Web Site Glossary

acutance
The power to resolve detail in the transition of edges. See also sharpness.




AE (auto exposure)
A mode in the camera that adjusts the shutter speed, the aperture, or both by using the built-in light meter. These definitions are defined as follows: Programmed AE (P mode), where the camera sets both aperture and shutter speed; Aperture Priority AE (A mode), when the user sets the aperture and the camera finds the most appropriate shutter speed; and Shutter Priority AE (S mode), when the speed of the shutter is set by the user and the aperture by the camera.




AF (auto-focus)
When applied to a lens, AF allows the lens to focus automatically on an object within its focusing sensors. When AF is attached to an auto camera body, you don't need to use the aperture ring in auto modes. When applied to a camera, AF means that it is equipped with auto-focus capability and an auto-focus lens.




ambient light
The available natural (sun-lit) light in a scene.




American Standards Association
See ASA.




angle of view
The portion of a scene that is covered by a lens or viewfinder. This is determined by the focal length of a lens and film format.




aperture
The lens opening through which light passes to expose the film. The size of aperture is either fixed or adjustable. Aperture size is usually calibrated in f-numbers—the higher the number, the smaller the amount of light that passes to make the exposure.




aperture priority
Aperture Priority Auto Exposure (A mode). A mode of automatic exposure in which the photographer selects the aperture and the camera sets the shutter speed. This is the most used mode because it is the appropriate one for accurate depth of field control.




ASA (American Standards Association)
Used in conjunction with a number, such as ASA 200, to refer to film "speed" or light sensitivity. The higher the number, the more sensitive the film is to light, allowing for faster shutter speeds or smaller f-stops. ASA has been replaced by ISO, but the scale remains the same. See also ISO (International Organization for Standardization).




auto-focus
See AF (auto-focus).




automatic exposure
A mode of camera operation in which the camera adjusts the shutter speed, the aperture, or both to produce the correct exposure.




automatic white balance (AWB)
Digital cameras come with an automatic white balance meter that essentially tells the camera which intensity of the color white is in the picture. The rest of the colors in the spectrum are adjusted accordingly to make the image look as natural as possible.




available light
Existing light surrounding a subject. It can be natural or artificial, but the photographer does not add it, as with strobes or flash photography.




AWB
See automatic white balance.




backlighting
Light coming from behind the photo subject. Backlighting can cause underexposure of the main subject with auto exposure systems, lending itself to the use of fill-flash or spot metering.




barrel distortion
See distortion.




bellows
A flexible, light-tight, and usually accordion-folded device mounted on cameras that allows the lens to move toward or away from the film plane for greater magnification than with the lens alone. It is usually employed for close-up or macro work.




bit
A bit, which stands for binary digit, is the smallest unit of digital information. Eight bits equal one byte. Digital images are often described by the number of bits that represent each pixel. That is, a 1-bit image is monochrome; an 8-bit image supports 256 colors or gray scales; and a 24- or 32-bit image supports true color.




blur
Also known as ghosting. This effect is caused by an excessive movement of the camera, a zoom lens, or the subject. Blur is often intentional in creative photography to convey the feeling of motion. Blur or ghosting can also be the result of slow shutter speed or slow flash duration in flash photography.




brightness
(1) The balance of light and dark scenes in an image. (2) The amount of light that is reflected by a surface. (3) The intensity or quantity of light emitted from a light source. (4) The condition or quality of luminance from a color.




buffer
Temporary memory area that stores data before it is written into a permanent area. In digital cameras, buffer refers to the memory where images are stored before they are written to the memory card.




built-in meter
A reflected-light exposure meter built into a camera so that light readings can be made directly from the camera position.




camera
A picture-taking device usually consisting of a light-tight box or container, a film cartridge or memory card (image) holder, a shutter to allow a measured quantity of light, and a lens to focus the image.




cartridge
A light-proof film container, made of metal or plastic, that permits a roll of 35-mm film to be loaded into a camera in the light. It is often called a magazine or cassette.




cassette
See cartridge.




CCD (charged coupled device)
A semiconductor device that is often used as an optical sensor. It stores charge and transfers it sequentially to an amplifier and detector used in digital cameras to capture an image.




charged coupled device
See CCD.




chrome
A trade term for color transparency film.




close-up
A larger-than-normal image that is formed by focusing the subject closer than normal to the lens with the use of supplementary lenses, extension tubes, or bellows.




