Angle of View

The "angle of view" is the measure of a given lens' angle of view for a given film format. For example, a 50mm lens can see a 47° view on a 35mm camera, and an 81° view on a 6×6 camera. Several problems are expresed in terms of angle of view:

1. What focal length lens on a 4×5 view camera would be equivalent to a 35mm camera's 50mm lens? (Answer: About 180mm.)
2. Given that the full moon is half a degree wide as seen from the Earth, how long a lens will I have to use to capture an image of the moon that fills half the width of the frame, using a 35mm camera? (Answer: About 2000mm.)
3. If I place my 6×7 medium format camera in the corner of a room, how wide a lens will I need to capture the entire room wall-to-wall, in landscape orientation? (Answer: At least 30mm.)

Formula Used

The angle of view is calculated as:

where F is the length of the frame in the direction for which you want the angle measurement, and f is the focal length of the lens. Both values must be in the same unit, such as millimeters.