What is focal length ? Explain in diagram about focus length.
1 Answer
The distance between the optical center and the principal focus of a lens is called the focal length.
It is denoted by f .
The focal length of convex lens is positive and that of concave lens is negative.
The focal length of an optical system is a measure of how strongly the system converges or diverges light; it is the inverse of the system's optical power.The focal length of the lens is the distance between the lens and the image sensor when the subject is in focus, usually stated in millimeters (e.g., 28 mm, 50 mm, or 100 mm). In the case of zoom lenses, both the minimum and maximum focal lengths are stated, for example 18–55 mm.The lower the focal length number, like 11 or 14 or 24, the more of the scene in front of you gets included in the frame. If you want to fill the frame with a small portion of the scene in front of you, use higher-number focal lengths, like 100, 200 or 400.
The minimum focus distance is the shortest distance at which a lens can focus. In the case of DSLR Cameras, the distance to the subject is measured from the focal plane mark on the camera body, not from the front of the lens.Focal length, usually represented in millimeters (mm), is the basic description of a photographic lens. ... The longer the focal length, the narrower the angle of view and the higher the magnification. The shorter the focal length, the wider the angle of view and the lower the magnification.
Magnification is the ratio between an object's real size and the size at which a lens can project it onto the sensor. This is a function of focal length and the closest distance at which the lens can focus. ... Zoom is the ratio between the smallest and largest focal lengths in a lens where it's variable.