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Calculating the aperture / opening angle

Entocentric lenses have a fixed aperture (opening) angle. Therefore the object field to be viewed can be increased or reduced by increasing or reducing the working distance.
If the aperture angle is very large, a strong distortion of the optics must usually be expected.

Calculating the opening angle using sensor size and focal length

2w = 2 * arctan (y´/ 2 * 1 / f´) (in rad)

Note: For a simple calculation please select a value from the drop-down box. Even when using the drop-down lists own values can be entered. Please use the first entry "user def."!


Sensor size:
Focal length of lens:
Calculated aperture angle of lens:


We respect your privacy: we do not store any input, results or recipients. Send yourself your calculation with your own email program (MailTo-Link).



Calculation of opening angle from working distance and object size (FOV)

Working distance in mm:
Field of view / object size:
Calculated opening angle:


We respect your privacy: we do not store any input, results or recipients. Send yourself your calculation with your own email program (MailTo-Link).

Attention: The calculated aperture angles are based on simple geometric formulas. The calculated values ​​differ widely from reality for extreme wide angle and fisheye lenses. Please consult the manufacturer's data sheets. Calculated aperture angles below 0.1 as well as beyond 178 degrees are declared invalid.

Further details on optical calculations can be found in chapter Optical basics under "Entocentric lenses" on the subject of picture angle.

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