CMOS (complementary metal-oxide semiconductor)
A method of constructing transistors that produces microchips that run with relatively low power consumption. This type of image sensor chip is replacing the CCD. See also CCD (charged coupled device).




CMYK
Acronym for cyan (process blue), magenta (process red), yellow, and black, the primary colors of ink used to create color prints from typical printers. CMYK is not to be confused with the primary colors of light, which are red, green, and blue (RGB).




collimation
The precise alignment of lens optics in relation to the film or image plane of a camera body. This term describes the parallelism of a camera body lens mount to the film plane.




color
The property of objects (or light sources) described in terms of a person's perception of red, blue, green, or other shades and lightness (or brightness) and saturation.




color balance
(1) The ability of media to reproduce accurately the colors of a scene. Color films are balanced for use with specific light sources. (2) The reproduction of colors in a color print, alterable during printing or post-processing.




color cast
A slight trace of one color in all the colors in an image.




color reversal
See positive.




color temperature
Measured in Kelvin (K) degrees, the temperature at which a blackbody emits radiant energy that is competent to evoke a color the same as that evoked by radiant energy from a given source (as a lamp). Photographers need to understand how light changes and film records it so that they can filter it to fit the film in use. Average noon daylight has a color temperature of 5500 K. A common tungsten house light bulb has a color temperature of 2800 K. Tungsten studio lamps measure 3200 K, and photo lamps or photofloods measure 3400 K.




CompactFlash card
Trademark name for one type of digital camera's reusable memory card on which images taken by the camera are stored. It is available in a wide range of storage capacity and recording speeds.




continuous servo auto focus (AF)
An especially useful AF mode when you are focus tracking fast-moving subjects. Using this mode, you can release the shutter at any time, even if the picture is not in focus. As long as the shutter is activated while half depressed, this mode keeps a subject in focus and makes calculations to the subject's positioning at the moment of firing. The setting is typically stated as AF mode "C" on cameras.




continuous tone
Describes an image containing a range of tones from black through many intermediate shades of gray to white.




contrast
The apparent difference in darkness or density between one tone and another. Contrast also refers to the gradual shade difference between black and white. Fewer gray values are described as "high contrast." Many shades of gray are considered low contrast.




convergence
The phenomenon in which lines that are parallel in a subject, such as the vertical lines of houses or buildings, appear nonparallel in a photo.




copyright
A form of protection provided by the laws of the United States (title 17, U.S. Code) and other countries to the authors of "original works of authorship," including literary, dramatic, musical, artistic, and certain other intellectual works. This protection is available to both published and unpublished works. Section 106 of the 1976 U.S. Copyright Act generally gives the owner of copyright the exclusive right to do and to authorize others to reproduce, distribute, perform the work, or display it. These laws are similar in all countries. Copyright is also considered a legal right of creative artists or publishers to control the use and reproduction of their original works.




crop
To trim the edges or enlarge a portion of an image to improve the composition.




curves
A function in Adobe Photoshop that allows a change of the tonal range of a digitized image. It permits anything from simple modifications in shadows, highlights, and midtones to complicated adjustments at any point within a 256-color (from 0 to 255) tonal range of the entire image or precise modifications to the individual color channels of an image.




darkroom
A light-tight room where photographs are developed or printed. In this room, a photographer is able to handle light-sensitive materials without causing unwanted exposure.




daylight
Ambient light with a color temperature of 5500 K. Average daylight, combined with the reflected light from the sky, produces natural ambient light.




depth of field
The area between the nearest and farthest points from the camera that are acceptably sharp in the focused image. This can also be identified as the zone of acceptable sharpness in front of and behind the subject, on which the lens is focused. Depth of field varies according to lens focal length, aperture, shooting distance, and many other factors.




depth of focus
The small range of error within which a sufficient sharp image is produced when a lens is focused.




diaphragm
The mechanism controlling the brightness of light that passes through a lens. An iris diaphragm has overlapping metal leaves whose central opening can be adjusted to a larger or smaller size. See also aperture.




digital
A device or system that uses binary information that can be stored and processed. This binary information has two states, where 0 is on and 1 is off. These states are translated into data called bits. See also bits.




digital camera
A camera that captures an image through the lens on an electronic image sensor, a CCD, or a CMOS chip. The image is then temporarily transferred to a memory buffer and stored onto a FlashCard for eventual download and manipulation on a computer.




digital noise
See noise.




digitization
To store and process the transformation of analog data to digital data.




