Understanding Photographic Terms, Materials & Processes
GLOSSARY OF TERMS FROM THE BOOK. [Link ]
acid: a substance, usually in solution with water, that has a pH lower than 7.0. Acids have a corrosive effect on metals and are commonly used as etches in the printing trades.
additive color: see primary colors
albumen (also albumin): a soluble protein commonly found in egg white.
albumen print: a silver photographic printing-out process that was developed to render the long range of tones held in wet-plate glass negatives. The albumen print is a refinement of the earlier salted-paper print, but it differs in using a heavy coating of albumen as a binder for the salt and subsequent silver image. Albumen prints have a long tonal range and strong blacks, and they were almost always toned with gold, producing a purplish image.
ambrotype: a lightly exposed wet-plate glass negative that appears as a positive when placed on a black backing.
analog: a representation of something that imitates a physical characteristic of the original. The photographic negative is an analog, in silver, of the variable light intensity striking the film during exposure.
aquatint: a randomly distributed array of grains of an acid-resistant material, applied to an intaglio printing plate before etching to protect parts of the surface from the etch. The pattern of the grains confines the etching to small cells between them. Those areas not etched act as a wiping guide for the cloth or hand that cleans the inked plate. Ink remains in the cells and is transferred to the paper in the press.
architectural plotter: a large-format inkjet printer designed to generate architectural drawings.
asphaltum: a hardened asphalt that can be used as an etching resist, whether dissolved in turpentine or in powdered form.
autochrome: see Lumière Autochrome
autopositive: any photographic process that produces a positive image directly from exposure to light. In most photographic processes, light darkens a photosensitive material in such a way that the brightest light produces the darkest areas of the picture, resulting in a negative image that must then be printed to make a positive. Autopositive processes, such as the daguerreotype, tintype, and ambrotype, produce a positive directly with no intermediate negative stage.
bar code: a printed pattern of lines, readable by an optical scanner, used to automate product logistics. Bar codes allow manufacturers and retailers to create automated inventories and are used to direct objects during shipping.
binary: for printing purposes, “binary” refers to a description of information with only two possibilities: at a given point on a white sheet of paper, for example, black ink is either present or not—there are no intermediate tones. The common halftone, which prints small dots in varying sizes, is a method for generating the appearance of such intermediate tones with only black ink and plain paper. Computers use a binary mathematical system in which 1 and 0 are the only numerals, as these can be efficiently represented by an electronic switch that is either on or off.
black and white photography: photography that renders all colors in monochromatic values. Black and white prints have no color information deriving from the scene photographed, but they often have color casts derived from the particular chemical process used to produce them.
blueprint (also cyanotype): an iron-based photographic printing process using inexpensive iron compounds and simple development in water. Used predominantly for engineering drawings, the process was also widely used as an amateur photographic printing medium.
burin (also graver): a specialized cutting tool, acting more like a gouge than a knife, that is used to engrave lines in metal or wood. Driven by the palm of the hand and guided by the fingers, the burin is held nearly flat to the surface that is to be engraved. Its slanted, usually lozenge-shaped point cuts a groove that varies in depth according to the angle at which the burin is held above the surface.
burnisher: a hand tool used to polish mezzotint plates and to do corrective work on etchings, engravings, and even photogravures. Burnishers have highly polished tips made of steel or agate mounted in a wooden handle.
C-print: see chromogenic process
calotype (also talbotype): the first negative-positive photographic process, invented and named by William Henry Fox Talbot. Salted-paper is used for both negatives and positives.
camera: a light-tight box holding some form of light-sensitive recorder (film or digital sensor), with an image-forming aperture (lens or pinhole) and a means of admitting light for a controllable interval.
carbon black (also lampblack): this amorphous form of carbon results from a gas flame burning without sufficient oxygen. Carbon black was the original pigment for carbon printing and gave the process its name.
