Glossary of 19th Century and Early 20th Century Photographic Terms

The following is a glossary of photographic terms that were in use in early photography, particularly near the start of the twentieth century. This document is very much a work in progress at the time of this writing. The original list of terms printed here comes from an early edition of a Kodak photography book, How To Make Good Pictures, the earliest publishing date appearing to be some time prior to 1915. The list on this page aims to be expanded as necessary however, so as to include numerous terms and products which are no longer commonplace or commonly understood in modern photography.

[Latest Update: September 28, 2020]

• ABERRATION–A defect in a lens causing it to give a distorted image or one not perfectly sharp.
  
  
• ABRASION MARKS–Black lines or marking produced on the surface of a photographic paper by rubbing or pressure. 
  
  
• ACID–A sour substance in crystal or liquid form, being a compound of hydrogen, in which all or part of the hydrogen may be exchanged for a metal, forming a new compound. Acids have the power to decompose most carbonates. 
  
  
• ACHROMATIC–Colorless; applied to a lens whose chemical and visual focus coincide.
  
  
• ACTINIC–The "actinic rays" of light are those which produce chemical changes or photographic action. 
  
  
• ACTINOMETER–A term erroneously applied to a hydrometer which is intended to show the strength of silver bath in grains of silver nitrate per ounce of solution. It is quite often used arbitrarily to measure the strength of sodium sulphite, sodium carbonate and also hypo solution.
  
  
• ACCELERATOR–A chemical added to a developer to bring out the image more quickly–carbonate of soda is commonly employed.
  
  
• AIR BELLS–Bubbles on sensitized surface of prints, produced by immersing the paper face down in the developer, or using too small amount of solution.
  
  
• ALBUMEN PRINT–A photographic print made on a paper that uses albumen (egg whites) as a binder for the light sensitive silver nitrate.
  
  
• ALKALI–The direct opposite of an acid, and with power to neutralize acid and form fresh compounds called salts. Sulphite and Carbonate of Soda. 
  
  
• ANASTIGMAT LENS–One free from astigmatism, or the fault of not bringing vertical and horizontal lines equally well to a focus. 
  
  
• ANHYDROUS–A chemical term signifying that a substance is absolutely free from water. 
  
  
• ASTIGMATISM–A defect in a lens that prevents it from rendering vertical and horizontal lines equally sharp.–See Anastigmat.
  
  
• AUTOCHROME LUMIERE–An early color photography process that was first made available in 1907. The autochrome process used a mosaic of dyed potato starch to achieve positive color glass plates. See Wikipedia. 
  
  
• BACKING–A coating of non-reflecting material applied to the back of a plate, to prevent halation.
  
  
• BATH–A term applied to toning, developing or other solution. 
  
  
• BRONZING–A metallic appearance in the shadows of a print, due to over-printing.
  
  
• BUBBLES–See air bells. 
  
  
• BURNISHER–A device for securing a high gloss or polish on certain photographic papers. 
  
  
• COLLODION PROCESS–An early photographic process, also called the Wet Plate process, in which a glass plate would be covered with collodion, a wet chemical, sensitized with light-sensitive silver nitrate, immediately exposed in a camera, and then developed to produce a negative image. The entire collodion process must be accomplished in approximately fifteen minutes, thus wet plate photographers generally use portable photography studios when working in the field. While a dry-plate collodion process is possible, it is seldom used on account of requiring a substantially higher exposure time.
  
  
• CONCENTRATED–As applied to liquid preparations means that the chemicals which comprise them have been dissolved in the least possible quantity of water.
  
  
• CONTRASTY–A term applied to prints meaning hard, "chalky", extremely black shadows and white highlights; lacking in detail as applied to negatives. 
  
  
• CONVERTIBLE LENS–One whose parts may be differently arranged, or used separately, so as to produce different focal lengths.  
  
  
• COVERING POWER–The limits within which a lens is capable of giving a well defined image. 
  
  
• CURVATURE OF FIELD–A defect in a lens affording sharper definition at the center of the plate than at the edges.
  
  
• DEFINITION–Clearness and sharpness of image. 
  
  
• DENSE–Applied to negatives which have been over-developed.
  
  
• DENSITY–The printing capacity of a negative.
  
  
• DESICCATED–Anhydrous. Dry powder, not crystals. Applied to chemical salts from which all water has been removed.
  