DIN
Stands for Deutsches Institut für Normung, the German Institute for Standardization that was founded in 1917. It's a numerical rating used in Europe that describes the sensitivity of a light-sensitive material to light. The DIN rating increases by 3 as the sensitivity of the light-sensitive material doubles.




distortion
The effect of straight lines not being rendered perfectly straight in an image. Two types of distortion exist: barrel and pincushion.




dots per inch
See DPI.




download
The process of transferring computer data from one location to another, such as digital images from the camera's memory card onto a computer, from a computer to a memory device such as a CD-ROM, or files from the Internet onto a computer.




DPI (dots per inch)
As applicable to the resolution of a printer, the number of dots it can print per inch. The higher the number, the higher the resolution. Inaccurately, this term is also applied to scanners and digital cameras instead of PPI (pixels per inch), as if a dot were equivalent to a pixel.




electronic flash
See flash.




existing light
Available light. Covers all natural lighting from moonlight to sunshine. Photographically speaking, existing light is the light that is already present on the scene or project, or scenes that are artificially illuminated after dark.




exposure
The amount of light that reaches film or the combination of f-stop and shutter speed that controls the amount of light reaching the light-sensitive material. In addition, this term describes an exposed piece of film. See also f-stop numbers; shutter speed.




exposure compensation
Often referred to as EV compensation by deliberately changing the exposure settings recommended by a light meter to obtain a different exposure to fit a personal preference, create special effects, or meet special requirements.




exposure meter
An instrument that measures the amount of light falling on a subject (incident-light meter) or emitted or reflected by a subject (reflected-light meter), allowing aperture and shutter speed settings to be computed. This is commonly called a light meter. Many light meters are also capable of metering flash or strobe exposures.




extension tubes
Provides additional extension to make the lens focus at closer distances and produce higher magnification. Extension tubes are usually manufactured with metal tubes. They have a rear-lens mount at one end and a camera-body mount at the other end.




factor
A number that tells how many times the exposure must be increased to compensate for loss of light (for example, because of use of a filter or converter).




fast film
A film that has high sensitivity to light, needing less light to obtain a proper exposure. Fast film is recommended for action and low-light photography. This term is normally applied to films that have ISO 400 and higher.




fast lens
A lens that has a maximum wide aperture and low f-number, allowing it to gather more light than a slow lens, which has a narrower open maximum aperture, such as f/3.5, f/4, and smaller.




file format
A common computer-related term to describe programs or data file types such as JPEG, PSD, TIFF, PDF, PICT, or EPS.




film
A photosensitive material that is used in a camera to record an image. Film is made from a thin, transparent base coated on a flexible acetate or plastic base covered with light-sensitive chemicals.




film speed
The relative sensitivity of a film to light. Several rating systems are available: ISO/ASA (the most common in the United States and Great Britain), DIN (common in Europe), and others. Film speed ratings increase as the sensitivity of the film increases. ISO is the contemporary term.




filter
(1) A piece of colored glass, plastic, or other material that selectively absorbs some of the wavelengths of light passing through it. (2) To use such a filter to modify the wavelengths of light reaching a light-sensitive material.




fisheye lens
A lens that has an extremely wide angle of view (as much as 180°) and considerable barrel distortion.




fixed focal length
A nonzoom camera lens that has an unchangeable focal length.




flash
An artificial light source, such as a flashbulb. Flash is often called strobe or electronic flash.




flash duration
The duration of a flash burst from an electronic flash or strobe light.




flash card
A removable memory device that is capable of storing the image data after the system is turned off.




flash range
The distance range within which an artificial light is capable of rendering well-illuminated subjects for proper exposure. The range is a function of both the maximum and minimum flash output capability of the unit and the aperture selected, whether automatically or manually. Flash range is also affected by the ISO speed in use.




flash sync (synchronization)
The shutter speed that corresponds to the proper timing of the flash. If the flash sync is too fast, the shutter won't be open for the duration of the flash. If it's too short, the subject movement might cause blur.




f-number
A scale that expresses the relative area of the aperture of a lens, which is the result of dividing the focal length of the lens by the effective aperture of the lens opening (the apparent size of the diaphragm seen from the front of the lens). The f-number, or f-stop, increases by the multiple of the square root of 2, or 1.4142, from 1.0, 1.4, 2.8, 4, 5.6, 8, 11, and so on, allowing each setting to pass half the light of the aperture below and twice the light of the aperture above in the scale.




