Glossary A to E

110 filmA very small film format, held in a light-proof cartridge designed for easy loading. Now obsolete
117 filmThe film is the same size as 120 film but the spool is much smaller.
120 size filmRoll film that measures 60 mm across and is long enough for 8 off 6×9, 12 off 6×6 or 16 off 6×4.5 negatives. Still available.
126 filmFilm slightly smaller than 35 mm in an easy-load cartridgewhich can be removed mid-roll. It gives a square negative. Now obsolete.
127 filmRoll film that measures 46 mm across and is long enough for 8 off 4×6, 12 off 4×4 or 16 off 4×3 negatives. Now obsolete.
220 filmThe same size film as 120 film but the backing paper is not continuous for the length of the film – so there are no frame numbers for most of the film.
35 mm filmSmall 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.
620 filmThe same film as 120 film but on a smaller spool
828 film35 mm film. Originally with one perforation per frame, later versions had no perforations. The film had numbered backing paper.
Absolute apertureThis is the physical hole in the lens through which the light passes. The absolute aperture is important when considering diffraction effects as it is this, rather than the relative aperture (or ƒ/number) that is important.
Accessory shoeA 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.
apertureThe 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.
Aperture scaleThe sequence of apertures available on a manually adjusted diaphragm. The earliest was the US system but this was replaced by the ƒ/number system. 
APS filmAdvanced Photo System. The film is 24 mm wide. The APS cameras could record photographs in one of three formats – H, C, P – but the cameras actually recorded all photographs in the H format (30.2 × 16.7 mm). The C and P formats only came into force at the printing stage when the H format image would be masked to C or P formats. 
ASAAn American standard for film speeds. It is arithmetic, so double the ASA number indicates double the film speed. Superseded by ISO.
Automatic diaphragmAn 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 exposureA system whereby the camera decides on what combination of aperture and shutter speed to use.
automatic focusingA system where the camera focusses the lens on the subject behind one of several pre-set focus points.
BA shutter speed setting that allows the shutter to remain open while the shutter release button is being held down. Used for timed exposures of over one second.
baseboardThe hinged ‘door’ of a folding camera that holds the lens and shutter in place.
bayonet mounta 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.
bellowsa leather or fabric tunnel between the lens and the camera body that collapses when the camera is closed.
BIIThe German name for 120 film.
Body capA blanking cap that fits to the camera body when the lens is removed to prevent dirt and small items getting into the camera.
Body releasea shutter release on the body of the camera rather than on the shutter housing. This became normal from the mid 1930s.
bokehA Japanese word used to describe the out-of-focus areas of an image. Currently very fashionable but unheard of a few years ago.
Bolta filmUnperforated 35 mm film with backing paper.
brilliant finderA small viewfinder viewed from above and gives an image that is reversed left to right.
Bright lineThese 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 flashThis is a flash system that uses bulbs contains a metal filament which burns to give the light. It is necessary 
bulb releasesimilar 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 film35 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 releasea 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. This was introduced by the German firm of Gauthier.
Characteristic curveAnother name for the density/Log. E curve. A graph plotted of image density against the exposure values that produced them.
cartridgea disposable light-proof container for film. The most common are 126 and 110. Both are disposable.
cassetteA 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
CdS meterCdS stands for Cadmium Sulphide. This is used in light meters as the electrical conductivity of CdS is proportional to the intensity of light falling on it. The main advantage of CdS is that it is sensitive in low light situations. The disadvantage is that it requires a power source.
chromea slang word for colour slide/reversal film
CoatingPutting a layer of coloured material on a lens to reduce flare 
Cocking leverA 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.
Colour balanceColour film is made from several layers of light sensitive emulsion each of which is sensitive to different colours. By adjusting the sensitivity of each layer, the film can be altered to give the colours we see in sunlight although the exposure was with artificial light.
contact printA print of a photograph on paper the same size as the negative.
ContrastDensity range or gradation irrespective of productive conditions. See Gamma.
CoupledUsed 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’
DensityIn film photography, the measured quantity of silver deposited in a negative per unit area.
depth of fieldthe 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 shutterOn 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.
diaphragmA 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.
diffractionAn optical effect caused by light passing by a light proof edge. At small f/ numbers, diffraction will cause visible softening of the image.
DINA German film speed standard. It is logarithmic – an increase in 3 doubles the speed of the film. Superseded by ISO.
disc filmA short-lived type of film with small negatives arrayed around a card disc.
double exposure lockOnce the shutter has been tripped, the shutter is locked until the film has been wound one.
Double-extension bellowsThese 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.
DXThis was a crude bar-code printed on film cassettes so that the camera could automatically read the film speed. As well as film speed, the code recorded film length and exposure tolerance but these last two remained unused by most cameras.
Electronic flashA 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 shutterA 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.
ElementEach of the separate pieces of glass in a lens is referred to as an element.
emulsionthe light sensitive coating on film
EV settingsa 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.
EversetA type of shutter mechanism that is always ready for use and does not need cocking. Everset shutters typically only offer two or three shutter speeds and sometimes only one.
Extension tubesTubes 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.
ExposureAllowing the light to reach the film. Also used to express the amount of light allowed to reach the film – the product of light intensity and time.
exposure compensationA way of over-riding automatic exposure systems where the user can decide to over or under expose the picture by a set amount.
exposure lockAllows 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 metera device to measure the amount of light so a good exposure can be calculated – most include a calculator. See light meter