carbon print: a photographic process based on the tendency of a colloid (in this case gelatin) to harden upon exposure to light when previously treated with a bichromate. Carbon prints are made using a sheet of paper called “carbon tissue” that has been coated with gelatin into which pigment has been mixed. After exposure, the gelatin-coated sheet, hardened according to the degree of exposure from the different tonal densities of the negative, is processed to wash away the unhardened gelatin along with the pigment it contains, leaving a print made of the remaining pigmented gelatin. During processing the exposed gelatin must be transferred to a new support. Sometimes this is to be done twice: the transfer to the first support reverses the image, so that it must be transferred from that sheet to a second one to read correctly.
carbro print: a variation of the color carbon print, in which the pigment-bearing gelatin is hardened by contact with a bleached silver-based color separation instead of by direct exposure.
carte de visite: a small photographic portrait, approximately 2¼ by 3½ inches (6 x 9 cm), that was mounted on a card similar in size to a calling card. These small pictures were very common in the second half of the nineteenth century and were usually made by the albumen process.
chromogenic process: a photographic color process that uses three silver images on a single support to create corresponding dye images in the subtractive primary colors. The three superimposed dye images yield a full-color image. Both films and prints are produced using this process. Eastman Kodak’s Kodachrome transparencies and Kodacolor prints use the chromogenic process, as do similarly named materials produced by other companies, such as Fujichrome and Fujicolor.
chromolithography: color printing using multiple lithographic stones to produce prints with a wide range of colors. The most complex chromolithographs involve many stones, each printed in its own color. Tonal variations are produced by superimposed patterns of stippled dots.
Cibachrome: an autopositive photographic color print process, renamed Ilfochrome after Ilford bought Ciba-Geigy.
CMYK: color printing using cyan, magenta, yellow, and black, the first three being the subtractive primary colors. (“K” is used to designate black to avoid confusion, since “B” might represent blue.) Ideal subtractive printing would not require black, since the three primaries together should produce it, but practical considerations of press and paper require this fourth ink. CMYK is also used as a file type in the computer, when a four-channel file emulates the colors of the subtractive primaries.
collodion: a solution of nitrocellulose in ether.
collodion wet-plate: see wet-plate process
colloid: a general term, not in much favor with chemists today, used to group natural glues and jellies such as fish glue and gelatin.
collotype: a lithographic printing process that uses a reticulated gelatin coating on a glass plate as the printing surface. Collotype plates are exposed from continuous-tone negatives without the need for a halftone screen.
color balance: color photographs can vary greatly in hue, but when the gray values in such pictures are neutral we say the color balance is correct. Color balance is greatly affected by the hue of the light used to make the picture.
color carbon print: a carbon print made by superimposing three carbon prints in register, each in a subtractive primary color, exposed from the appropriate color separation.
color management: the practice of controlling color in a wide range of digital processes. Color management is complex and unwieldy, and is based on the premise that color errors in any given stage of a process can be codified and controlled, and that if this is done for all steps in an extended process, then the color rendering can be accurate. The mechanism on which color management is based is the color profile, which handles the specific color rendition of each device and manipulation.
color mixing: in traditional mediums such as painting, colors are mixed in a loosely defined manner, and in grade school we were taught that yellow and blue mixed together made green. In modern photography and printing, colors mix in a carefully defined manner. Pure cyan and magenta pigments or dyes, when mixed together, produce blue. Yellow and cyan combine to produce green while yellow and magenta produce red. When light is mixed (as in the computer monitor), blue and green produce cyan, blue and red produce magenta, and red and green produce yellow. Varying amounts of any color produce shades of varying saturation and lightness.
color profile: a color table that describes the accuracy and errors of a digital color-handling process. A profile is attached to any file that carries color information and forms a chain of control that runs through the entire process. Cameras, scanners, printers, and computer monitors all have profiles, and these work together (in theory) to allow the proper control of color. See color management.
color saturation: a measure of the purity of a color—the degree to which it is free of dilution by white or gray. As a pure color becomes lighter it is diluted by white; when it becomes darker it is diluted by gray; and in either case it becomes less saturated. In both subtractive and additive color, saturation is reduced when more than two primaries are mixed. In the subtractive system the third primary produces grayness; in the additive system the third primary produces lightness. In strictest terms, the only fully saturated colors are full-strength examples of a single primary or a combined pair.
