Digital Photography Glossary
Can’t remember the difference between a pixel and a bit? Resolution and resampling? Turn here for a quick refresher on that digital photography term that’s stuck somewhere in the dark recesses of your brain and refuses to come out and play.
8-bit image: An image containing 256 or fewer colors.
16-bit image: An image containing roughly 32,000 colors.
24-bit image: An image containing approximately 64 million colors.
Additive color: Combining or blending two or more colored lights in order to simulate or give the sensation of another color.
Aliasing: A digital-image defect that gives the picture a jagged look, usually due to a too-low image resolution. See jaggies.
Alpha channels: Selections stored as masks in the form of grayscale images. Fully selected areas appear white, non-selected areas as black, and partially selected areas as shades of gray.
Analog: An effect, representation, or record that is proportionate to a physical property or change.
Anti-aliasing: Smoothing away the stair-stepping in an image or computer typesetting.
Application: A computer program designed to do a certain job.
Archive: To store a permanent copy of something you don’t need to access very often.
Artifacts: Features in an image, introduced during capture or processing, that were not originally present.
Artifact: Noise, an unwanted pattern, or some other image defect caused by an image capture or processing problem.
Attachment: A file that is sent along with an e-mail, such as an image or other complicated or large item.
Background: The bottom layer of an image; the base.
Back up: To make and store second or further copies of computer files.
Bit: Stands for binary digit. It is the basic unit of digital information. Eight bits equals one byte.
Bicubic: interpolation A type of interpolation in which the value of a new pixel is calculated from the values of its eight near neighbors.
Bilinear interpolation: A type of interpolation in which the value of a new pixel is calculated from the values of four of its near neighbors – left, right, top, and bottom.
Black: An area that has no color or hue due to absorption of most or all light.
Bleed: (1) A photograph or line that runs off the page when printed. (2) The spread of ink into fibers of support material; the effect causes dot gain.
BMP: The Windows bitmap graphics format. Reserved today for images that will be used as system resources on PCs, such as screen savers or desktop wallpaper.
Brightness: The quality of visual perception that varies with the amount or intensity of light.
Brush: An image-editing tool used to apply effects such as color, blurring, burn, dodge, and so on.
Burst mode: A special capture setting, offered on some digital cameras, that records several images in rapid succession with one press of the shutter button.
Burning-in: The alteration of the local contrast and density of an image by making certain parts darker. while masking off the rest of the picture.
Byte: A word or unit of digital information.
Byte: Eight bits. See bit.
Calibrate: To adjust a device, like a monitor, m meets certain standards.
Camera exposure: A quantity-of-light sensor. It depends on effective aperture of lens and duration of exposure to light.
CCD: Short for charge-coupled device. One of two types of computer chips used to capture images in digital cameras.
CIE: A color model developed by the Commission International de 1’Eclairange. Used mostly by higher-end digital imaging professionals.
Channel: A set of data used by image-manipulation software to define a color or mask.
Click-drag: To place the mouse pointer over the picture or file you want to move, press the mouse button c, and hold it down as you move the mouse pointer where you want to place the item.
Cloning: The process of copying, repeating, or duplicating pixels from one part of an image or another image on to another.
Cloning: The process of painting one portion of an image onto another image or another part of the same image.
Colorize: To add color to a grayscale image without changing the original lightness values.
CMOS: Pronounced see-moss. A much easier way to say complementary metal-oxide semiconductor. A type of computer chip used to capture images in digital cameras; used less often than CCD chips.
CMYK: Cyan Magenta Yellow Key. The colors of inks used to create a sense of color.
CMYK: The print color model, in which cyan, magenta, yellow, and black inks are mixed to produce colors.
ColorSync: Proprietary color-management software system that helps ensure that colors seen on screes match those to be reproduced.
Color cast: A hint of color evenly covering an image.
Color correction: The process of adjusting the amount of different primary colors in an image (for example, lowering the amount of red in an RGB image).
Color gamut: The range of colors that can be handled or output by a device such as a printer or screen.
Color management: The process of controlling the output of all devices in a production chain.
Color model: A way of defining colors. In the RGB color model, for example, all colors are created by blending red, green, and blue light. In the CMYK model, colors are defined by mixing cyan, magenta, yellow, and black.