  
• DEVELOPING-OUT PAPER, OR D.O.P.–Sensitized paper upon which the photographic image is invisible until development has taken place. Applied to "gas-light" papers or those printed by artificial light. Generally applied to papers which require longer exposure than Bromide papers.
  
  
• DEPTH OF FOCUS–The power of a lens to render sharply both near and distant objects at the same time.
  
  
• DETAIL–The definition recorded by the lens of the minute parts of a subject.
  
  
• DEVELOPER–A chemical solution employed to bring out or render visible the latent image.
  
  
• DEVELOPMENT–The process of converting the latent or invisible image on a film, plate or paper into a visible image. 
  
  
• DIFFUSED LIGHT–Such as comes from a clouded sky, in contra distinction to direct sunlight. Light which does not strike directly, but is arrested and diffused by some medium such as ground glass.
  
  
• DIFFUSION OF FOCUS–Throwing the image a little out of focus to produce a soft effect.
  
  
• DISTORTION–An incorrect rendering of the image.
  
  
• DODGE–To dodge is to prevent light from striking a portion of a negative when printing by shading that portion with some opaque body.
  
  
• DOUBLET–A lens composed of two separable lenses.
  
  
• EMBOSSING BOARD–A device for producing prints having countersunk margins. 
  
  
• EMULSION–A term applied to the sensitized coating on plates, films or paper, which is acted upon by the light rays.
  
  
• EQUIVALENT FOCUS–The distance from the optical center of a lens to the ground glass when focused on a distant object.
  
  
• EXPOSURE–The act of submitting sensitized surfaces to the action of light.
  
  
• FERROTYPE PLATE–A highly polished enameled plate of thin metal frequently used for obtaining a high gloss on prints, by drying the print with its face in contact with the plate.
  
  
• FIXING–The process of removing the unacted upon silver salts from a negative or print, usually by immersion in a solution of hypo. 
  
  
• FLARE SPOT–A circular patch of light in the center of the image caused by a defect in the lens.
  
  
• FLAT–Lack of vigor or contrast in a negative or print.
  
  
• FLATNESS OF FIELD–That quality in a lens affording sharp impressions at both center and edge of plate.
  
  
• FOCUS–The point at which converging rays of light from a lens meet, forming an image. A picture is said to be in focus when all details are sharp and well defined.
  
  
• FOCUSING SCALE–A graduated scale for different distances, affixed to the base board of a camera, which permits of focusing for any given distance, without using a ground glass screen. 
  
  
• FOG–A deposit of metallic silver all over the plate or film, including those parts which should ot have been affected by light.
  
  
• FORCING–Attempting to bring out detail in an under-exposed film, plate or print, usually by the addition of accelerator–liable to produce fog.
  
  
• FREAKS–Peculiar white markings caused by incorrect developing solutions. 
  
  
• FRILLING–The puckering up and detachment of the film around the edges ; happens oftenest in hot weather, or through too much alkali in the developer. (Easiest avoided by employing tank development.)
  
  
• HALATION–A blurred effect, resembling a halo, usually occurring around a window opening, or other exceedingly strongly illuminated portions of the image ; caused by a reflection of the rays of light from the back of the plate. 
  
  
• HALF-TONES–All graduations between highlights and deepest shadows.
  
  
• HARDNESS–Excessive contrast in negatives or prints, too great difference between lights and shadows.
  
  
• HIGHLIGHTS–The portions of a picture upon which the greatest amount of light is concentrated. The denser portions of a negative or the lightest parts of a print. 
  
  
• HYDROMETER–An instrument for testing the specific gravity of liquids.
  
  
• HYPO–The abbreviation of the term Sodium Hyposulphite, or ore correctly Sodium Thiosulphate, used for fixing plates, films and paper, may be obtained for use in either granulated or crystal form. 
  
  
• IMAGE–The picture thrown by the lens upon the focusing screen, or sensitive film. 
  
  
• INFINITY–A lens is said to be set for infinity when focused at a point beyond which all objects are sharply defined. 
  
  
• INTENSIFICATION–Increasing the density of a negative or print.
  
  
• LATENT IMAGE–The image impressed upon a film or plate by light action, and which is invisible till chemically treated by the process known as development.
  
