Calculating an Angle of View with Focal Length

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TN-AC-0027 Calculating an Angle of View with Focal Length Type of lens - By Focal Length : Varifocal Lens, Fixed Focal Lens - By Angle : Wide-angle lens(55 or more), Standard lens(50 ~55), Telephoto lens(50 or less) - By Mount : C Mount, CS Mount, D Mount, S Mount Focal Length(Length) - Focal Length : Distance from lens’ center to camera’s sensor imaging surface. - Shorter focal length means wide-angle lens, and longer local length means a telephoto lens. - Therefore, the focal length of the lens decides the angle of view. To get wider angle, you should use wide-angle lens having shorter focal length. And using the telephoto lens will enable to enlarge the object size from of distance. Image Sensor The 2nd nordal point Focal Length Standard Lens Wide-angle Lens Telephoto Lens Varifocal Lens - The focal length can be changed. - For example, in case of 2.8~10.0mm lens, its focal length can be adjusted by the user’s choice. Fixed Focus lens - The focal length of the lens is fixed - Because it has a fixed focal length, the angle of view can not be changed. TN-AC-0027 Selecting an Angle of View - Angle of view is determined by the focal length of lens, and the size of the camera’s image sensor. - Angle of view of camera generally means the diagonal angle. - For example, if a sensor’s diagonal length is 6mm, the angle of view can be calculated as follows. Angle of View = 2 x tan-1(Diagonal length of the senor / (2 x focal length)) f = 2.8mm : 2 x tan-1(6 / (2 x 2.8)) = 94 -1 f = 10mm : 2 x tan (6 / (2 x 10)) = 33 -1 f = 50mm : 2 x tan (6 / (2 x 50)) = 7 Finding the focal length - The calculation of focal length is as follows: Focal Length = (Distance from camera to the object / Object’s diagonal length) x diagonal length of the sensor - For example, there is an object sized 5m diagonal which is also 5m away from the camera. And the user wants to shoot with full screen and then the focal length should be set as below. f = 5 / 5 x 6 = 6mm - If the object is 50m away from the camera with diagonal size of 5m and the user wants to shoot with full screen, the calculation is as below. f = 50 / 5 x 6 = 60mm .

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