Lens Calculator
How to find the focal length
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| f | focal |
|---|---|
| h | object vertical dimension |
| l | object horizontal dimension |
| D | object distance from lens |
| How to find the focal length | |||||
| Sensor format | 1" | 2/3" | 1/2" | 1/3" | 1/4" |
| Knowing the height of the viewed object | f= 9.6 D/h | f= 6.6 D/h | f= 4.8 D/h | f= 3.6 D/h | f= 2.4 D/h |
| Knowing the width of the viewed object | f= 12.7 D/l | f= 8.8 D/l | f= 6.4 D/l | f= 4.8 D/l | f= 3.4 D/h |
| How to find the object dimensions | |||||
| Sensor format | 1" | 2/3" | 1/2" | 1/3" | 1/4" |
| To calculate the height of the viewed object. | h= 9.6 D/f | h= 6.6 D/f | h= 4.8 D/f | h= 3.6 D/f | h= 2.4 D/f |
| To calculate the width of the viewed object. | l= 12.7 D/f | l= 8.8 D/f | l= 6.4 D/f | l= 4.8 D/f | l= 3.4 D/f |
| Police Guidelines | ||
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| Type of view | Height | This is based on... |
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| Identification | 1.33m | 1.6m man = 120% screen height |
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| Recognition | 3.2m | 1.6m man = 50% screen height |
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| Detection | 16m | 1.6m man = 10% screen height |
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| Monitoring | 32m | 1.6m man = 5% screen height |
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