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Photo Glossary - P

Painting with light - technique of lighting large, dark interior. The camera, mounted on a tripod, is given a long time exposure. The photographers moves continuously around the interior, giving flash or battery powered photoflood illumination to the shadow areas.

Pan and tilt head - tripod head allowing the camera to be tilted up and down or turned through a 360 arc.

Panchromatic - photographic emulsion sensitive to all the colors of the visible spectrum and to a certain amount of ultra-violet light. The sensitivity is not uniform throughout the spectrum.

Panchromatic vision filter - filter through which the subject can be viewed approximately as it would appear in monochrome as recorded by a panchromatic emulsion.

Panning - technique of photographing moving subjects. While the shutter is open, the camera is swung in the same direction as the subject is moving. This creates a blurred background, but a sharp subject.

Panorama - picture presenting a continuous view of the landscape, produced either by using a panoramic camera or from a composite of several images.

Panoramic camera - camera with a special type of scanning lens which rotates on its rear nodal point and produces an image of the scanned area on a curved plate or film.

Paper base - support for the emulsion used in printing papers.

Paper characteristic curve - describes a graphical relationship between exposure values and image density of a printing paper. Each brand of paper may have a different initial characteristic curve. The shape of the curve can be altered by different developers, development times, temperatures, and toning.

Paper grade - numerical and terminological description of paper contrast: numbers 0 - 1 soft; number 2 normal; number 3 hard; number 4 - 5 very hard; number 6 ultra hard. Similar grade number from different manufacturers do not have the same characteristics.

Paper safe - light-tight container for unexposed photographic papers, with an easy open positive closing lid.

Parabolic mirror - silvered glass or metal reflector with a parabolic axial cross-section, used to produce near parallel rays from a light source positioned at its geometrical focus.

Parallax - difference between the image seen by a viewing system and that recorded on film. Only TTL viewing systems avoid parallax error.

Paraphenylenediamine - reducing agent used in some fine grain and color developers.

Paraphotography - general term for non-silver-halide image forming processes.

Paraxial - rays nearest the optical axis of a lens.

Patch chart - squared pattern test strip often made when color printing by the additive method.

PCT - see Photo color transfer.

PEC - see Photo-electric cell.

Pellicle (pellicule) - thin film used in one-shot color cameras as a semi-reflecting surface.

Pentaprism - optical device, usually fitted on 35mm cameras, which makes it possible to view the image while focusing. A mirror device laterally reverses the image so that the scene is viewed through the camera upright and the right way round.

Percentage solution - solution containing a given quantity of a dissolved substance in a stated volume of solvent.

Perforations - accurately spaced holes punched throughout the length of film for still cameras. Basically the perforation function as a guide for precision registration of film and also provide mechanical movement from frame to frame.

Periphery photography - technique used to photograph the entire inner or outer surface of a cylinder or tube.

Permanence tests - methods of establishing whether long term permanence of an image has been achieved.

Perspective - relationship of size and shape of three-dimensional objects represented in two-dimensional space.

Petzval lens - early lens system developed by Joseph Petzval. It had a very wide aperture and was relatively free from aberration. Many modern lenses have developed from this simple three-element design.

Phenidone - reducing agent used in many fine grain solutions.

Phenol varnish - resin used to produce a hard durable top coating.

Phosphorescence - property held by some materials of absorbing light of one wavelength and emitting it as light of a different wavelength.

Phosphotophotography - technique of projecting an infrared image on a phosphorescent surface.

Photo color transfer - method of making color enlargements by exposing on full size sheet film which is then soaked in a activator solution and rolled in face contact with receiving paper. The sandwich is then left in normal light for 6-8 minutes and peeled apart to give a finished print.

Photo elasticity - method of determining stress patterns in structures with the aid of polarized light.

Photo-electric cell - light sensitive cell. Two types are used in exposure meters. A selenium cell generates electricity in proportion to the amount of light falling upon its surface. A cadmium sulfide cell offers a resistance to a small electric charge when light falls upon it. Cadmium sulfide cells are more sensitive then selenium, especially at low light levels.

Photo-engraving - production of a relief printing surface by chemical or mechanical means, with the aid of photography.

Photo-etching - technique of contact printing an image on lith film on a presensitized zinc plate which is then processed and chemically etched to give a relief image.

Photo file index print - makes ordering reprints and enlargements easy. A small print shows a positive, "thumbnail" version of every picture on an APS roll. Each thumbnail picture is numbered on the index print to match the frames inside the cassette.

Photoflood - artificial light source using a tungsten filament lamp and a dish reflector.