Color saturation: This measures how rich or pure color is: highly saturated colors are very pure, and appear strong.
Color Space: An abstract way of showing how afferent colors relate to each other. The most oxmnon color space is that created by RGB.
Color temperature: Refers to the amount of red, green, and blue light emitted by a particular light source.
CompactFlash: A type of removable memory card used in many digital cameras. A miniature version of a PC Card — about the size and thickness of a matchbook.
Compositing: The putting together of parts of different images to create a new one. Its similarity to stacking bits of pictures and other things together gives it the alternative name of collage.
Compositing: Combining two or more images in an image editor.
Compression: A process that reduces the size of the image file by eliminating some image data.
Compression (2): The process of reducing the size of digital files by changing the way the data is coded.
Contrast: This measures the differences between the lights and darks in an image
Crash: The sudden, unexpected, and unwelcome non-functioning of a computer.
Crop (1): To use part of an image for the purpose of, for example, improving composition; fitting an image to available space or format; squaring up an image to correct the horizon. (2) To scan the required part of an image.
Default settings: The settings that a camera or software offers you in the absence of other instructions.
Definition: A measure of how much detail is recorded Low definition equates with not much fine detail being visible; high definition shows fine detail clearly.
Delete: To remove the name of a file from the computer records. The file itself may still be present, so it may be possible to retrieve it.
Depth of field: The space in front of, and behind, the plane of best focus within which objects appear acceptably sharp.
Digital image: Any picture or graphic in digital form. It could be created directly by drawing, but could also be caught in a camera or scanner.
Digital photography: A type of photography in which any stage involves or uses a digital image.
Digitize: To turn an analog record, such as a print, into a digital file – either using a scanner or a digital
Direct-vision finder: A type of viewfinder in which the subject is observed directly – that is, through a hole or optical device.
Display: A device that provides the temporary visual representation of data. Examples: monitor screen, LCD projector, information panel on camera.
Dodging: The selective lightening of parts of the image that would otherwise appear too dark. Compare Burning-in.
Downloading: Transferring data from one computer device to another.
DPI Dots per inch: The measure of the resolution of an output device as a number of dots or points that can be addressed or printed by the device.
DPI: Short for dots per inch. A measurement of how many dots of color a printer can create per linear inch. Higher dpi means better print quality on some types of printers, but on other printers, dpi is not as crucial to quality.
Driver: The software used by a computer to control or drive a peripheral device, such as a scanner, printer, or removable-media drive.
Drop shadow: A graphic effect in which an object appears to float above a surface, leaving a fuzzy shadow below it and offset to one side.
Duotone (1): A photomechanical printing process using two inks to increase tonal range. (2) A mode of working in image-manipulation software that simulates the printing of an image with two inks.
Dye-sub: Short for dye-sublimation. A type of printer that produces excellent digital prints.
Edges: Areas where neighboring image pixels are significantly different in color; in other words, areas of high contrast.
Electronic viewfinder: An LCD screen, viewed under the eyepiece, that shows the view through the camera lens.
EV compensation: A control that slightly increases or decreases the exposure chosen by the camera’s autoexposure mechanism. EV stands for exposure value; EV settings typically appear as EV 1.0, EV 0.0, EV-1.0, and so on.
Exposure: The process of allowing light to reach light-sensitive material to create an image.
F
f/number: A lens-diaphragm setting that determines the amount of light transmitted by the lens.
Feathering: Blurring a border or bounding line by reducing the sharpness or suddenness of the change.
Field of view: (of a lens) This measures the angle of what can be seen at the viewer’s position, from one corner to the opposite corner of the image.
File format: A way of storing image data in a file. Popular image formats include TIFF, JPEG, and GIF.
Fill-in (1): To illuminate shadows cast by the main light by using another light source or reflector to bounce light from the main source into the shadows. (2) To cover an area with color, as achieved by the Bucket tool.
Filter: Software that converts one file format to another or applies effects to the image.
FireWire: The standard for rapid communication between computers and devices. Also called i.Link and IEEE 1394.
Flare: The light that is present in the image but that does not actually help show detail or colors — it is just an unwanted nuisance. It’s caused by stray light bouncing around inside the lens.
FlashPix: A new image file format developed to facilitate the editing and online viewing of digital images. Currently supported by only a handful of software programs.
