Focal lenght

To capture an image light has to pass thru the lens onto the film/sensor which records the image. Light has to be “focused” from the subject into the camera. The feature on the camera that allows this is the lens. The lens is a made up of curved glass which allows the light entering the camera , to converge at a point, this area of focus is referred to as the focal point of the lens.





As well as directing the light onto the recording material in a camera the lens also captures that image in many different angles and levels of sharpness.

Photographic lenses are recognised by their focal length, which is measured in millimetres. The focal length is the distance from the rear of the lens element to the film plane, when the lens is focused on infinity. Wide-angle lenses (18 to 35mm) are used to capture the full frame of the subject, though there is some distortion on the images captured as perspective is altered. Standard lenses (50mm) on a 35mm camera, allow wide framing with reasonable picture quality. The 50mm lens gives the photographer the same field of view as the human eye. Telescopic lenses (85-300mm) allow the photographer to fill the frame from a distant viewpoint. The most distinctive quality of a telephoto lens is its increased magnification levels. Telephoto lenses unfortunately alter the perspective of an image as objects appear closer together. Modern lenses are combined together which allows the photographer to move the lens thru many different focal lengths.


EXERCISE FOCAL LENGTHS


The seris of images below show an example of the same image taken at different focal lenghts.



24mm




































35mm

































50mm






















70mm