Photogenic drawing - original name given by William Fox Talbot to his earliest method of recording camera images.

Photogram - pattern or design produced by placing opaque or transparent objects on top of a sensitive emulsion, exposing it to light and then developing it.

Photogrammetry - method of making precise measurements from photographs.

Photography - literally writing or drawing with light (from the Greek words photos meaning light and graphos, writing). First suggested by Sir John Herschel to William Fox Talbot in 1839.

Photogravure - method of printing photographs from an etched copper plate.

Photolamp - tungsten filament photographic lamp with a large diffused bulb, giving light of 3200 K (kelvin).

Photolinen - laminate of linen and paper coated with black and white photographic emulsion. It is used for photographic wall coverings.

Photolithography - lithographic printing process using an image formed by photographic means.

Photometer - instrument for measuring light being reflected from a surface. It works by comparing the reflected light with a standard source produced within the photometer.

Photomicrography - system of producing larger than life photographs by attaching a camera to a microscope.

Photon - particle of light energy. It is the smallest quantity of radiant energy that can be transmitted between two systems.

Photo-reportage - use of photographs in newspapers and magazines, to supplement or replace written journalistic accounts.

Photo-resistor - photoelectric cell which varies in its electrical resistance according to the light received.

Photo-silkscreening - method of silkscreening images, using a stencil produced photographically.

Photo telegraphy - transmission of pictures between two points by means of radio or telegraph. A print is wrapped around a cylinder and scanned by a small spot of light. Reflected light values are transmitted as a stream of signals. They control an exposing light source at the receiving station, which exposes light sensitive material on a similar drum.

Photo-transistor - light sensitive electronic component which functions as a switch. Used for slave firing of electronic flash heads.

pH scale - numerical system running from 0-14 and used to express the alkalinity or acidity of a chemical solution. 7 is neutral. Solutions with a lower pH value are increasingly acidic, and those with a higher pH value are increasingly alkaline

Physical development - system of development in which silver is contained in suspension within the developer and is attracted to the emulsion by silver halides which have received exposure.

Physiogram - photographic patter produced by moving a regulated point of light over a sensitive emulsion.

Pictorialist - photographs which are a picturesque, decorative art in their own right and appeal to the viewers sense of beauty.

Piezo-electric flash - tiny flash bulbs (normally housed in flash cubes) which can be fired by a very low current produced by striking a piezo-electric crystal. Such bulbs can therefore be used without a battery.

Pigment - coloring material that is insoluble in the liquid carrier with which it is mixed. Examples include paint or poster color.

Pigment processes - making a positive print by using the property of bichromated colloids by changing their physical characteristics with exposed light. Gum bichromate is a pigmented process.

Pinacryptol - yellow and green dye powders which are used in desensitizing solutions.

Pincushion distortion - lens aberration causing parallel, straight lines at the edge of the image to curve toward the lens axis.

Pinhole camera - camera without a lens which uses a very small hole pierced in one end to allow light to pass through and form an image on the back of the camera which can be covered by film.

Pixels - abbreviation for picture elements. The tiny squares of light making up the picture are transmitted in digital form and reconstituted as a visual image.

Plane - imaginary straight line on which image points may lie or which passes at right angles through a set of points perpendicular to the optical axis.

Plates - early photographic glass plates coated with emulsion.

Plate camera - camera designed to take glass plates but often adapted to take cut film.

Platinotype - obsolete contact printing process popular among pictorialists.

Point source lamp - arc type lamp producing light from a small gap between two carbon rods.

Polarization - light said to travel in a a wave motion along a straight path, vibrating in all directions. Polarization can be brought about with a polarizing filter which causes light to vibrate in a single plane only. Polarizing filters are used over camera lenses and light sources to reduce or remove specular reflection from the surface of objects.

Polarized light - rays of light that have been restricted to vibrate in one plane only.

Polarizing filter - colorless gray filter made from stressed glass. Polarizing filters are used over light sources or camera lenses to reduce or remove specular reflection from certain types of surfaces.

Polaroid camera - an instant picture camera designed for Polaroid materials.

Pola-screen - another term for a polarizing filter.

Portrait lens - lenses produced specifically for portraiture. They usually have a long focal length and produce a slightly diffused image.

Positive - in photography, the production of prints or transparencies in which light and dark correspond to the tonal range of the original subject.

Positive lens - simple lens that causes light rays from a subject to converge to a point.

Positive/positive printing - process for printing a color transparency directly on paper to produce a positive print.

Posterization - photographic technique using a number of tone separated negatives which are printed on high contrast material. A master negative is made by printing these in register. The final print from this contains selected areas of flat tone in place of continuous tone. Sometimes incorrectly referred to as solarization.

