Edmund Optics FOV Calculator: How to Use It

The Edmund Optics FOV (Field of View) calculator is a free online tool that estimates the angular or linear field of view for a given lens and sensor combination. You enter the sensor dimensions and focal length, and it returns the horizontal, vertical, and diagonal field of view in degrees. It is a quick way to check if a lens will cover your target area before buying or building a vision system.

Formula

The calculator uses the basic geometric relationship between the sensor size, focal length, and field of view. For a rectilinear lens (the most common type), the half-angle is the arctangent of half the sensor dimension divided by the focal length. Doubling that gives the full field of view.

Horizontal FOV = 2 × arctan( (sensor width / 2) / focal length )

Vertical FOV = 2 × arctan( (sensor height / 2) / focal length )

Diagonal FOV = 2 × arctan( (sensor diagonal / 2) / focal length )

Units: sensor dimensions in millimeters (mm), focal length in millimeters (mm), and the result is in degrees. The sensor diagonal is √(width² + height²).

Worked Example

Using the calculator defaults: a sensor width of 6.4 mm, height of 4.8 mm (a 1/2.5″-type sensor), and a 12 mm focal length lens.

1. Half the sensor width: 6.4 / 2 = 3.2 mm
2. Divide by focal length: 3.2 / 12 = 0.2667
3. Arctangent of that: atan(0.2667) = 14.93° (approximately)
4. Double it: 2 × 14.93 = 29.86°

So the horizontal FOV is about 29.9°. Similarly, the vertical FOV is 2 × atan(2.4/12) = 22.6°, and the diagonal is 2 × atan(4.0/12) = 36.9°. These match the calculator output.

When to Use the FOV Calculator

Use this calculator when you need to know how much of a scene a camera will capture at a certain distance, or when comparing lenses for a machine vision application. Typical scenarios include:

• Selecting a lens for a fixed-mount camera inspecting parts on a conveyor.
• Estimating the coverage area of a surveillance camera at a given mounting height.
• Checking if a lens will fit the sensor size of your camera without vignetting.
• Planning a multi-camera setup where adjacent fields of view must overlap.

The calculator works for any lens that behaves as a rectilinear projection, which includes most standard machine vision and CCTV lenses. For fisheye or other wide-angle lenses with strong distortion, the simple formula is not accurate.

How to Read the Result

The result gives you the angular field of view in degrees. To get the linear field of view (the width or height of the area seen at a given distance), use the formula:

Linear FOV = 2 × distance × tan(angular FOV / 2)

For example, with the default 29.9° horizontal FOV at a distance of 1 meter (1000 mm), the horizontal coverage is 2 × 1000 × tan(14.95°) = 534 mm. So the camera sees a width of about 0.53 m at that distance.

Remember that the FOV is measured at the object plane, not at the lens. The distance is measured from the lens’s front principal point, which is close to the front of the lens barrel for most fixed focal length lenses.

Common Mistakes and Misconceptions

One common mistake is using the sensor size in inches (like 1/3″) directly. The inch designation is a legacy tube size, not the actual sensor diagonal. Always use the actual width and height in millimeters from the sensor datasheet.

Another error is confusing horizontal and vertical FOV. The calculator gives both, but many people only note the horizontal value. If you are checking a lens for a specific object height, you need the vertical FOV.

Also, the formula assumes the lens has no distortion. Real lenses have some distortion, especially at wide angles, so the actual FOV may differ by a few percent. For critical applications, you should verify with a calibration target.

Finally, the calculator does not account for the lens’s image circle. A lens designed for a smaller sensor will not cover a larger sensor, even if the FOV calculation seems to work. The image circle must be at least the sensor diagonal.

Alternatives and Related Tools

Edmund Optics provides its own FOV calculator on its website, but there are other free tools with similar functions. Some allow you to enter the working distance and object size to find the required focal length, which is the inverse problem. Others include a database of sensors and lenses for quick selection.

If you need to account for distortion, you might need a more advanced optical design tool or a camera calibration software. For most basic lens selection, the simple arctangent formula is sufficient.

Frequently Asked Questions

What is the difference between angular FOV and linear FOV?

Angular FOV is the angle of view in degrees, which is a property of the lens and sensor. Linear FOV is the actual width or height of the scene at a specific distance, usually in meters or feet. You can convert between them using the tangent function as shown above.

Why does the calculator need sensor dimensions in mm?

Because the focal length is also in mm. The formula uses the ratio of sensor size to focal length, so both must be in the same units. Using the sensor’s inch designation (like 1/2.5″) would give incorrect results because that number is not the actual size.

Can I use this calculator for a smartphone camera?

Yes, but you need to know the sensor size and focal length of the phone’s camera, which are rarely published. Some phone specs list the sensor size, but focal length is often given in 35mm equivalent, which you cannot use directly. You would need the actual focal length in mm.

Does the FOV change with focus distance?

Yes, slightly. The formula assumes focus at infinity. When focusing closer, the effective focal length can change, and the FOV may become narrower. For most practical purposes, the difference is small unless you are doing macro work.

What if my lens has a different projection (fisheye)?

For fisheye lenses, the field of view is larger than the rectilinear formula predicts. You would need a different model, such as the equidistant or equisolid angle projection. The calculator here is only for rectilinear lenses.

Related

• Area of a Circle Sector Calculator & Formula
• Area of a Circle Calculator with Radius
• Area and Perimeter of Circle Calculator

in sensor_w | Sensor width (mm) | mm | 6.4 | 0
in sensor_h | Sensor height (mm) | mm | 4.8 | 0
in focal | Focal length (mm) | mm | 12 | 0
out fov_h | Horizontal FOV | degrees | 2 * atand((sensor_w / 2) / focal) | 2
out fov_v | Vertical FOV | degrees | 2 * atand((sensor_h / 2) / focal) | 2
out fov_d | Diagonal FOV | degrees | 2 * atand((sqrt(sensor_w^2 + sensor_h^2) / 2) / focal) | 2