A substance with a pH below 7. Since an acid neutralizes an alkali, a stop bath is usually an acidic solution that stops that action of the alkaline developer.

Wide-angle distortion

A change in perspective caused by using a wide-angle (short-focal-length) lens very close to a subject. Objects appear stretched out or further apart than they really are.

Wetting agent

A chemical solution, such as Kodak Photo-Flo, used after washing film. By reducing the surface tension of the water remaining on the film, it speeds drying and prevents water spots.


To shade the edges of an image so they are underexposed. A lens hood that is too long for the lens will cut into the angle of view and cause vignetting.

Viewing screen

The surface on which the image in the camera appears for viewing. The image appears upside down and reversed left to right unless the camera contains a pentaprism to correct it.

View camera

A camera in which the taking lens forms an image directly on a ground-glass viewing screen. A film holder is inserted in front of the viewing screen before exposure. The front and the back of the camera can be set at various angles to change the plane of focus and the perspective.


To expose film or paper to too little light. Underexposing film produces a negative that is too light (thin) or a transparency that is too dark. Underexposing paper produces a print that is too light.

Twin-lens reflex

A camera in which two lenses are mounted above one another. The bottom (taking) lens forms an image to expose the film. The top (viewing) lens forms an image that reflects upward onto a ground-glass viewing screen. Abbreviated TLR.

Tungsten film

Color film that has been balanced to produce colors that look natural when exposed in light from an incandescent bulb, specifically light of 3200 K color temperature.


Describes a negative or an area of a negative where relatively little silver has been deposited. A thin negative transmits a large amount of light. The opposite of dense.

Telephoto effect

A change in perspective caused by using a long-focal-length lens very far from all parts of the scene. Objects appear closer together than they really are.

Tacking iron

A small electrically heated tool used to melt the adhesive in dry-mount tissue, attaching it partially to the back of the print and to the mounting surface. This keep sthe print in place during the mounting procedure.

Stop bath

An acid solution used between the developer and the fixer to stop the action of the developer and to preserve the effectiveness of the fixer. Generally a dilute solution of acetic acid; plain water is sometimes used instead of a stop bath for film.


1. An aperture setting that indicates the size of the lens opening. 2. A change in exposure by a factor of 2. Changing the aperture from one setting to the next doubles or halves the amount of light reaching the film. Changing the shutter speed from one setting to the next does the same thing. Either changes the exposure one stop.

Spot meter

An exposure meter with a narrow angle of view, used to measure the amount of light from a small portion of the scene being photographed.


To remove small imperfections in a print caused by dust specks, small scratches, or the like. Specifically, to paint a dye over small white blemishes.


1. The relative ability of a lens to transmit light. Measured by the largest aperture at which the lens can be used. A fast lens has a larger maximum aperture and can transmit more light than a slow one. 2. The relative sensitivity to light of photographic film.


The range of radiant energy from extremely short wavelengths to extremely long ones. The visible spectrum includes only the wavelengths to which the human eye is sensitive.


1. Describes an image that is blurred or out of focus . The opposite of sharp. 2. Describes a scene, negative, or print of low contrast. The opposite of hard or high contrast. 3. Describes a printing paper emulsion of low contrast, such as grade 0 or 1.

Single-lens reflex (SLR)

A type of camera with one lens that is used for both viewing and for taking the picture. A mirror inside the camera reflects the image up into the viewfinder. When the picture is taken, this mirror moves out of the way, allowing the light entering the lens to travel directly to the film.

Silver halide

The light sensitive part of a photographic emulsion, including the compounds silver chloride, silver bromide, and silver iodide.


A device in the camera that opens and closes to expose the film to light for a measured length of time.


Describes an image or part of an image that shows crisp, precise texture and detail. The opposite of blurred or soft.


A light used in the darkroom during printing to provide general illumination without giving unwanted exposure.

Roll film

film (2 1/4 inch wide) that comes in a roll, protected from light by a length of paper wound around it. Loosely applies to any film packaged in a roll rather than in flat sheets.

Reversal processing

A procedure for producing a positive image on film (a transparency) from the film exposed in the camera or a positive print from a transparency with no negative involved.

Resin-coated paper

Printing paper with a water-resistant coating that absorbs less moisture than a fiber-base paper, consequently reducing some processing times. Abbreviated RC paper.


A substance added to some types of developers after use to replace exhausted chemicals so that the developer can be used again.


A metal or plastic reel with spiral grooves onto which roll film is loaded for development.

Reducing agent

The active ingredient in a developer. It changes exposed silver halide crystals into dark metallic silver. Also called the developing agent.


To expose film at a higher film speed rating than normal, then to compensate in part for the resulting underexposure by giving greater development than normal. This permits shooting at a dimmer light level, a faster shutter speed, or a smaller aperture than would otherwise be possible.


