Glossary of Photographic Terms (O to Z)

orthochromatic	sensitive to blue and green light. The name means 'correct colour'. Orthochromatic film can be handled with a normal darkroom safe-light.
panchromatic	sensitive all colours – the usual film that is currently available. Must be handled in complete darkness.
PC socket	Prontor-Compur. Named after the two most prominent shutter manufacturers from the mid-20th century. It is the standard connector for flash guns found on most cameras until the Hot Shoe became normal.
pentamirror	a cheap alternative for a pentaprism. It does the same job for a much lower price but does not produce as bright an image. Found on more modern and cheaper SLR cameras.
pentaprism	a glass prism inside a reflex viewfinder that turns the image the right way around for viewing. It is found in most SLR cameras.
plate camera	a camera designed to use glass plates rather than film.
Pressure plate	This is a sprung plate, usually attached to the back of the camera, that pushed against the back of the film and helped to keep the film flat against the film gate.
Pull developing	This is reducing the amount of time the film is in the developer to compensate for the film having been overexposed.
Push developing	This is extending the amount of time the film is in the developer to compensate for the film having been underexposed. This allows the user to use the film as if it had a higher DIN/ASA/ISO rating.
rapid cassette	An attempt by Agfa to compete with Kodak's 126 film cartridge. Film was held loosely in the cassette and needed to be wound into an empty Rapid cassette. Used between 1964 and the early 1990s. Almost identical to the Karat cassette.
Red window	A small, round window on the back of a medium format camera to allow the user to see the frame numbers printed on the film backing paper. There may be two windows on half-frame cameras (those taking 6 x 4.5 cm negatives).
Reflex viewing	This is viewing the image through either the taking lens (SLR) or by a secondary lens (TLR), the image seen being the exactly the same as the image on the negative.
Reverse Galilean viewfinder.	This is effectively a small telescope as designed by Galileo used backwards – it makes the view appear smaller so that a large scene can be fitted into a small viewfinder.
rewind knob	On 35 mm cameras, the means of winding the film back into the cassette.
rim-set shutter	On older manual cameras, the ring around the lens that is used to alter the shutter speed. Dates from around 1930. cf Dial set shutter.
rise and fall mechanism	A way of raising the lens so that a different part of the image circle is over the negative. It is used when photographing high objects to avoid tilting the camera.
Self-capping shutter	This is a type of focal plane shutter – the type used in all SLR cameras. In early focal plane shutters, the shutter would stay open when rewound meaning the film plate had to be removed first and it could not be used for film. A self-capping shutter will remain closed while being rewound so can be used with a plate in place and can be used for film.
self-erecting	A camera that unfolds with the lens in the correct position for picture taking at the touch of a button.
self-timer	A device in the shutter that delays the shutter opening for ten seconds or so. Marked as ‘V’ on German cameras.
shutter	The means of letting light into the camera in a controlled way. Either inside the lens (leaf shutter) or in front of the film (focal plane shutter).
shutter cocking lever	On older shutters (pre-1955-ish) a lever used to set the shutter ready for use.
shutter release	The button or lever used to fire the shutter.
Signal	some camera provide a visual signal that the film has been would on and the camera is ready to take the next picture. Usually takes the form of a dot by the film advance that turns red when the camera is ready.
SLR	Single Lens Reflex – a type of camera where the user views the scene through the taking lens to give very accurate composition.
Split image disc	This is frequently found in the centre of a SLR focussing screen. It will split a vertical line (occasionally horizontal or diagonal line) while it is out of focus, the line joining itself at the point of focus.
spool	A wooden, metal or plastic holder for rolls of film.
spool carriers	The part of the camera that holds the spool of film either ready for use or once used.
sprocket hole	the row of hole along the edge of film to allow the camera to move it. In 35mm film there is a row on either edge. In 126 cartridges there is only one row of sprocket holes.
Standard lens	A lens that approximates the angle of view of the human eye. In 35mm photography, this is taken to be 43 mm (the diagonal of the negative). The ‘kit’ lens usually provided with 35 mm SLR cameras was 50mm. Fixed lens cameras were usually nearer to 40mm.
Stand development	This is a technique where the film is developed with no agitation and extending the development time to half an hour or even longer. This is useful where the speed of the film is not known or where the user might suspect exposure problems. It will usually produce a usable negative but not an excellent one.
Stereo attachment	These allow the camera to produce two images on one frame of film, each from a slightly different perspective. When the picture is viewed on a stereoscope, the image appears to be three dimensional.
Sunny 16	A rule of thumb for estimating the exposure where no light meter is available. The basis is to set the aperture to f/16 and the shutter speed to the reciprocal of the film speed (ISO 50 = shutter speed 1/50, ISO 200 = shutter speed 1/200). Works well on a bright sunny day.
Telephoto	A lens that is shorter than its focal length. The term gets used (incorrectly) for any long-focus lens. A 300 mm lens will have the lens node 300 mm from the film. A 300 mm telephoto lens will have its node in front of the lens – the node will still be 300 mm from the film but the physical lens will be shorter than 300 mm.
TLR	Twin Lens Reflex – a type of camera that has two identical lenses, one above the other. Both are focused by the same mechanism at the same time allowing for accurate focusing but at the cost of some parallax error in near shots.
tripod boss	A threaded hole to allow the camera to be fitted to a tripod. On older cameras it will be either 3/8 inch or ¼ inch Whitworth thread and on more modern cameras 3/8 or ¼ UNC thread. For this purpose, Whitworth and UNC are interchangeable.
TTL	Through The Lens – a light metering system that measures the light that is coming in the lens. This gives more accurate exposures than using a hand-held light meter will.
Uncoupled	Used of light meters and rangefinders where adjusting the meter or rangefinder gives a reading which the user must transfer to the camera lens or shutter manually. Cf ‘coupled’
V	Vorlaufwerk which is German for self-timer.
vignetting	A darkening at the edges of the picture caused by the image circle being too close in size to the negative – Common with cheaper lenses.
Waist-level finder	A viewfinder that is used at waist-level rather than eye-level. Frequent on medium format cameras, particularly TLR cameras but also occasionally on 35 mm cameras.
Waterhouse stops	a sequence of holes of varying sizes either in a line or around a disc that can be moved in front of the lens to control the amount of light entering the camera.
Wide angle	Used for any lens that has an angle of view greater than the human eye – which is between 40 and 60 degrees. It is not possible to give a single angle of view for the eye as it depends on variable factors. With 35mm photography, wide angle starts at about 35mm focal length.
winder	a device to automatically wind on the film
X synch	This is a method of synchronising the firing of an electronic flash with the opening of the shutter. As an electronic flash does not need time to reach maximum brightness, the flash is fired as the shutter is fully open.
Zeiss bumps	Bumps on the outside of Zeiss Ikon cameras caused by the rivets used to hold components together chemically reacting with the body of the camera. This causes visible bumps under the leatherette covering.
zoom	a lens that has an adjustable focal length