color separation: the process of photographing an original through filters to produce three black-and-white images, each of which records a portion of the color spectrum. Red, green, and blue filters respectively produce the color records for cyan, magenta, and yellow. These separations, after subsequent adjustment, are printed in register with each other and in the appropriate primary colors, producing subtractive prints that carry a wide range of colors.
complementary colors: colors complement each other when they are opposed across the additive and subtractive systems. Thus blue complements yellow, since the increase of one is accompanied by the reduction of the other. The same is true of red and cyan and of green and magenta. See primary colors.
contact paper: an obsolete type of photographic developing-out paper with a moderate light-sensitivity that made it suitable for printing by contact. These papers used silver chloride as the dominant sensitive chemical, and while much “slower” (less sensitive) than enlarging papers, they were much “faster” than the older printing-out papers such as albumen paper.
contact print: a print that has been exposed by placing the negative in direct physical contact with the print material (as opposed to enlargement, when the image passes from negative to print material through a lens system).
contrast: a loosely used photographic term referring to the degree of separation between a picture’s lightest and darkest tones. A high-contrast print might have bright light values and dark shadows while a lower-contrast image would be grayer at both ends of the tonal scale.
copper engraving: an intaglio process using copper plates cut with a burin. Many so-called engravings were made with some amount of etching, marking the copper not with a burin but with an acid or other solvent. Etching was often used to begin a plate that was then cleaned up with a burin.
cross-hatching: in linear processes such as engraving, the practice of describing tone by closely spacing black lines on a white ground. Cross-hatched groups of lines often run at right angles to each other, forming a linear grid that appears to the eye as tone when viewed from a sufficient distance.
cyanotype: see blueprint
daguerreotype: one of the first practical photographic processes, publicly announced in 1839 and named for the French artist/inventor Louis Jacques Mandé Daguerre. A light-sensitive coating on a silver-plated copper sheet produced brilliant and sharp images, which, when sealed under glass, have proven to be extremely permanent. Since daguerreotypes are autopositive, each one is unique.
dauber: a soft, rounded, cloth-covered tool held in the hand and used to apply color when stenciling.
developing-out paper (DOP): the modern class of black-andwhite papers that register a latent image and so need to be developed after exposure to produce a visible image. This term is commonly used to refer to modern gelatin silver papers, which are most often made extremely sensitive so that they can be used in enlargers.
digital: in printing and photography this term refers to image data made up of discrete points that are assigned numerical values in order to hold a record of visual information. Digital processes are radically different from the older analog systems, such as film, which record data through continuous material variations.
digital C-print: a chromogenic print that has been exposed by lasers driven from a digital file instead of being exposed in a conventional enlarger.
dry plate: a gelatin-and-silver-based photographic negative material, invented in the late nineteenth century, that could be factory produced, packaged, and sold at a later date. The dry-plate coating has existed in many variations and has been used on both glass plates and flexible film. When coated on paper, it became the basis of most developing-out papers of the twentieth century.
drypoint: work done on an etching plate with a needle, to raise a burr that will catch ink and print without the need of chemical etching. Drypoint is often done as afterwork on etched plates. Work done this way is delicate and cannot withstand long-edition printing.
duotone: an ink printing method in which two superimposed halftone images of a single picture are printed with different inks, to render tone more accurately than is possible with a single impression.
dusting box: a large box, sometimes suspended in bearings so that it can be turned, used to apply a random aquatint to a printing plate. The material inside is usually powdered asphaltum, which is stirred up in the box and then allowed to settle on the plate surface.
dye: a soluble compound or liquid that reflects or absorbs a specific color. Dyes tend to be less stable, or lightfast, than pigments.
dye sublimation print: a digital process that transfers dye images to a receiver sheet through the use of heat. Small heating elements, as small as 200 per linear inch, are heated to varying degrees to affect correspondingly small, correspondingly varying amounts of dye. Dye sublimation prints are usually made in color, using the three subtractive primaries and black.
dye transfer print: a chemical photographic printing process (as opposed to a digital one) that created a full-color print by the use of three color separations, each controlling a layer of dye.
emulsion: a mixture of an insoluble solid or liquid suspended in another liquid. The most common emulsion in photography is the suspension of silver salts in gelatin, used for photographic films and papers.