Potassium bichromate - chemical used in chrome intensifiers.

Potassium bromide - chemical used as a restrainer in most developing solutions and as a rehalogenizing agent in bleaches.

Potassium carbonate - highly soluble alkaline accelerator used in most general purpose and print developing solutions.

Potassium chloride - chemical used in some bleaches and sensitizers.

Potassium citrate - chemical used in blue and green toners.

Potassium dichromate - See Potassium bichromate.

Potassium ferricyanide - chemical used in Farmer's reducer as a bleach.

Potassium hydroxide - caustic potash. Highly active alkali, used as the basis for high contrast developing solutions.

Potassium iodide - chemical used in bleaches, toners and intensifiers.

Potassium metabisulfite - acidifier used in fixers and stop baths.

Potassium permanganate - chemical used extensively in reducers, bleaches and toners.

Potassium persulfate - chemical sometimes used in super-proportional reducers.

Potassium sulfide - chemical used in sulfide toning.

Potassium thiocyanate - chemical used in some fine grain developers as a silver solvent.

Prehardener - chemical solution used to harden the gelatin of an emulsion prior to processing.

Preservative - chemical, commonly sodium sulfite, used in developing solutions to prevent rapid oxidation of the reducing agents in use.

Preset focus shooting - technique in which focus is set at a predetermined setting and the shutter is released when the subject moves into the focus point.

Pre-soak - preparatory water bath for film or paper prior to processing that prevents uneven development. It is essential in some color processes.

Press focus lever - lever found on the between-lens shutter of many large format cameras. It allows the shutter blades to be held open for lens focusing no matter what shutter speed has been set.

Primary colors - three primary additive colors of the spectrum in terms of transmitted light. These colors are blue, green and red.

Principal axis - imaginary line which passes through the center of curvature of all the lens elements.

Principal planes - imaginary lines which pass through the nodal planes of a lens system.

Principal point - point from which the focal length is measured. The principal point of a simple lens is located at the center of the lens. Compound lenses have two principal points, the location of which cannot be determined by appearance.

Print - in photography is an image, normally positive, which has been produced by the action of light on paper or similar material coated with a light sensitive emulsion.

Printing - process employed to make one or a number of images on paper or similar material.

Printing-in - system of local shading control used in printing in which additional exposure is given to selected areas of a print.

Printing-out papers - light sensitive printing papers which visibly darken during exposure to sunlight. Also referred to as contact printing papers.

Prism - transparent medium capable of bending light to varying degrees, depending on wavelength.

Processing - sequence of steps whereby a latent photographic image is converted into a visible, permanent image.

Process lens - lens system designed specifically for high quality copying.

Projection cutting - any method of printing in which the image is optically projected on the sensitized material.

Projector - apparatus used to display enlarged still or moving images on to a screen.

Proportional reducer - chemical method of reducing excess density and contrast from a photographic negative.

Protective toning - toning process used to protect black and white prints from fading and give archival permanence. Usually used selenium or gold toners.

Pulling - method of underrating the normal ISO speed of a film to produce an overexposed latent image.

Pushing - method of overrating the normal ISO speed of a film to produce an underexposed latent image. Used to increase the working speed of a film.

Push processing - increasing the development time of a film to increase its effective speed. See Pushing.

Pyro - reducing agent sometimes used in developing solutions.

Photo Glossary - Q

Quantum - smallest indivisible unit of radiant energy.

Quarterplate - negative or print format measuring 3 x 4 inches. It's one quarter the size of a full plate (8 x 6 inches).

Quartz-iodine lamp - compact tungsten filament lamp designed to maintain its color temperature and light intensity throughout its working life.

Photo Glossary - R

Rack and pinion focusing - mechanical focusing system used on copying or monorail cameras. A pinion engages a rack on a slide. Focusing is achieved by turning a knob or wheel, which moves the lens or image panel.

Radiography - technique of using X-rays, gamma rays and charged particles to form shadow images on photographic materials. Used in medical and industrial research because of its ability to penetrate opaque objects.

Rangefinder - focusing system which measures the distance from camera to subject.

Rapid fixer - fixing solution that uses ammonium thiocyanate or thiosulfate instead of hypo.

Rapid rectilinear - lens system composed of two matching doublet lenses, symmetrically placed around the focal aperture. It was introduced by Dallmeyer and Sternheil and removed many of the aberrations present in more simple constructions.

Rayographs - term coined by Man Ray and his friends for pictures made by placing directly on photographic paper (i.e. photograms).