  
• LATITUDE OF EXPOSURE–That quality in a film or plate which allows of variations in exposure without detriment to the quality of the negative. 
  
  
• LENS–A circular glass or combination of glasses optically ground and polished, mounted in a metal cell.
  
  
• LIGHT FOG–A graying of the image, produced by an unsafe darkroom lamp, or accidental exposure to white light, through a defect in the apparatus. 
  
  
• MILKY–Appearance of some incorrect fixing baths. Often the results of using impure chemicals.
  
  
• NEGATIVE–A photographic image on a plate or film in which the dark portions of the subject appear light, and the light portions dark. 
  
  
• NO-ACTINIC–Those colors or rays of light which do not affect sensitive emulsions. 
  
  
• ORTHOCHROMATIC–Color sensitive. A film or plate is said to be orthochromatic when it is sensitive to colors of the spectrum other than the blue and ultra violet. 
  
  
• OXIDATION–As applied to developer–a deterioration due to the presence of oxygen. An oxidized developer is dark in color and usually causes discoloration of the negative or print.
  
  
• OVER-EXPOSURE–Too long exposure to printing light.
  
  
• OVER DEVELOPMENT–Too long a time in the developing solution. 
  
  
• PIN HOLES–Minute spots or holes in a negative, usually caused by dust settling on the surface before development.
  
  
• PNEUMATIC RELEASE–A rubber bulb and tube connecting with the valve of a shutter, permitting its release when the bulb is pressed.
  
  
• POSITIVE–A term used in contradistinction to negative.
  
  
• P. O. P. OR PRINTING-OUT PAPER–Sensitized paper upon which the image becomes visible on printing and is made permanent by toning and fixing.
  
  
• PRINTING FRAME–A specially constructed frame for making prints. Holds the negative and sensitive paper in contact while printing.
  
  
• PRECIPITATE–A substance which, having been dissolved, is again separated from its solvent and settles to the bottom of the vessel containing it.
  
  
• RACK AND PINION–A screw and rack adjustment for easy and accurate focusing
  
  
• RECTILINEAR LENS RAPID RECTILINEAR LENS or RR LENS or APLANAT LENS–One which does not distort or show curvature of straight lines in the image.
  
  
• REDUCER–A chemical solution for decreasing contrast or density. 
  
  
• REFRACTION–The change in direction of rays of light when passing through a transparents medium.
  
  
• RESTRAINER–A compound or solution that will check or hold back the action of the developer. Potassium Bromide in weak solution is commonly employed. 
  
  
• RETOUCHING–The removal or softening of defects in a negative, by the application of pencil or color.
  
  
• RETOUCHING MEDIUM–A solution of gum and turpentine, applied to the negative, to afford a "tooth"for the lead or color applied
  
  
• REVERSAL–The image or portions of it being positive instead of negative or vice versa. Caused by extreme over-exposure or exposure to white light during development. 
  
  
• SHADOWS–The thinner portions of a negative or the darker portions of a print. 
  
  
• SOFT–Term applied to print or negative; refers to lack of brilliancy or contrast. A "soft" print will contain all possible detail.
  
  
• SOLARIZATION–See bronzing. 
  
  
• SPECTRUM–Solar–The seven colors produced by passing a ray of white light through a prism.
  
  
• SPHERICAL ABERRATION–A lens defect–The inability to bring the marginal and central rays of light to one focus, resulting in a loss of sharpness. 
  
  
• SPOTTING–The filling in of spots or imperfections in a negative or by means of india ink. or color with a fine brush.
  
  
• SQUEEGEEING–Placing wet prints face down on ferrotype plates to obtain high polish.
  
  
• SQUEGEE OR SQUEEGEE–Usually a strip of soft rubber set in a handle, or a rubber roller, and used to place a print in contact with the ferrotype plate.
  
  
• SYMMETRICAL LENS–One whose combination are of similar curves, and whose combinations may be used singly. 
  
  
• TEN PER CENT. SOLUTION–Approximately, a solution made by dissolving one ounce (by weight) of dry chemical in nine fluid ounces of water. 
  
  
• TONE–The shade, hue or degree of color prevailing in a negative or print.
  
  
• THICK–(See Dense.)
  
  
• UNDER-EXPOSURE–Too short an exposure for perfect results.
  
  
• WEAK–Thin, soft, lifeless, lacking contrast.