Glossary of Photographic terms (A to E)

110 film	A very small film format, held in a light-proof cartridge designed for easy loading. Now obsolete
120 size film	Roll film that measures 60 mm across and is long enough for 8 off 6x9, 12 off 6x6 or 16 off 6x4.5 negatives. Still available.
126 film	Film slightly smaller than 35 mm in an easy-load cartridge which can be removed mid-roll. It gives a square negative. Now obsolete.
127 film	Roll film that measures 46 mm across and is long enough for 8 off 4x6, 12 off 4x4 or 16 off 4x3 negatives. Now obsolete.
35 mm film	Small film format based on cine film provided in a light proof cassette to allow daylight loading of the camera. Has two rows of perforations used to both locate and to move the film. Image size is usually 24mm by 36mm. Still available.
Accessory shoe	A shoe fitted to the top of the camera to allow accessories to be fitted. In the early days of photography, this was likely to be either a rangefinder or secondary viewfinder. If it includes electrical flash contacts, it is a hot shoe.
aperture	The hole through which light passes to get into the camera. In many cameras, this is adjustable.
aperture priority	An automatic exposure system that allows the user to set the aperture and then calculates the required shutter speed.
ASA	An American standard for film speeds. It is arithmetic, so double the ASA number indicates double the film speed. Superseded by ISO.
Automatic diaphragm	An iris diaphragm that will close down when the shutter release is pressed. They allow for composing and calculating exposure with the lens at its brightest aperture.
automatic exposure	A system whereby the camera decides on what combination of aperture and shutter speed to use.
automatic focusing	A system where the camera focusses the lens on the subject behind one of several pre-set focus points.
baseboard	The hinged 'door' of a folding camera that holds the lens and shutter in place.
bayonet	a system of fitting a removable lens quickly. This only requires about 1/3 of a turn of the lens compared to several turns for a threaded lens.
bellows	a leather or fabric tunnel between the lens and the camera body that collapses when the camera is closed.
BII	The German name for 120 film.
Body cap	A blanking cap that fits to the camera body when the lens is removed to prevent dirt and small items getting into the camera.
Body release	a shutter release on the body of the camera rather than on the shutter housing. This became normal from the mid 1930s.
bokeh	A Japanese word used to describe the out-of-focus areas of an image. Currently very fashionable but unheard of a few years ago.
brilliant finder	A small viewfinder viewed from above and gives an image that is reversed left to right.
Bright line	These are framing lines in the viewfinder which are brighter than the image. Usually include secondary lines for use with close-ups. The field of view is much larger than the bright lines so it is important to keep the subject within the bright lines. Most portraits taken with the heads missing is down to not heeding the bright lines.
Bulb flash	This is a flash system that uses bulbs contains a metal filament which burns to give the light. It is necessary
bulb release	similar to a cable release but is a hollow tube with a pneumatic bulb on the end. The shutter is tripped by squeezing the bulb.
Bulk film	35 mm film can be bought in very long lengths – typically 17 m or longer – allowing the user to cut off (in the dark!) the amount required and manually fit the film into a cassette. This is done both the save money and to allow the use of much smaller film lengths, saving wastage when only a few photographs are required.
cable release	a flexible cable to allow tripping the shutter without touching the camera – this avoids camera shake with slow exposures. The cable is usually wire in a wound metal sleeve. There is a standard thread for cable releases which has a conical thread.
cartridge	a disposable light-proof container for film. The most common are 126 and 110. Both are disposable.
cassette	A holder for film. Usually the Kodak designed cassette still in use but Leica, Zeiss Ikon and Agfa all produced their own designs at one time. See also: 126 and 110 film
chrome	a slang word for colour slide/reversal film
Cocking lever	A lever on leaf shutters that must be set before the shutter can be fired. From the early 1950s, these were replaced by internal cocking mechanisms set by advancing the film.
contact print	A print of a photograph on paper the same size as the negative.
Coupled	Used for both light meters and rangefinders. It means that adjusting the meter alters the exposure setting on the camera or adjusting the rangefinder adjusts the focus on the lens. See ‘uncoupled’
depth of field	the spread of distances in the subject that are in acceptable focus on the negative. Depends on f/ number used and lens focal length.
dial-set shutter	On older manual cameras, a separate dial, usually above the shutter that is used to set the shutter speed. Phased out around 1930. cf rim-set shutter.
diaphragm	A series of interlocking blades that can be moved to make differing sizes of holes to adjust the lens aperture. Often referred to as an iris diaphragm.
diffraction	An optical effect caused by light passing by a light proof edge. At small f/ numbers, diffraction will cause visible softening of the image.
DIN	A German film speed standard. It is logarithmic – an increase in 3 doubles the speed of the film. Superseded by ISO.
disc film	A short-lived type of film with small negatives arrayed around a card disc.
double exposure lock	Once the shutter has been tripped, the shutter is locked until the film has been wound one.
Double-extension bellows	These allow the lens to be moved much further away from the plate/film and so allow the camera to be focussed much closer to the object being photographed. They are an early macro device.
Electronic flash	A type of flash gun using a discharge tube rather than flash bulbs. The light is usually much brighter and colour balanced for colour film. The light is produced instantaneously the gun is fired
Electronic shutter	A computer controlled shutter that is capable of any speed when used by the automatic exposure system, not just the speeds displayed on the speed selector.
emulsion	the light sensitive coating on film
EV settings	a system common in the 1950s and 60s where the shutter speed and aperture were linked in the shutter housing. The user set a EV value on a ring on the shutter housing and could then adjust either speed or aperture and maintain the set exposure.
Extension tubes	Tubes that fit between the camera body and the lens. Moving the lens away from the camera allows the lens to focus much more closely to the subject making extreme close-ups possible.
Exposure	Allowing the light to reach the film. Also used to express the amount of light allowed to reach the film.
exposure compensation	A way of over-riding automatic exposure systems where the user can decide to over or under expose the picture by a set amount.
exposure lock	Allows the camera the set the exposure while pointing away from the subject – for instance to avoid under-exposure if there is a lot of sky in the picture.
exposure meter	a device to measure the amount of light so a good exposure can be calculated – most include a calculator. See light meter