A test print made for the purpose of evaluating density, contrast, color balance, subject composition, and the like.


1. An image (usually a positive one) on photographic paper, made from a negative or a transparency. 2. To produce such an image.


A small clear spot on a negative usually caused by dust on the film during development or exposure.


A tungsten lamp designed especially for use in photographic studios. It emits light at 3400 K color temperature.


The optical illusion in a two-dimensional image of a three-dimensional space suggested primarily by converging lines and the decrease in size of objects farther from the camera.


A five-sided optical device used in an eye-level viewfinder to correct the image from the focusing screen so it appears right side up and correct left to right.


The difference in point of view that occurs when the lens (or other device) through which the eye views a scene is separate from the lens that exposes the film.


To move the camera during the exposure int he same direction as the moving subject. The effect is that the subject stays relatively sharp and the background become blurred.


To expose film or paper to too much light. Overexposing film produces a negative that is too dark (dense) or a transparency that is too light. Overexposing paper produces a print that is too dark.


Pixels of random colors and brightness, most often appearing in the dark areas of a digital image.

Neutral-density filter

A piece of dark glass or plastic placed in front of the camera lens to decrease the intensity of light entering the lens. It affects exposure but not color.


1. An image with colors or dark and light tones that are opposite of those in the original scene. 2. Film that was exposed in the camera and processed to form a negative image.


A mealy gray area of uneven development in a print or negative. Usually caused by too little agitation or too short a time in the developer.


A polished metallic reflector set inside the camera at 45° angle to the lens to reflect the image up onto the focusing screen. When a picture is taken, the mirror moves out of the way so that light can reach the film.


An area of middle brightness, neither a very dark shadow nor a very bright highlight. A medium gray tone in a print.


Describes a printing paper with a relatively dull, nonreflective surface. The opposite of glossy.

Mat cutter

A short knife blade (usually replaceable) set in a large easy-to-hold handle. Used for cutting cardboard mounts for prints.


A cardboard rectangle with an opening cut in it that is placed over a print to frame it. Also called an overmat.

Manual flash

A nonautomatic mode of flash operation in which the photographer controls the exposure by adjusting the size of the camera’s lens aperture.


The size of an object as it appears in an image. Magnification of an image on film is determined by the lens focal length. A long focal-length lens makes an object appear larger (provides greater magnification) than a short focal length lens.

Macro lens

A lens specifically designed for close-up photography and capable of good optical performance when used very close to a subject.

Long focal length lens

A lens that provides a narrow angle of view of a scene, including less of a scene than a lens of normal focal length and therefore magnifying objects in the image. Often called a telephoto lens.

Lens tissue

A soft lint-free tissue made specifically for cleaning camera lenses. Not the same as eyeglass cleaning tissue.


One or more pieces of optical glass used to gather and focus light rays to form an image.

Leaf shutter

A camera mechanism that admits light to expose film by opening and shutting a circle of overlapping metal leaves.


The amount of over- or underexposure possible without a significant change in the quality of the image.

Latent image

An image formed by the changes to the silver halide grains in photographic emulsion upon exposure to light. The image is not visible until chemical development takes place.


A numerical rating that indicates the speed of a film. The rating doubles each time the sensitivity of the film doubles.

Infrared film

Film that is sensitive to wavelengths slightly longer than those in the visible spectrum as well as to some wavelengths within the visible spectrum.


Designated ∞. The farthest distance marked on the focusing ring of a lens, generally about 50 feet. When the camera is focused on infinity, all objects at that distance or farther away will be sharp.

Hypo clearing bath

A chemical solution used between fixing and washing film or paper. It shortens the washing time by converting residues from the fixer into forms more easily dissolved by water. Also called fixer remover or washing aid.


A common name for any fixer, taken from the abbreviation for sodium hyposulfite, the previous name for sodium thiosulfate (the active ingredient in most fixers).

Hyperfocal distance

The distance to the nearest object in focus when the lens is focused on infinity. Setting the lens to focus on this distance instead of on infinity will keep the furthest objects in focus as well as extend the depth of field to include objects closer to the camera.

Hot shoe

A clip on the top of the camera that attaches a flash unit and provides an electrical link to synchronize the flash with the camera shutter, eliminating the need for a sync cord.


A very light area in a scene, print, or transparency; a very dense, dark area in a negative. Also called high value.


1. Describes a scene, negative, or print of high contrast. 2. Describes a printing paper emulsion of high contrast such as grades 4 and 5.

Guide number

A number rating for a flash unit that can be used to calculate the correct aperture for a particular film speed and flash-to-subject distance.

Ground glass

1. A piece of glass roughened on one side so that an image focused on it can be seen on the other side. 2. The viewing screen in a reflex or view camera.