focal length
The distance from the lens to the focal plane when the lens is focused on infinity. Generally for 35-mm format, lenses that have a focal length of approximately 50 mm are called normal or standard. Lenses that have a focal length of approximately 35 mm or less are called wide-angle. Finally, lenses that have a focal length of more than approximately 90 mm are called telephoto lenses.




focus
To move the lens or position it in a way enabling light rays to converge so that you can record a sharp image on the film.




focus mode
For contemporary professional digital cameras, three basic types of focus modes exist: Single servo AF (S), Continuous servo AF (C), and Manual AF (M).




focus priority
A camera mode in which the shutter cannot be released until the subject is in focus, as when using Single servo AF (S).




focus tracking
An advanced feature whereby a camera's microprocessor analyzes a moving subject's speed by anticipating the position of the subject at the exact moment of exposure, and drives the lens to that position based on the information.




foreground
The area between the camera and the subject.




format
The size of the camera or the size of the film. Camera sizes come in APS, 35 mm, medium, and large format. Film formats come in APS, 35 mm, 645, 6x6, 6x7, 6x9, 4x5, 5x7, 8x10, and so on.




freeze focus
A feature by which the shutter is automatically actuated when the subject reaches the preset focus point. See also preset focus.




frontlighting
Light shining on the side of the subject who is facing the camera.




f-stop
See f-number.




f-stop numbers
A number that equals the focal length of a lens divided by the diameter of the aperture at a given stop. The larger the number, the smaller the opening of the lens; the smaller the number, the larger the opening of the lens.




FTP (File Transport Protocol)
A protocol that allows users to copy files between their local system and any system they can reach on a network or on the Internet.




ghosting
See blur.




grain
The granular appearance of an image. Grain becomes more pronounced when you're using faster film speeds and when you enlarge an image.




gray scale
An image made up of varying tones of black and white but no color. Grayscale is synonymous with black and white. The gray-level system divides the gray scale into 256 sections, with black at 0 and white at 255.




grip
A worker who moves the camera around while a film or television show is being made. Grip is a common term for a photo assistant in the photography industry who possesses knowledge of cameras and lighting.




highlights
The brightest or whitest parts of an image.




histogram
A graph defining the contrast and dynamic range of an image.




hue
Color or gradation of color. Hue also refers to the attribute of colors that permits them to be classified as red, yellow, green, blue, or an intermediate between any contiguous pair of these colors.




image
A scene that is represented by a two-dimensional medium.




image editor
Allows adjustments to an image to improve its appearance using computer software. With image-editing software, you can darken or lighten a photo; rotate it; adjust its contrast, colors, hue, and saturation; crop out extraneous detail; remove red eye; and more. Adobe Photoshop is the professional image-editing standard.




image resolution
The number of pixels in a digital photo.




incident light
Light as measured as it falls on a subject or surface, instead of light being reflected from a surface.




infinity
The farthest position on the distance scale of a lens. In relation to camera focus, this refers to the horizon.




International Organization for Standardization
See ISO.




ISO
The letters actually stand for International Standards Organization, which also refers to a film's sensitivity to light, or more commonly, its speed. The term is pronounced by the individual letters: I-S-O. It is not considered an acronym, but a word derived from the Greek isos, meaning equal. The early term was ASA, which stood for American Standards Association.




Joint Photographic Experts Group
See JPEG.




JPEG (Joint Photographic Experts Group)
A digital image file format standard in which the size of the file is reduced by compression. A JPEG image file name carries the extension JPG. JPEG compression is loosy, which means that it loses some image information as opposed to other formats, such as TIFF. A high-quality JPEG file loses less than a low-quality JPEG file.




K (Kelvin)
Thermodynamic temperature scale measurement. In photography, it is a numerical description of the color temperature of light at different wavelengths. In 1933, the International Committee of Weights and Measures adopted the temperature at which water, ice, and water vapor coexist in equilibrium as a fixed point, the triple point of water; its value was set as 273.16. The unit of temperature on this scale is called the Kelvin, after William Thompson Lord Kelvin, and its symbol is K (no degree symbol used).