Flash (1): A very brief burst — less than Wooo of a second in duration – of intense light. This light is added to that from the available, or ambient, light. (2) The equipment used to provide a brief burst or flash of light. (3) A type of electronic memory used in digital cameras.
Flatten: To combine multiple layers and other elements into a background layer.
Focal length: For a simple lens, the distance between the center of the lens and the sharp image of an object at infinity projected by it.
Font: A computer file describing a set of letter forms for display on screen or to be printed.
Format: The shape (or proportion of the length to the width) and the orientation (upright or horizontal) of a picture. Applied to film, it means the size of image.
Gamma: A combined measure of how bright and contrasty the screen image appears
Gamut: Say it gamm-ut. The range of colors that a monitor, printer, or other device can produce. Colors that a device can’t create are said to be out of gamut.
GIF: Pronounced gif, with a hard g. GIF stands for graphics interchange format. One of the two image file formats used for images on the World Wide Web. Supports 256-color images only.
GIF: Graphic Interchange Format. A compressed file format designed lor use on the Internet.
Gigabyte: Approximately 1,000 megabytes, or 1 billion bytes. In other words, a really big collection of bytes. Abbreviated as GB.
Grayscale: An image consisting solely of shades of gray, from white to black.
Grayscale (2): A measure of the number of distinct steps between black and white in a record.
GSM: Grammes per square metre. This measure tells you how much substance paper has, which is roughly proportional to how thick it is.
Hard copy: A visible form of a computer file printed more or less permanently on to a support such as paper or film.
Histogram: A graphical representation showing the relative numbers of something over a range of values.
Hot-pluggable: A connector that can be disconnected or connected while the computer and machine are powered. Examples are FireWire and USB.
HSB: A color model based on hue (color), saturation (purity or intensity of color), and brightness.
HSL: A variation of HSB, this color model is based on hue, saturation, and lightness.
I
Ink-jet Printing: based on the squirting of extremely tiny drops of ink on to a receiving substrate.
Interpolation: See Pixel interpolation. Jaggies The appearance of stair-stepping artifacts.
Jaggies: A nipper term for aliasing. Refers to the jagged appearance of images that have been printed or displayed at too low a resolution.
JPEG: Pronounced jay-peg. One of two formats used for images on the World Wide Web and also used for storing images on many digital cameras. Uses lossy compression, which sometimes damages image quality.
JPEG (2): Joint Photographic Expert Group. A data-compression technique that reduces file sizes with loss of information.
K (1): Binary thousand – that is, 1,024. For example. 1,024 bytes is abbreviated KB, or K. (2) The Key ink in the CMYK process. (3) Degrees Kelvin, which measure color temperature.
Keyboard shortcut: A keystroke to execute a command-Key tone The principal or most important tone in an image, usually the mid-tone between white and black.
Kelvin: A scale for measuring the color temperature of light. Abbreviated as K, as in 5000°K. (But in computerland, the initial AT more often refers to kilobytes, as described next.)
Kilobyte: One thousand bytes. Abbreviated as K, as in 64K.
Layer mode: A picture-processing or image-manipulation technique that determines the way in which a layer in a multilayer image combines or interacts with the layer below.
LCD: Liquid crystal display. A type of display using materials that can block light.
LCD (2): Stands for liquid crystal display. Often used to refer to the display screen included on some digital cameras.
Lossless compression: A file-compression scheme that doesn’t sacrifice any vital image data in the compression process. Lossless compression tosses only redundant data, so image quality is unaffected.
Lossless compression (2): A computing routine that reduces the size of a digital file without reducing the information in the file – for example, LZW.
Lossy compression: A compression scheme that eliminates important image data in the name of achieving smaller file sizes. High amounts of lossy compression damage image quality.
Lossy compression (2): A computing routine that reduces the size of a digital file but also loses information or data – for example, JPEG.
LPI: Lines per inch. A measure of resolution or fineness of photomechanical reproduction.
Luminance range: A term given to the difference between the brightest and darkest parts of the image
LZW compression: A way of reducing file size that does not damage image quality.
Marquee: The dotted outline that results when you select a portion of your image. Also sometimes used as a verb, as in “I’m in the mood to marquee something.”
Marquee (2): A selection tool used in image-manipulation and graphics software.
Mask: To obscure selectively or hold back parts of an image while allowing other parts to show.