Gray card

A card that reflects a known percentage of light falling on it. Often has a gray side reflecting 18 percent and a white side reflecting 90 percent of the light. Used to take accurate exposure meter readings (meters base their exposures on a gray tone of 18 percent reflectance).


Describes an image that has a speckled look due to particles of silver clumping together.


1. A kind of flare caused by reflections between lens surfaces. It appears as bright spots the same shape as the aperture (lens opening). 2. A combined blurred and sharp image that occurs when flash is used with bright existing light. The flash creates a sharp image; the existing light adds a blurred image if the subject is moving.


Describes a print having a wide range of tonal values from deep, rich black through many shades of gray to brilliant white.


An optical surface with concentric circular ridges. Used in a viewing screen to equalize the brightness of the image.


An overall density in the photographic image caused by unintentional exposure to light, unwanted chemical activity, or excess heat or age.

Focusing ring

The band on the camera lens that, when turned, moves the lens in relation to the film plane, focusing the camera for specific distances.


1. The point at which the rays of light coming through the lens converge to form a sharp image. The picture is “in focus” or sharpest when this point coincides with the film plane. 2. To change the lens-to-film distance (or the camera-to-subject distance) until the image is sharp.

Focal length

The distance from an internal part of a lens (the rear nodal plane) to the film plane when the lens is focused on infinity. The focal length is usually expressed in millimeters (mm) and determines the angle of view (how much of the scene can be included in the picture) and the size of the objects in the image. A 100mm lens, for example, has a narrower angle of view and magnifies objects more than a lens of a shorter focal length.


Having less-than-normal differences between light and dark areas. The opposite of contrasty.


1.  A short burst of light emitted by a flashbulb or an electronic flash unit to illuminate the scene being photographed. 2. The equipment used to produce this light.


Non-image forming light that reaches the film, resulting in a loss of contrast or an overall grayness in the final image. Caused by stray light reflecting between the surfaces of the lens.


A chemical solution (sodium thiosulfate or ammonium thiosulfate) that makes a photographic image insensitive to light. It dissolves unexposed silver halide crystals while leaving the developed silver image. Also called hypo.

Fisheye lens

An extreme wide-angle lens covering a 180° angle of view. Straight lines appear curved at the edge of the photograph, and the image itself may be circular.

Filter factor

A number, provided by the filter manufacturer, that tells you how much to increase exposure to compensate for the light absorbed by the filter.


1. A piece of colored glass or plastic placed in the camera’s or enlarger’s light path to alter the quality of light reaching the film. 2. To use such a filter.

Film speed

The relative sensitivity to light of photographic film. Measured by ISO (or ASA or DIN) rating. Faster film (higher number) is more sensitive to light and requires less exposure than slower film.

Film advance lever

A device, usually on the top of the camera, that winds the film forward a measured distance so an unexposed segment moves into place behind the shutter.


A roll or sheet of flexible material coated on one side with a light-sensitive emulsion and used in the camera to record an image.


1. Describes a film or paper that is very sensitive to light. 2. Describes a short shutter speed. The opposite of slow.

Extension tubes

Metal rings attached between the camera lens and the body to allow closer-than-normal focusing in order to increase the image size.

Exposure mode

The type of camera operation (such as manual, shutter-priority, aperture-priority) that determines which controls you set and which ones the camera sets automatically. Some cameras operate in only one mode. Others may be used in a variety of modes.

Exposure meter (light meter)

An instrument that measures the amount of light and provides aperture and shutter speed combinations for correct exposure. Exposure meters may be built into the camera or they may be separate instruments.


1. The act of allowing light to strike a light-sensitive surface. 2. The amount of light reaching the film, controlled by the combination of aperture and shutter speed.


To remove a small dark imperfection in a print or negative by scraping away part of the emulsion.


An optical instrument ordinarily used to project an image of a negative onto sensitized paper. More accurately called a projection printer because it can project an image that is either larger or smaller than the negative.


An image, usually a print, that is larger than the negative. Made by projecting an enlarged image of the negative onto sensitized paper.


A thin coating of gelatin, containing a light-sensitive materail such as silver-halide crystals plus other chemicals, coated on film or paper to record an image.

Electronic flash (strobe)

A camera accessory that provides a brief but powerful flash of light. A battery-powered unit requires occasional recharging or battery replacement but, unlike a flashbulb, can be used repeatedly.


A holder to keep sensitized material, normally paper, flat and in position on the baseboard of an enlarger during projection printing. It may have adjustable borders to frame the image to various sizes.

Dry mount

To attach a print to another surface, usually a heavier mat board, by placing a sheet of adhesive dry-mount tissue between the print and the mounting surface. Generally, this sandwich is placed in a heated mounting press to melt the adhesive in the tissue. Some tissues are pressure sensitive and do not need to be heated.

Dry down

To become very slightly darker and less contrasty, as most photographic printing papers do when they dry after processing.