end grain: the grain in a wooden block that has been cut perpendicularly to the growth of the wood. The cells in wood are long and narrow, running parallel to the trunk or branch of a tree. An end-grain surface presents these cells cut across their thin dimension. Because of their density, end-grain blocks can hold extremely fine carving, and when made of a hard wood they can be used in a form with metal type. See also side grain.
engraving: the process of removing material from a printing surface (usually metal or wood) through the use of a burin. Engraved lines in an intaglio process hold ink, and print; in a relief process they create nonprinting areas.
enlarger: a specialized camera used in the darkroom to expose photographic paper from a negative. Consisting of a light source, negative stage, bellows, lens, and stand, the enlarger projects the negative image onto light-sensitive paper, which is subsequently developed to produce the positive image. Because the artificial light of the enlarger is much weaker than the sun, enlargements must be made on highly sensitive developing-out papers. An enlarger allows prints to be made bigger than the negative, although same-size or even reduced-size enlargements are also possible.
etching: most commonly, an intaglio printing method in which the ink-bearing cells or lines of an image are formed by chemical action on a printing plate. In plate-making, etching is the removal of metal through chemical action, by an acid or some other solvent. In lithography, etching is the treatment of the printing surface to produce a chemical distinction between printing and nonprinting areas.
etching needle: the etcher’s primary drafting tool, usually made of steel with a sharp point. The etching needle, which is held like a pen, can draw lines through a resist before etching or can generate actual printing lines when applied with more pressure. See drypoint.
etching press: a press using two heavy cylinders and a solid steel bed that runs between them. Properly called a “mangle,” the press can apply the tremendous pressure needed to squeeze the paper and plate sufficiently to transfer the ink from the plate recesses onto the damp paper of the print. Usually hand driven, these presses are used for printing engravings, etchings, mezzotints, and flat-plate photogravures.
ferric chloride: a watery, acidic iron solution that can swell hard gelatin, pass through it, and dissolve copper. Ferric chloride is the etch used in photogravure.
ferrotype tin: a high-gloss polished sheet, usually of chromed steel, that can be used to dry photographic paper so that it takes on a high sheen.
film format: a loosely used term that refers to both the size and the shape of camera negatives. The 35mm format is also called two-by-three, reflecting its proportions, and the four-by-five- and eight-by-ten-inch formats are the same shape but differ in size. Both the English and the metric systems are used for film formats, so six-by-nine is the same shape as 35mm but is six by nine centimeters in size, on what Americans call 2½-inch roll film.
fixer: see hypo.
foxing: a discoloration often appearing on old prints, typically in patterns of rust-colored dots.
gelatin: a transparent protein produced from animal tissues, gelatin is the coating used in most photographic emulsions. When wet, it swells in a controllable fashion, allowing the management of the chemical reactions within the emulsion.
gelatin printing-out paper (also gelatin POP): a late variant of the albumen print in which gelatin replaced albumen.
gelatin silver paper: the modern designation for the common black and white developing-out photographic paper used for much of the twentieth century.
giclée print: an ordinary inkjet print, so called to enhance its salability.
gouge: a chisel with a concave blade, used for making woodcuts.
graflex camera: an early single-lens reflex camera that used sheet film, generally four by five inches but as large as five by seven inches.
gravure: an intaglio process in which a photographic image is etched in a copper support. The image is broken up into inkbearing cells that vary in depth and consequently hold different amounts of ink, allowing the printed image to carry true tonality. Gravure comes in many forms; the name has become the generic term for a whole family of intaglio photographic printing processes, and the naming of these variations is nearly endless. We find the terms “gravure,” “photogravure,” “hand gravure,” “aquatint gravure,” “flat-plate gravure,” and “heliogravure” (among others) all used for the same process: hand-wiped gravure prints of photographs made from flat plates. When gravure is mechanized, becoming a rotary process, it is referred to as “gravure,” “photogravure,” “rotogravure,” and just plain “roto” (among others). In Europe the term “gravure” is used to mean an intaglio print, either an engraving or an etching.
gum bichromate: a pigment process using gum Arabic mixed with pigment to produce a photographic image. Usually applied to rough watercolor paper, this process was a favorite of the Pictorial photographers of the early twentieth century.
