Field of View Calculator

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Field of View (FOV) Calculator

Common: Full Frame = 36mm, APS-C = 23.6mm, Micro 4/3 = 17.3mm

Calculation Results

Horizontal Angle of View

Field Width at Distance

function calculateFOV() { var sensorWidth = parseFloat(document.getElementById('sensorWidth').value); var focalLength = parseFloat(document.getElementById('focalLength').value); var distance = parseFloat(document.getElementById('subjectDistance').value); var resultDiv = document.getElementById('fov-results'); var angleDisplay = document.getElementById('angleResult'); var widthDisplay = document.getElementById('widthResult'); if (isNaN(sensorWidth) || isNaN(focalLength) || isNaN(distance) || focalLength <= 0 || sensorWidth <= 0 || distance < 0) { alert("Please enter valid positive numbers for sensor width, focal length, and distance."); return; } // Calculation for Angular FOV: α = 2 * arctan(h / (2 * f)) var angleRad = 2 * Math.atan(sensorWidth / (2 * focalLength)); var angleDeg = angleRad * (180 / Math.PI); // Calculation for Linear FOV at distance: W = 2 * d * tan(α / 2) // Or more simply: W = (sensorWidth * distance * 1000) / focalLength (converting distance to mm then back to m) // But we use the trigonometric approach for consistency var fieldWidth = 2 * distance * Math.tan(angleRad / 2); angleDisplay.innerHTML = angleDeg.toFixed(2) + "°"; widthDisplay.innerHTML = fieldWidth.toFixed(2) + " meters"; resultDiv.style.display = 'block'; }

Understanding the Field of View (FOV)

The Field of View (FOV) is a critical concept in photography, cinematography, and surveillance. It describes the extent of the observable world that is seen through a camera lens at any given moment. Understanding FOV helps photographers choose the right lens for a landscape, architects plan security camera coverage, and hobbyists understand their telescope's capabilities.

How FOV is Calculated

The field of view is determined by two primary hardware factors: the physical size of the camera sensor and the focal length of the lens. The relationship is expressed through trigonometry:

  • Angular FOV: Calculated as 2 × arctan(Sensor Dimension / (2 × Focal Length)).
  • Linear FOV: The actual width or height of the area captured at a specific distance from the lens.

Key Variables Explained

To use the FOV calculator effectively, you should understand these three inputs:

  1. Sensor Width: This is the horizontal measurement of your camera's imaging sensor. A "Full Frame" sensor is typically 36mm wide. APS-C sensors (found in many DSLRs) are roughly 23.6mm, and smartphones have much smaller sensors (often around 5-7mm).
  2. Focal Length: Usually measured in millimeters (mm), this is printed on your lens. A smaller focal length (e.g., 14mm) provides a wide FOV, while a larger focal length (e.g., 200mm) provides a narrow, zoomed-in FOV.
  3. Distance to Subject: This determines the "Linear Field of View." While the angle of the lens stays the same, the actual area you see increases as you move further away from the subject.

Practical Example

Imagine you are using a standard Full Frame camera (36mm sensor) with a 50mm lens (often called a 'nifty fifty'). If you are standing 5 meters away from a group of people:

  • Input: Sensor: 36mm | Focal Length: 50mm | Distance: 5m
  • Result: Your horizontal angle of view will be approximately 39.6°.
  • Result: At 5 meters away, you will be able to see a width of 3.6 meters in your frame.

If you switched to a 24mm wide-angle lens from the same distance, your angle of view would jump to roughly 73.7°, and you would see 7.5 meters of width—nearly double the scene!

Why This Matters

Knowing your FOV is essential for several professional applications:

  • Security Systems: Ensuring a camera covers an entire hallway or parking lot without "blind spots."
  • Real Estate Photography: Choosing wide-angle lenses to make small rooms appear more spacious.
  • Astronomy: Calculating how much of the night sky or a specific nebula will fit into a telescope's eyepiece or camera sensor.
  • VFX & CGI: Matching virtual cameras in 3D software to real-world footage for seamless visual effects integration.

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