A numerical rating used in Europe the indicates the speed of film. The rating increases by three each time the sensitivity of the film doubles.

Diffusion enlarger

An enlarger that illuminates the negative with light that has been diffused by passing it through a piece of translucent material above the negative.

Diffused light

Light that has been scattered by reflection or by passing through a translucent material. An even, often shadowless, light.

Dichroic head

An enlarger head that contains yellow, magenta, and cyan filters that can be moved in calibrated stages into or out of the light beam to change the color balance of the enlarging light.

Diaphragm (iris diaphragm)

The mechanism controlling the size of the lens opening and therefore the amount of light that reaches the film. It consists of overlapping metal leaves inside the lens that form a circular opening of variable sizes. (You can see it as you look into the front of the lens.) The size of the opening is referred to as the f-stopor aperture.


1. The entire process by which exposed film or paper is treated with various chemicals to make an image that is visible and permanent. 2. Specifically, the step in which film or paper is immersed in developer.


A chemical solution that changes the invisible latent image produced during exposure into a visible one.


Describes a negative or an area of a negative in which a large amount of silver has been deposited. A dense negative transmits relatively little light. The opposite of thin.


A room where photographs are developed and printed, sufficiently dark to handle light-sensitive materials without causing unwanted exposure.

Contrast grade

The contrast that a printing paper produces. Systems of grading contrast are not uniform, but in general grades 0 and 1 have low or soft contrast; grades 2 and 3 have normal or medium contrast; grades 4 and 5 have high or hard contrast.


Traces of chemicals that are present where they don’t belong, causing loss of chemical activity, staining, or other problems.

Condenser enlarger

An enlarger that illuminates the negative with light that has been concentrated and directed by condenser lenses placed between the light source and the negative.

Color balance

1. Film’s response to the colors in a scene. Color films are balanced for use with specific light sources. 2. The reproduction of colors in a photograph.

Close-up lens

A lens attached to the front of an ordinary lens to allow focusing at a shorter distance in order to increase image size.

Changing bag

A light-tight bag into which a photographer can insert his or her hands to handle film safely when a darkroom is not available.

Center-weighted meter

A through-the-lens exposure meter that measures light values from the entire scene but gives greater emphasis to those in the center of the image area.

Cable release

An encased wire that attaches at one end to the shutter release on the camera and has a plunger on the other end that the photographer depresses to activate the shutter. Used to avoid camera movement or to activate the shutter from a distance.


A shutter-speed setting (marked B) at which the shutter stays open as long as the shutter release is held down.

Built-in meter

An exposure meter in the camera that takes a light reading (usually through the camera lens) and relays exposure information to the electronic controls in an automatic camera or to the photographer if the camera is being operated manually.

Bounce light

Indirect light produced by pointing the light source at a ceiling or other surface to reflect the light back toward the subject. Softer and less harsh than direct light.


The light-tight box that contains the camera mechanisms and protects the film from light until you are ready to make an exposure.


Sheets of absorbent paper made expressly for photographic use. Wet prints dry when placed between blotters.

Bleed mount

To mount a print so there is no border between the edges of the print and the edges of the mounting surface.


An accordion-like section inserted between the lens and the camera body. In close-up photography, the bellows allows closer-than-normal focusing, resulting in a larger image.


The supporting material that holds a photographic emulsion. For film, it is plastic or acetate. For prints, it is paper.

Averaging meter

An exposure meter with a wide angle of view. The indicated exposure is based on an average of all the light values in the scene.

Automatic flash

An electronic flash unit with a light-sensitive cell that determines the duration of the flash for normal exposure by measuring the light reflected back from the subject.

Automatic exposure

A mode of camera operation in which the camera automatically adjusts either the aperture, the shutter speed, or both for normal exposure.

Aperture control

The ring on the camera lens (a push button on some models) that, when turned, adjusts the size of the opening in the iris diaphragm and changes the amount of light that reaches the film.

Adapter ring

A ring used to attach one camera item to another; for example, to attach a lens to a camera in reverse position in order to increase image sharpness when focusing very close to the subject.


Optical defect in a lens (sometimes unavoidable) causing distortion or loss of sharpness in the final image.

Depth of Field

The distance between the nearest and farthest points that appear in acceptably sharp focus in a photograph. Depth of field varies with lens aperture, focal length, and camera to subject distance.


The relative amount of silver present in various areas of film or paper after exposure and development.

Contact printing

The process of placing a negative in contact with sensitized material, usually paper, and then passing light through the negative onto the material. The resulting image is the same size as the image on the negative.

Angle of View

The amount of a scene that can be recorded by a particular lens from a given position; determined by the focal length of the lens.


To move a solution over the surface of film or paper during the development process so that fresh liquid comes into contact with the surface.


To make several exposures, some greater and some less than the exposure that is calculated to be correct.