halftone: a printed image in which the continuous tones of a photograph have been converted into a regular grid of highcontrast dots of variable size. In the past, halftone negatives were produced by photographing an original work through a screen. Modern digital technologies create halftone dots directly, from smaller dots made by computer-run lasers. A halftone negative can be used to create relief, intaglio, or planographic printing plates.
halftone screen: originally a glass screen with ruled black lines in a pattern similar to a window screen. When used with the correct high-contrast film and developer, the screen would break continuous tone into dots of varying size. In the 1950s the glass screen was replaced with a film replica, which in turn has now been replaced with screen patterns generated by computer software.
hand gravure: see gravure
hypo (also fixer): the generic term for the solution that fixes, or stabilizes, a chemically printed photograph by removing undeveloped silver compounds from a developed photographic emulsion. The two chemicals used almost exclusively as fixers are sodium thiosulfate and ammonium thiosulfate.
imagesetter: an electronic device designed to record digital image files on film. The result—an electronically generated halftone on film stock—could be used to expose photo offset lithographic plates. Imagesetters are now disappearing, since today most printing plates are exposed directly from digital files.
impression: the printer’s term for a single act of printing. Thus a print in more than one color, and so made from more than one plate, is called a “multiple impression” or “multipass.” Also used to designate the quality of ink transfer, so we may have a heavy or light impression, a rough or smooth one.
Indigo printer: an offset printing press that uses an electronic plate and polymer inks. By changing the digital file used to expose the plate, each impression can be made to vary from the one before. This means that an Indigo printer can print the pages of a book sequentially, so that a single copy can be produced at a reasonable cost.
ink: a marking fluid holding a dye or pigment. Most printing inks use oil as the body fluid, while writing inks often use water. There is no easily definable difference between ink and paint—both are applied to a surface to change its color—but they vary widely in the specifics of their makeup and their methods of application.
inkjet print: a print made by a digitally run machine that distributes small droplets of ink over a surface to create an image. In the overwhelming majority of these machines, a print head holding ink jets moves rapidly across a sheet of paper to apply stochastic patterns of ink in the subtractive primary colors. Early inkjet printers such as the Iris printer used a slow-moving set of jets that applied ink to a rapidly rotating sheet mounted on a cylinder.
intaglio: a process using a plate whose low portions carry the ink. The most common intaglio processes are copper and steel engraving, etching, and photogravure.
internegative: a copy negative used to make a new positive image.
Iris print: see inkjet print
justification: the practice of spacing letters and words so that columns of type (or hand lettering) are even on both sides. Unjustified columns tend to be even on the left and “ragged” on the right.
lantern slide: a 3¼-by-4-inch glass-plate positive made for projection. Lantern slides were most often used for educational purposes; they never enjoyed the broad popularity of 35mm slides in two-by-two-inch mounts, which succeeded them and which in turn have been replaced by modern digital snapshots.
laser print: a pattern of toner on paper, fixed by heat. The laser print resembles the Xerox copy but is generated from a digital file instead of an analog light image.
latent image: an invisible image produced by changes in lightsensitive silver emulsions. Chemical development makes the latent image visible.
lens: a transparent object, typically made of glass, whose polished curved surfaces converge or diverge light. Camera lenses are usually complex, consisting of individual lenses, a mounting barrel, and a diaphragm.
letterpress: relief printing from metal type and image-bearing halftone cuts in copper or zinc. Also the actual press used for relief printing.
linear: used to describe the response or behavior of some physical process that varies consistently according to the action generating it. Film has a linear response to light in the mid-tones of a properly exposed negative. Many digital process are not linear, and require complex adjustments to be useful for picture-making purposes.
Linotype: a keyboard-driven machine manufactured by the Mergenthaler company to set metal type in rows cast in single lines. Invented in the late nineteenth century, it dominated typesetting for the first half of the twentieth century.
lithography: a planographic printing process that uses variations in the chemical nature of a treated stone (or of a coating on metal or plastic) to define which areas of the surface will and will not carry ink. The most common forms of lithography use a water film in the nonprinting areas and an oil-based ink in the printing areas.