Rear curtain sync - when the flash fires an instant before the second or rear curtain of the focal plane shutter begins to move. When slow shutter speeds are used, this feature can create a blur effect from the ambient light, i.e., patterns following a moving subject with subject movement frozen at the end.

Rear focus - refers to the focused area behind the picture's subject.

Rear focusing system - system where only the rear lens group moves during focusing. It eliminates changes in the physical length of the lens during focusing.

Rebate - margin on photographic film surrounding the image area.

Reciprocity failure - in photographic emulsions occurs when exposure times fall outside a films normal range. At these times an increase in exposure is required in addition to the assessed amount. This can be achieved either by increasing intensity or time.

Reciprocity law - states that exposure = intensity x time, where intensity is equal to the amount of light and time is equal to the time that amount of light is allowed to act upon the photographic emulsion.

Reconstituted image - photograph produced by translating light from the subject into electronic signals.

Recycling time - time it takes a flash unit to recharge between firings.

Red eye - effect encountered when light from a flash unit travels parallel to the lens axis during exposure.

Reducers - solutions which remove silver from negatives and prints. They are used to diminish density and alter contrast on a photographic emulsion.

Reducing agent - chemical in a developing solution which converts exposed silver halides to black metallic silver.

Reflected light - light bounced off a subject, not falling on it.

Reflected light reading - measurement by a light meter of the amount of reflected light being bounced of the subject. The light meter is pointed towards the subject.

Reflecting telescope - telescope using a concave parabolic mirror to increase focal length and focus light at a point.

Reflections - rays of light which strike a surface and bounce back again. Specular reflection occurs on even, polished surfaces; diffuse reflection occurs on uneven surfaces, when light scatters.

Reflector - any substance from which light can be reflected. It also describes a white or gray card used to reflect from a main light source into shadow areas.

Reflex camera - camera system which uses a mirror to reflect incoming image rays on to a ground glass screen, providing a system of viewing and focusing. See also SLR.

Reflex lens - alternative term for mirror lens.

Refraction - change in direction of light rays as they pass obliquely from one transparent medium to another of different density, e.g. air to glass.

Refractive index - numerical value indicating the light bending power of a medium such as glass. The greater the bending power, the greater the refractive index.

Register - exact alignment when overlaying separate images.

Register punch - punched used to make alignment holes in film or paper for registering images.

Rehalogenization - process by which black metallic silver is converted back to silver halides. It is used in bleaching for toners and intensification.

Relative aperture - measurable diameter of the diaphragm divided by the focal length of the lens in use and expressed in terms of "f" numbers, marked on the lens barrel.

Replenishment - addition of chemicals to a processing solution to maintain its characteristics, e.g. developers are replenished with reducing agents as the old ones are exhausted through use.

Resin coated paper (RC) - printing paper with a water repellent base. RC Paper can be processed faster, require less washing, and dry more quickly than fiber based papers.

Resist - protective but removable layer applied to a surface in the form of a pattern or image. Used to prevent chemicals solutions reaching covered areas.

Resolving power - ability of the eye, lens or photographic emulsion to determine fine detail. In photography, the quality of the final image is a result of the resolving power of both the lens and the sensitive emulsion. Resolution is expressed in terms of lines per millimeter which are distinctly recorded or visually separable in the final image.

Restrainer - chemical constituent of developing solutions which helps prevent reducing agents from affecting unexposed halides and converting them to black metallic silver.

Reticulation - regular crazed pattern created on the emulsion surface of negatives which is caused by extreme changes of temperature or acidity/alkalinity during processing.

Retrofocus - type of lens design with a negative lens element positioned in front of the diaphragm and a positive lens element positioned at the rear of the diaphragm. This makes the distance from the rear of the lens to the focal plane longer than the lens focal length. Retrofocus design has been adopted in wide angle lenses so the rear of the lens does not impede the movement of an SLR camera's reflex mirror.

Retouching - after treatment carried out on a negative or print, in the form of local chemical reduction, local dye or pencil additions or air-brushing. The purpose is to remove blemishes on the negative or print.

Reversal materials - materials specifically designed to be processed to a positive after one camera exposure.

Ring flash - ring shaped electronic flash unit attached to the front of a lens. Used to give even frontal lighting in closeup situations.

Rinse - brief clean water wash between steps of a processing cycle to reduce carry-over of one solution into another.

Rising front - camera movement enabling the front lens panel to be raised or lowered from its central position on most view cameras.

Rods - receptors forming part of the retina at the back of the eye sensitive only to variations in brightness, not color.

Roll film - refers to 120, 220 and 620 film formats.

Roll film adaptor - specially designed attachment for cameras designed for cut film, enabling roll film to be used.


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