angle of view – the area that is shown by a lens. The standard used is that from a 135 film camera, expressed in as a focal length as millimetres (mm). A lens of focal length of 50mm is called a standard lens. Lenses with a focal length of 35mm or less are called wide angle lenses.
aperture – the control of the physical opening of a lens of the amount of light to reach the film or sensor.
APS-C format – a film and sensor format smaller than 35mm but larger than micro four-thirds. Dimensions are 25.1×16.7mm.
crop factor – the “multiplier” to convert from full-frame format. To convert between APS-C from full-frame multiply, for example, the focal length (18mm) by the multiplier (1.5). This tells you that the equivalent angle of view is 27mm on a full-frame format camera.
depth-of-field – the amount of area which is in focus with regards to aperture. The smaller the aperture greater the area that is in focus.
DSLR – acronym for digital single lens reflex.
exposure – the combination of aperture, shutter speed and ISO which gives the “best” overall image.
full-frame format – 35x24mm film or sensor. Taken to be the standard because of its ubiquity and versatility.
ISO – the sensitivity of film or sensor.
single lens reflex
twin lens reflex
wide angle lens