Lumière Autochrome: one of the earliest color photographic processes, which produced autopositive color transparencies on a glass support.
makeready: the preliminary work to prepare a printing press for a production run.
matrix film: a specialized film manufactured by the Eastman Kodak company for use in dye transfer printing. The film was exposed, then washed in processing to produce an image in relief. The varying thickness of this matrix held varying amounts of dye.
metamerism: some inks’ characteristic of appearing to the eye as different colors when viewed under different light sources. Metamerism has been a severe problem in digital printing, and only the newest generations of inkjet inks are free from it. Metamerism usually leads to an image shifting toward red under yellowish light and toward green under cooler light such as daylight.
mezzotint: an intaglio process that uses a prepared copper plate roughened with a special tool called a rocker. This textured surface holds ink to print an overall black impression, and is selectively polished to produce lighter tones in chosen areas.
moiré (or moiré pattern): an interference pattern that can occur when two or more regular patterns are superimposed. Moirés are a common problem in color printing, but can be minimized by careful adjustments to the angles of the printing screens.
monotype: a print made from a plate that itself holds no printing information but carries ink manipulated to create an image. Also a form of machine-made lead type in which individual letters are cast and set according to information transmitted by a keyboard and perforated tape.
negative: the photographic record exposed in the camera, so called because it renders light values as dark and vice versa. Negatives have ranged widely in the materials of their support, from paper to glass to flexible film. Today they are disappearing, for they have no place in digital photography.
neutrality: a characteristic of tones that have no discernible color cast. On the computer screen, images in the RGB color system are perfectly neutral when the digital counts in the three color channels are identical.
offset blanket: in offset lithography, the blanket of rubber-faced cloth that wraps around the press’s middle cylinder and perfectly transfers the image from plate to paper.
offset lithography: see photo offset lithography
orthochromatic: lacking sensitivity to red light. Almost all early photographic emulsions were orthochromatic, and modern panchromatic materials (sensitive to all colors) were not common until early in the twentieth century.
palladium print: a variant of platinum printing in which the image is formed of metallic palladium instead of platinum.
panchromatic: see orthochromatic
pantograph: a device used to copy two- and three-dimensional structures, usually at a different size. The pantograph is an arrangement of linked parallel bars; the user traces the original with one part of the device, and a stylus or other marking tool moving in tandem with the tracing produces an enlarged or reduced version of the same structure.
photo offset lithography: a printing process whose presses use three cylinders: one carrying a thin metal plate, which holds the image; one the blanket, which picks up the ink image from the plate; and one the paper, to which the blanket transfers the ink. Photo offset lithography has been the most common printing process since the 1970s. All modern production offset presses are fully rotary and have two sets of rollers running on the printing plate, one for ink and one for water. They achieve very high speeds—upward of 12,000 revolutions per hour—and are built in serial units so that four, five, or even six or more colors can be printed on a single pass through the press. They are also very versatile: the use of the blanket allows accurate printing on many different surfaces.
photoglyptic engraving: a term used for some of the earliest efforts to make photographically derived printing plates. These methods were the precursors to photogravure.
photograph: a picture formed by the action of light on a chemical or electronic sensor, and subsequently fixed.
photogravure: see gravure
pigment: an insoluble compound that reflects or absorbs a particular color. Pigments are often ground into a fine powder to be used in paint or ink.
pixel: the point in a digital image for which the digital values have been recorded. Such images consist of an array of pixels; each one is dimensionless, and the more there are to a given area, the finer the image’s resolution.
planographic print: a print made by any process that prints from an even surface, using neither relief nor intaglio. In most planographic printing the printing and nonprinting areas are defined by chemical differences; these processes are grouped under the general term “lithography.” See also monotype.
plate tone: smooth and often quite light areas of tone left on an intaglio printing plate through incomplete wiping.
platinum print: a photographic print made using the light sensitivity of an iron compound (ferric oxalate) to create an image in metallic platinum. Many platinum prints also incorporate some percentage of palladium.
pochoir: hand coloring with stencils.
