that as your hunt and aim at your target, viewing only your target shouldn’t be the sole aim. It is also recommended that you to be able to view your some area surrounding your target. This will give you good focus distance and further improve your chance of having a great shot.