GamerBoy (12-05-09),shack khan (07-08-16)
Lens Focal Length
Lens Focal Length may be calculated after determining DISTANCE to SCENE (DS) from CCTV Camera and the WIDTH of SCENE (WS) required at that distance.
Focal Length of Lens = (DISTANCE to SCENE × 4.8) ÷ (WIDTH of SCENE).
All measurements in mm [equation for 1/3" Sensor, 4.8 mm wide × 3.6 mm high]
Focal Length of Lens = (DISTANCE to SCENE × 3.6) ÷ (WIDTH of SCENE).
All measurements in mm [equation for 1/4" Sensor, 3.6 mm wide × 2.7 mm high]
Focal Length of Lens = (DISTANCE to SCENE × 6.4) ÷ (WIDTH of SCENE).
All measurements in mm [equation for 1/2" Sensor, 6.4 mm wide × 4.8 mm high]
For example if DS = 1500mm, WS = 2000mm, Sensor = 1/3" equation is:
(1500 × 4.8) ÷ 2000 = 3.6.
A 3.6 mm focal length lens will provide an on-screen image of a scene 2000 mm wide at a camera distance of 1500 mm. In practice results may vary ± ~15% due to component tolerances, variations in image sensor dimensions and monitor over-scan.
Other transpositions of equation:
To Find:
Width of Scene = (DISTANCE to SCENE × 4.8) ÷ (Focal Length of Lens).
All measurements in mm [equation for 1/3" Sensor, 4.8 mm wide × 3.6 mm high]
Width of Scene = (DISTANCE to SCENE × 3.6) ÷ (Focal Length of Lens).
All measurements in mm [equation for 1/4" Sensor, 3.6 mm wide × 2.7 mm high]
Width of Scene = (DISTANCE to SCENE × 6.4) ÷ (Focal Length of Lens).
All measurements in mm [equation for 1/2" Sensor, 6.4 mm wide × 4.8 mm high]
To Find:
Distance to Scene = (Width of Scene × Focal Length of Lens) ÷ (4.8).
All measurements in mm [equation for 1/3" Sensor, 4.8 mm wide × 3.6 mm high]
Distance to Scene = (Width of Scene × Focal Length of Lens) ÷ (3.6).
All measurements in mm [equation for 1/4" Sensor, 3.6 mm wide × 2.7 mm high]
Distance to Scene = (Width of Scene × Focal Length of Lens) ÷ (6.4).
All measurements in mm [equation for 1/2" Sensor, 6.4 mm wide × 4.8 mm high]
GamerBoy (12-05-09),shack khan (07-08-16)
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