Polaroid: a chemical photographic process, manufactured by Polaroid Corporation in many variations, that produced autopositive prints soon after exposure without the need for darkroom processing.
positive: the opposite of negative; widely and loosely used in photographic parlance because the negative was typically the first step in the making of a chemical photograph. The term most often denotes a print but can refer to any tonally reversed image made from a negative.
potassium bichromate: a chemical used to sensitize gelatin and other colloids so that they become insoluble when exposed to light.
prepress: general term for all the preliminary work done before a job is actually printed. Before the onset of digital tools, prepress for offset printing consisted of making the film for reproductions and type, generating proofs, assembling the film into large flats that fitted the printing plates, and making the plates themselves by exposure through these flats. Today almost all prepress is electronic, carried out on the computer, and only comes to solid form with the making of proofs and the exposure of the plates.
primary colors: two different sets of primary colors are in common use. The additive set, used in projected-light devices such as computer monitors and television screens, comprises red, green, and blue. The subtractive set, used in reflective-light processes such as photographic printing and ink printing, consists of cyan, magenta, and yellow. The two systems are complements of each other. Painters historically used a different set of primary colors, considering red, blue, and yellow the primaries because they derived from individual pigments rather than from mixed colors.
printing: the production of an image, usually in ink, through the means of some matrix that holds the pictorial information in a reusable form. Prints can exist in single or multiple copies, but in all cases they entail the transfer of information from one physical structure to another.
printing-out paper (also POP): any photographic paper that generates a visible image directly from exposure to light, without development.
printing plate: for centuries, words were printed by arrays of metal type locked into printing forms. Pictures instead required a plate or block to carry the image. Different processes use a wide variety of materials for the plates.
process color: the professional term for full-color printing in ink using the three subtractive primaries—cyan, magenta, and yellow—plus black.
profile: see color management. An alternate name for the silhouette.
progressives: trial sheets made by a printer to aid in assessing proofs, usual in color printing and in complex black and white jobs. Four sheets, each printed in one of the four inks of process color that combine to make the corresponding plate, constitute a “set” of “singles.” When the set includes additional sheets that show combinations of two or more colors, it is called a “progressive” set.
proof: a preliminary test print, made to evaluate content for text or print quality for pictures. In some cases the proof is made on the same press to be used in the production run. More often it is a chemical or other surrogate for ink on paper, to avoid the high cost of makeready and press time.
red ocher: a naturally occurring iron oxide used as a pigment.
registration: the process of aligning sequentially printed superimposed images to fit each other.
relief print: a print made by any ink printing process in which the high parts of the printing surface take ink and transfer it to the print support. The most common relief processes are woodcut, wood engraving, letterpress (from metal type or halftone cuts), and linoleum cut.
resin-coated paper: photographic paper in which the paper base is sealed within a synthetic coating so that it does not get wet during processing. As a result the paper can be developed, washed, and dried rapidly.
resist: in etching, the waxy coating applied to a copper plate, through which the artist draws with a needle before the application of the etch. In photogravure, the gelatin carbon print applied to a copper plate, through which ferric chloride is applied as the etch.
reticulation: a wormy random pattern created in a gelatin coating by extremes of temperature. It is commonly regarded as a severe fault in improperly developed film. Collotype printing exploits controlled reticulation to produce a printing matrix.
RGB: red, green, and blue, the primary colors used in additive processes, such as computer and television displays.
RIP (raster image processor): a digital device, either hardware or software, that processes an image to generate the file that drives the printer. RIPs often come with profiles to control the quality of the printing.
rotogravure: see gravure
salted-paper: the earliest paper-based photographic material. So named because it was made by coating water containing a soluble salt onto a sheet of paper, which was subsequently coated with silver nitrate to produce a uniform coating of a light-sensitive silver compound.
saturation: see color saturation
scanner: any data-gathering system that employs sequential actions over time. In digital usage the term refers to a device that transfers analog picture information into a set of numerical values. The three most common forms of scanner are hand-held, flatbed, and drum.
scraper press: a lithographic press that applies pressure on the paper and printing stone with a stiff leather or plastic blade. The tremendous pressure that a cylinder can apply could easily break a litho stone. The scraper blade avoids this by being stiff enough to print, applying all its pressure on the leading edge, while being flexible enough not to damage the stone.