LCD (liquid crystal display)
An information display method. Usually used for external displays on cameras, speedlights, or other electronic devices, such as flat-screen computer monitors.




lens
A piece or several pieces of optical glass shaped to control and focus a subject's light..




lens flare
The soft effect that is visible in a picture as a result of stray light that passes through the lens but is not focused to form the primary image. You can control flare by using optical coating, light baffles, low reflection surfaces, or a lens hood.




lens hood/shade
A lens addition, ring, or tube in front of the lens that minimizes lens flare.




lens speed
The maximum aperture of a lens. A lens that has a wide aperture (such as f/1.4) is called fast because it transmits more light than a slow lens (such as f/5.6).




light box
A device for viewing film. This box uses sunlight-balanced fluorescent tubes and is covered with glass or a plastic surface on which film negatives and positives are placed for viewing.




light meter
See exposure meter.




liquid crystal display
See LCD.




loupe
A small magnifying glass for viewing slides, negatives, and contact sheets. 8X to 10X are common loupes.




magazine
See cartridge.




magnification
The size of an image relative to that of the subject, as expressed in a ratio.




manual camera
A camera that lacks autofocus capability. You can use AF lenses on manual cameras, but you need to focus them by hand.




manual mode
Mode on the camera when the automatic capabilities are disabled. Used for complete control when a camera user wants to manually set both the aperture and shutter speed settings.




MB
See megabyte.




media
Material that data or images are captured to and stored upon. Items such as CompactFlash cards and CDs are referred to as common storage media used with digital photography.




megabyte (MB)
A measurement of data storage that equals 1024 kilobytes (KB).




megapixel
One million pixels.




meter
Any measuring device. In photography, it is commonly referred to as a light meter, although it could also refer to a color meter.




mode
Type of exposure method used by a camera. Common modes include Manual mode (M), Aperture Priority mode (A), picture mode, and flash mode.




monochromatic
Tending toward one color. A monochromatic image is one displaying only black-and-white or grayscale information.




monopod
Single-legged camera support. A monopod is a good substitution for handholding telephoto lenses while allowing mobility.




motor drive
A device for automatically winding and rewinding the film in a camera. Most contemporary professional cameras have motor drives built in. Another term for motor drive is motor winder or speed winder.




motor winder
See motor drive.




negative film
A photographic film that has been exposed to light and processed in a way that the image is reversed; the shadows are light and the highlights are dark.




noise
Also known as digital noise, this is the random colored pixels that appear in dark or shadow areas when the light levels are below the camera's CCD sensitivity range.




Noise Ninja
Noise Ninja is a Photoshop plug-in that removes noise from your photographs.




normal lens
A lens where the focal length is approximately equal to the diagonal of the film size that it's being used for. This is also representative of the same angle of view and perspective of the human eye. In 35-mm format, the normal lens is approximately 50 mm; in medium format, it's approximately 90 mm; and in 4[ts]5 format, it's approximately 200 mm.




overexposure
Light-sensitive material that has been exposed with too much light to obtain a properly exposed image.




panning
The act of following a moving subject as you release the shutter that allows the object to remain sharp and the background to be blurred.




perspective
The apparent size and depth of objects within an image.




photography
From the Greek Photos and Graphos, photography is light writing or writing with light. It's the mix of art, craft, and science for the creation of images on a light-sensitive surface.




PICT
A Macintosh graphic imaging file format using a PCT extension. PICT can contain object-oriented and bitmapped graphics.




pixel
Short for picture element. This refers to any of the small, discrete elements that together constitute an image (as on a computer CRT or television screen), or any of the detecting elements of a charge-coupled device used as an optical sensor in a digital camera.




positive
Any image that has tones corresponding to those of the subject matter. Positive also refers to a slide, transparency, or color reversal film.




PPI (pixels per square inch)
A measurement regarding image quality. The greater the number, the better the image quality.




preset focus
To focus at a predetermined distance when shooting a moving subject as it goes by the focus point. This technique is employed with both manual lenses and when locking focus with auto lenses in anticipation of fast-moving subjects. See also freeze focus.




primary colors
Red, yellow, and blue, the three colors that make white light when they're combined.




prime lens
A lens that has a single, fixed focal length; not a zoom lens.




processing
In photography, a chemical process in which an undeveloped photographic image is converted to a stable visible image.




pulling
Overexposing and underdeveloping film to effectively reduce its speed or ISO. See also pushing.




pushing
Underexposing and overdeveloping film to effectively increase its speed or ISO. See also pulling.




RAW
The data from a digital camera as it comes directly off the CCD, with no in-camera processing performed.




recycle time
The time that it takes for an electronic flash, strobe, or battery pack to recharge so that it can power a flash burst.




red, green, and blue
See RGB.




relative aperture
Diameter of the aperture divided by the focal length of the lens. This is expressed numerically as an f-stop.




release-priority AF
A camera mode option in which the shutter can be released at any time, whether the subject is in focus or not. This is used in fast-moving situations where you don't want to lose any of the action due to shutter release delay.




resolution
The ability to reproduce small details in a photograph. Resolving power measures lens performance using line pairs per millimeter (1/mm) and indicates how many black pairs of lines placed at equal intervals within 1 mm can be resolved by a lens. This is also known as resolving power.




resolving power
See resolution.




retouching
Altering a finished print, digital image, or piece of film to cover up unwanted spots, marks, or elements.




