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# Lens calculator - Calculating the aperture 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.

using sensor size
and focal length
using working dist.
and object size

## 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: User def. sensor (mm) 1/4" 3.2 mm 1/3" 4.8 mm 1/2.5" 5.7 mm 1/2" 6.4 mm 1/1.8" 7.2 mm 2/3" 8.8mm 10.5 mm 1" 12.8 mm 1.2" 14.2 mm 15.3 mm 4/3 17.9 mm APS/C 23.7 mm KB 36.0 mm Line .5K 14µm Line 1K 10µm Line 1K 14µm Line 2K 10µm Line 2K 14µm Line 4K 7µm Line 4K 10µm Line 6K 7µm Line 8K 7µm Line 12K 5µm Focal length of lens: Userdef. (mm) 2.8 3.2 4.8 6 8 9 12 16 17 23 25 35 50 60 75 85 100 125 150 Calculated aperture angle of lens:

## Calculating the opening angle using working distance and object size (FOV)

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

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.