selenium toning: the practice of applying selenium compounds to silver photographic prints to alter their color or enhance their permanence. Unlike sepia toning, selenium is capable of very slight tonal changes, often barely intensifying the blacks.
sepia toning: the practice of applying sulfur compounds to a silver photographic print, typically to produce brownish tones.
serigraph: a commercial marketing term for the silkscreen print.
sheet-fed press: the most common printing press, which prints on individual sheets of paper instead of on the continuous rolls used in web presses. Sheet-fed presses range widely in size but are limited in speed by the mechanical demands of handling the individual sheets.
side grain: the grain in a wooden block that has been cut in parallel to the growth of the wood. Side-grain blocks can be large and were traditionally favored for woodcuts, while end-grain blocks, smaller but denser and more durable, were preferred for engraving. See also end grain.
signature: a single printed sheet of paper folded to make the pages of a book.
silk screen print: a stencil process employing a finely woven fabric stretched in a frame. The fabric allows ink to pass through areas not covered by the stencil, which can be made by hand or produced photographically. Silk screen printing can produce heavy, opaque layers of color, and fairly fine detail if the fabric is closely woven enough.
silver halides: the family of silver compounds, among them silver chloride, silver bromide, and silver iodide, that are highly sensitive to light.
silver print: a generic term for all photographic print processes based on the light sensitivity of silver salts. Most commonly, the modern gelatin silver developing-out print.
spot color: a particular color, specially mixed as an ink and printed from its own plate to enhance process-color printing.
steel engraving: an intaglio process, using plates of soft steel cut either with a burin (often driven by hand with a hammer) or by chemical etching.
stencil: a printing process that holds the pictorial information in a pattern of holes through which ink is passed to create a print. Stencils can be simple and coarse, such as those used to stencil shipping cases, or fine and precise, such as those used in silk screen printing.
stereo: a term with two distinctly different meanings. In printing, a casting of type and/or halftone images, producing a plate that can be mounted on a cylinder for high-speed printing (also called “stereotype”). In photography, a pair of photographs made with a camera designed with two lenses, to mimic human eyesight. When viewed through a specialized viewer, or by crossing one’s eyes, the images merge into an illusion of three-dimensional vision (also “stereograph”).
stippling: a pattern of closely arrayed dots that emulate tone. In intaglio printing the dots are typically cut by hand; in chromolithography they are made with a fine lithographic crayon.
stochastic: in printing, an apparently random pattern of dots used in lieu of the conventional halftone-screen array.
stripping: in offset printing, the process of splicing together pieces of film (both for text and image halftones) into large forms for exposure to light-sensitive printing plates. The craft of stripping has disappeared since the introduction of digital prepress.
subtractive color: see primary colors
tintype: an autopositive photographic print on a piece of blackened iron, in effect a less expensive version of the ambrotype.
transparent colors: watercolor paints, some oil paints, and most modern printing inks are transparent. “Full color” process printing, using three primary colors (and black), depends on the overlay of transparent inks to produce a wide array of secondary colors.
trapping: in printing images in more than one color from more than one plate, the practice of enlarging elements of the image so as to produce a dark line where colors overlap, in order to avoid the more distracting white line that otherwise might result from imperfect registration.
web press: a printing press that uses rolls of paper instead of sheets. Web presses can achieve speeds of 50,000 impressions per hour.
wet-plate process: a photographic negative process, introduced in 1851, in which light-sensitive silver compounds are held in a collodion coating on a glass support. Sensitive only while damp, this material has superb tonal rendition but demands an accessible darkroom for coating the plate immediately before exposure and developing it immediately afterward.
wood engraving: a relief printing process that uses an end-grain wooden block. The carving on a wood engraving is usually done with a burin.
woodburytype: a photographic print made with a lead mold generated from a carbon-printed positive. This mold is filled with pigmented gelatin and is pressed onto a paper support to make the print. Relatively inexpensive because it required no silver, the process enjoyed a vogue in the last third of the nineteenth century.
woodcut: a relief printing process that uses a side-grain wooden block. The carving is usually done with gouges or chisels.