RGB (red, green, and blue)
The three colors to which the human visual system, digital cameras, and many other devices are sensitive; the colors that are used in displays and input devices. These colors represent the additive color model, where 0% of each component yields black, and 100% of each component yields white.




sharpness
The amount of detail that you can perceive in an image, or its focus and contrast. It's the combination of resolution (which is typically measured in terms of the number of distinguishable line pairs per millimeter) and acutance.




shutter
Blades, a curtain, plate, or some other mechanical device in a camera that controls the time that light is permitted to reach the film.




shutter priority
A camera automatic exposure mode that allows a photographer to choose the shutter speed while an electronic processor in the camera adjusts the aperture for best exposure.




shutter speed
The amount of time that the shutter stays open. The shutter speed controls the amount of time that light is allowed to expose the image on the film or sensor.




single lens reflex (SLR) camera
A camera in which the image formed by the lens is reflected by a mirror onto a ground-glass screen for viewing purposes. With this camera, you can view the scene through the same lens that takes the picture.




single-servo auto focus (AF)
When the subject comes into focus, the focus operation stops and stays locked as long as the shutter release button is lightly depressed. Single-servo AF mode is commonly used when shooting stationary objects.




skylight filter
Filter that removes more UV light (and therefore excessive blue) than a UV filter, adding a slight warming tone in two grades—1A and 1B—where B is the warmer one.




slave
A light-sensitive trigger device that synchronizes strobes or flashes without an electronic synch cord.




slide
See positive.




slow lens
A lens that has a small aperture (such as f/8), which allows you to use a slower shutter speed than when using a fast lens.




speed winder
See motor drive.




strobe
A high-intensity flashing beam of light produced by charging a capacitor to a high voltage and then discharging it as a high-intensity flash of light in a tube.




Tagged Image File Format
See TIFF.




teleconverter
A device, consisting of optical glass, that increases the effective focal length of a lens. Mounted between the camera and the lens, a teleconverter typically is available in two different sizes: 1.4X and 2.0X. A 1.4X teleconverter increases focal length by 1.4 times, whereas a 2.0X teleconverter increases focal length by 2.0 times. The aperture of the lens is increased by the same amount as the focal length. For example, a 2.0X teleconverter increases the focal length of a 300-mm lens to 600 mm; however, if the aperture of the lens is f/2.8, it is automatically decreased to f/5.6.




telephoto lens
A lens that has a focal length that is longer than the diagonal of the film format being used. A telephoto lens makes a subject appear larger on film than does a normal lens at the same camera-to-subject distance. It has a narrower field of view than a normal lens does.




through the lens
See TTL.




thumbnail
A small version of a digitized image. Image browsers and image editors commonly like to display thumbnails of several photos at a time. In Windows XP's My Pictures, you can view thumbnails of photos in both the thumbnails and filmstrip view modes. Camera Bits' image browser, Photo Mechanic, displays all images as thumbnails that you can then enlarge for better viewing.




TIFF (Tagged Image File Format)
An uncompressed no-loss image format.




tone
The strength of grays between black-and-white values in an image.




transparency
See positive.




TTL (through the lens)
Automatic flash output control, which uses a light sensor to measure the flash intensity and is read through the lens as reflected by the subject. The result is the flash turning off at the correct exposure.




underexposure
Allowing too little light to reach a photo-sensitive material. The result is a thin or light image with negative material and a dark or dense image with reversal material, such as slide film.




variable focus lens or variable focal length lens
A zoom lens that has a focal length capable of varying from 28 to 100 mm, from landscapes to portraits.




white balance
The technical method for digital cameras to adapt to the color temperature of the dominant light source in a scene. It's the way in which a digital camera compensates and determines the different colors that are being emitted by the source of light.




wide-angle lens
A lens that has a focal length that is less than the diagonal of the film format it's being used with. This lens has a shorter focal length and a wider field of view than a normal lens.




zoom lens
A lens that has an adjustable focal length (70–200 mm), which allows for a closer or farther view of a subject. It changes the magnification, not the perspective.