Megabyte: One million bytes. Abbreviated as MB. See bit.
Megapixel: Refers to digital cameras that can capture high-resolution images; technically reserved for cameras that can capture 1 million pixels or more.
Megapixel (2): One million pixels; used to describe a digital camera in terms of sensor resolutions.
Menu: A list of options offered by the camera. You must select one to set the camera to that option.
Memory card: An electronic chip encased in a slim plastic casing; it stores information such as image data. Memory cards are often nicknamed “digital film.” There are many kinds and standards.
Memory Stick: a memory card used by several Sony digital cameras and peripheral devices. About the size of a stick of chewing gum.
Metadata: Extra data that gets stored along with the primary image data in an image file. Metadata often includes information such as aperture, shutter speed, and EV setting used to capture the film, and can be viewed using special software.
Metering mode: Refers to the way a camera’s autoexposure mechanism reads the light in a scene. Common modes include spot metering, which bases exposure on light in the center of the frame only; center-weighted metering, which reads the entire scene but gives more emphasis to the subject in the center of the frame; and matrix or multizone metering, which calculates exposure based on the entire frame.
Moire: A pattern of alternating light and dark bands or colors caused by interference between two or more superimposed arrays or patterns that differ in phase, orientation, or frequency.
Monochrome: A photograph or image made of black, white, and grays, which may or may not be tinted.
Morphs: Digital distortions that can be highly and precisely localized.
Navigate: To move through menus until you find and select the control option you are looking for.
Nearest neighbor: A type of interpolation in which the value of the new pixel is copied from the nearest pixel to it.
Noise: Irregularities in an image that reduce the information content.
Noise: Graininess in an image, caused by too little light or a defect in the electrical signal generated during the image-capture process.
NTSC: A video format used by televisions and VCRs in North America. Many digital cameras can send picture signals to a TV or VCR in this format.
Opacity: A measure of how much can be “seen” through a layer.
Operating system: A special type of software that controls the computer itself and the way it interacts with you. It does things like organizing files, managing connected devices, and putting the display on to the monitor.
Optical viewfinder: A type of viewfinder that shows a subject through an optical system, rather than via a monitor screen.
Out-of-gamut: Colors from one color system that cannot be seen or reproduced in another.
Output: A hard-copy printout of a digital file – for example, an ink-jet print.
Paint: To apply color, texture, or effect with a digital “brush.”
PAL: The video format common in Europe and several other countries. Few digital cameras sold in North America can output pictures in this video format (see also NTSC).
Palette: (1) A set of tools, colors, or shapes. (2) A range or selection of colors.
PCMCIA Card: A type of removable memory card used in some models of digital cameras. Now often referred to simply as PC Cards. (PCMCIA stands for Personal Computer Memory Card International Association.)
Peripheral: Any device connected to a computer – for example, printer, monitor, scanner, or modem.
Photo CD: A special image format used for writing images to a CD.
Photomontage: A photographic image made from the combination of several other photographic images.
PICT: A graphic file format used on Mac OS.
PICT (2): The standard format for Macintosh system images. The equivalent of BMP on the Windows platform, PICT is most widely used when creating images for use as system resources, such as startup screens.
Pixel: Short for picture element. The basic building block of every image.
Pixel: Short for picture element. Pixels are the building blocks of the image. Usually square in shape, they are virtual, having no size until they are printed or displayed.
Pixel interpolation: A mathematical process for working out new intermediate values between known ones. It is used to interpose new pixels between existing pixels.
Pixelated: Describes images in which the individual picture elements – square blocks of color – can be easily seen.
Platform: A fancy way of saying “type of computer system.” Most folks work either on the PC platform or the Macintosh platform.
Plug-in: An application software that works in conjunction with a host program into which it is “plugged” so that it operates as if part of the program itself.
Posterization: The representation of an image that results in a banded appearance and flat areas of color.
PPI: Points per inch. The number of points that are seen or resolved by a scanning device per linear inch.
PPI(2): Stands for pixels per inch. Used to state image resolution. Measured in terms of the number of pixels per linear inch. A higher ppi translates to better-looking printed images.
Pre-scan: In image acquisition, a quick view of the object to be scanned, taken at a low resolution for cropping, for example.
Prosumer: A term applied to cameras designed for amateur or hobbyist photographers but capable of making professional-quality images.
