Formula
The sensor fills the frame at the focal length:
degrees = 2 × atan(sensor width / (2 × focal length))
The crop-factor page multiplies a focal length by a crop. It does not return an angle.
Assumptions
- The lens is rectilinear.
- Sensor width is the horizontal size of the imaging area.
- Focus is at infinity for this thin-lens angle.
Worked example
A 50 mm lens on a 36 mm sensor sees 39.6° across.
Input definitions
- Focal length
- The lens focal length in millimetres.
- Sensor width
- The horizontal size of the sensor. A full-frame sensor is 36 mm wide.
Limitations
This is a planning figure from the numbers you type. It is not a measurement of a network, a camera, a printer, or a power supply.
Questions
Why is this not the crop factor?
Crop factor rescales a focal length into a full-frame equivalent. This page returns the angle on the sensor you type.
What sensor width is full frame?
36 mm across. A smaller sensor needs the width of that sensor, not 36.