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.
Parallax The differences between the positions of objects when you move your viewpoint. Noticeable when using a viewfinder that is offset from the lens.
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.
Relative aperture This is also known as the ƒ/number (which see). It is the focal length of the lens divided by the physical aperture
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.
Selenium meter This is a type of light meter that used selenium as its sensor. Selenium produces a small voltage when exposed to light and the meter reads this voltage to determine the light intensity. The advantage of using selenium is that no battery is required. The main disadvantage is that they do not work in low light.
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 curtain In early focal plane shutters (until the 1970s) a pair of cloth blinds that have been rubberised to be light-proof. One opens to expose the film and then the other closes to stop the exposure. Actually, they work by forming a moving slit which allows for very fast shutter speeds. From the 1970s, the cloth blinds were replaced by metal slats (from 1932 with the Zeiss Ikon Contax)
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.
Spotmeter A light meter that only measures the light coming from a small spot rather than the general area. An option with TTL meters and can also be bought as a hand-held meter.
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.
Stop This is taken to be one unit of exposure although it is not officially defined. If you increase the exposure by one ‘stop’ you double the exposure and if you reduce the exposure by one ‘stop’ you halve the exposure.
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.
T This is a shutter speed setting where the shutter opens when the shutter release button is pressed and then remains open until the shutter release button is pressed a second time. Like B, it is used for timed exposures but for longer than several seconds.
T-number This is similar to a F-Number Or F/-stop but gives the actual amount of light passed by the lens. It is mostly used in cinematography to ensure each frame is exposed exactly the same as others. You can convert from an F-Number to a T-Number by the formula: T=F/√(transmittance)
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 inch or ¼ inch 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.
UNC This is a formal standard for engineering screw threads. It is the current standard for tripod threads. It is compatible with the older standard of Whitworth threads for hand-adjusted screws.
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.
Whitworth This is an obsolete standard for engineering screw threads. It was the standard for tripod threads from Victorian times up to ISO defining the thread to be used for tripods (UNC). Modern and old tripod threads are compatible with each other.
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


Author: John Margetts

I am a keen photographer who also collects cameras. I am retired with about 50 years photography experience.

8 thoughts on “Glossary of Photographic Terms (O to Z)”

Leave a Reply to Exakta RTL1000 – John's Cameras Cancel reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: