Notes on Cameras for Photography

Practical Photojournalism by Martin Keane

·         Visible light 400 nm to 7860 nm

·         P3 when rays of light diverging from a point fall on a lens they are focused oo produce an image

·         The distance from the lens to the plane in which parallel light is brought into focus is known as the focus length of the lens

·         The greater the focal length the larger the size of objects in the image created

·         P6 A lens needs to be moved relative to the image plane to compensate for changes in distance between it and the subject

·         P7 lenses using internal focusing are sometimes designated IF

·         Aperture is the amount of light that a lens will pass

·         Settings of aperture are conventionally: 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32

·         The smaller the number the greater the amount of light passed by the lens

·         Each setting passes half the light of the next setting numerically smaller than it

·         P8 a reduction in the physical size of the aperture when taking the picture i.e choosing a bigger number (stopping down) will mean less light coming through the lens which has to compensated by longer exposure (more camera shake) or etc… it also increases the depth of field

·         Focal length divided by its effective diameter

·         As shutter speeds vary by a factor of 2

·         To pass twice as much light, the diameter of the lens has to be increased, not by a factor of 2, but by a factor of the square root of 2 (=approx. 1.4)