RAM: Random Access Memory. The component of the computer in which information can be stored or rapidly accessed.
Raster: The grid-like arrangement of pixels or dots of ink, like that of a chessboard.
Read: To access or remove information from a storage device such as a hard disk or CD-ROM.
Resampling: Adding or deleting image pixels. A large amount of resampling degrades images.
Resolution: The number of pixels per linear inch (ppi) in an image. Generally speaking, higher resolution means better images. Also used to describe printer, screen, or scanner capabilities.
Resizing: Changing resolution or file size of an image.
RGB: Red Green Blue. A color model that defines colors in terms of relative amounts of red, green, and blue components.
RGB(2): The standard color model for digital images; all colors are created by mixing red, green, and blue light.
Rubylith: A red paint applied to negative film that prevents painted areas from being printed out.
Saturation: A measure of intensity; a highly saturated color is said to be pure.
Scan: To use a machine to make a digital copy of your original photograph.
Scrolling: The process of moving to a different portion of a file that is too large for the whole to fit on to a monitor screen.
Selection: A defined area of the image that you can work on and to which you apply effects.
Sharpness: A subjective judgment of how clearly details can be seen in an image.
Sharpening: Applying an image-correction filter inside an image editor to create the appearance of sharper focus.
SLR: Single-lens reflex. This type of camera uses the same lens for viewing as for taking the picture. For focusing and framing, you view the image on a focusing screen; the image you see on the screen is how your photo will turn out.
SmartMedia: A thin, matchbook-sized, removable memory card used in some digital cameras.
Softening: An effect that surrounds sharp outlines with blur, often with more blur at high-contrast edges than at low-contrast ones.
Soft proofing: The use of a monitor screen to proof or confirm the quality of an image.
Stair-stepping: The jagged, rough, or step-like reproduction of a line or boundary that is intended to be smooth.
Suffix: The dot and a few letters added after the file name. It is used by some operating systems.
Telephoto: An optical construction that enables the physical length of the lens to be less than the focal length.
Thumbnail: The representation of an image as a small, low-resolution version.
TIFF: Pronounced tiff, as in little quarrel. Stands for tagged image file format. A popular image format supported by most Macintosh and Windows programs.
Tint (1): A color that can be reproduced with process colors; a process color. (2) An overall, usually light, coloring that tends to affect areas with density but not clear areas.
Tolerance setting: This determines how different a pixel can be before it is ignored. A low tolerance selects very similar pixels; a high tolerance selects a wide range of pixels.
Tone reproduction: In photography, this describes the way in which a record represents the changes of light and dark. When you get it right, it looks convincing and part of the effect of the image.
Transfer functions: These define the way one measure changes as a result of applying an effect — for example, dark tones are made less dark, while light tones become darker. A curve represents these changes through the shape of its line.
Transparency adapter: An accessory light source that enables a scanner to scan transparencies.
TWAIN: Say it twain, as in “never the twain shall meet.” A special software interface that enables image-editing programs to access images captured by digital cameras and scanners.
TWAIN(2): A standardized software “bridge” used by computers to control scanners via scanner drivers.
Undo: To reverse an editing or similar action within application software.
Unsharp masking: The process of using the Unsharp Mask filter, found in many image-editing programs, to create the appearance of a more focused image. The same thing as sharpening an image, only more impressive sounding.
Uploading: The same as downloading; the process of transferring data between two computer devices.
USB: Stands for Universal Serial Bus. A type of high-speed port included on computers. USB ports permit easier connection of USB-compatible peripheral devices such as digital cameras, printers, and memory-card readers.
USB(2): Universal Serial Bus – a standard port design for connecting peripheral devices – for example, a digital camera, telecommunications equipment,or a printer – to a computer.
USM: Unsharp Mask. An image-processing technique that has the effect of improving the apparent sharpness of an image.
Veiling: flare Light – like an overall mist – in the image that does not form the image. It lowers contrast.
Warm colors: Hues such as reds, through oranges, to yellows.
White balancing: Adjusting the camera to compensate for the type of light hitting the photographic subject. Eliminates unwanted color casts produced by some light sources, such as fluorescent office lighting.
Write: To commit data on to a storage medium – for example, a CD-R.
Zip: The proprietary name for a data-storage system.