action
Photoshop keystrokes recorded to automate routine activity.
additive primary colors
The three colors red, blue, and green, which can be combined to create any other color. When superimposed on each other they produce white.
adjustment layer
A layer in a Photoshop image that adjust the appearance of layers beneath it, and keep editing adjustment distinct from the original image data.
aliasing
Jagged edges in a digital image, caused by the square of its constituent pixels.
alpha channel
A grayscale version of the image that can be used with the color channels for saving a mask or selection.
anti-aliasing
Smoothing jagged edges by introducing additional pixels of intermediate tone.
aperture
The opening behind the camera lens through which light passes on its way to the image sensor (CCD/CMOS).
application (program)
Software designed to make the computer perform a specific task. So, image-editing is an application, as is word-processing. System software, however, is not an application, as it controls the running of the computer.
artifact
Foreign shapes degrading a digital image as a result of its capture, manipulation, or output.
backlighting
The result of shooting with a light source, natural or artificial, behind the subject to create a silhouette or rim-lighting effect.
backup
A copy of either a file or a program, for safety reasons, in case the original becomes damaged or lost. The correct procedure for making backups is on a regular basis, while spending less time making each one than it would take to redo the work lost.
ballast
The power pack unit for an HMI light which provides a high initial voltage.
banding
Unwanted effect in a tone or color gradient in which bands appear instead of a smooth transition. It can be corrected by higher resolution and more steps, and by adding noise to confuse that part of the image.
bit (binary digit)
The smallest data unit of binary computing, being a single 1 or 0.
bit depth
The number of bits of color data for each pixel in a digital image. A photographic-quality image needs eight bits for each of the red, green, and blue channels, making for a bit depth of 24.
bitmap (bitmapped image)
Image composed of a pattern of pixels, as opposed to a mathematically defined object (an object-oriented image). The more pixels used for one image, the higher its resolution. This is the normal form of a scanned photograph.
blending mode
The calculation that controls how one Photoshop layer is composited with other layers.
blown out
Containing no detail, usually referring to overexposed parts of an image.
boom
A support arm for attaching lights or fittings to.
bracketing
A method of ensuring a correctly exposed photograph by taking three shots; one with the supposed correct exposure, one slightly underexposed, and one slightly overexposed.
brightness
The level of light intensity. One of the three dimensions of color in the HSB color system. See also Hue and Saturation
buffer
An area of temporary data storage, normally used to absorb differences in the speed of operation between devices. For instance, a file can usually be sent to an output device, such as a printer, faster than that device can work. A buffer stores the data so that the main program can continue operating.
burn
A photographic darkroom and Photoshop technique to darken selective parts of an image.
burned out
Containing no detail, usually referring to overexposed parts of an image.
byte
Eight bits. The basic unit of desktop computing. 1,024 bytes equals one kilobyte (KB), 1,024 kilobytes equals one megabyte.
calibration
The process of adjusting a device, such as a monitor, so that it works consistently with others, such as scanners and film recorders.
catalog
A program that records the contents of folders, displays image files' thumbnails and large previews, and allow metadata entry. While folders may be shown, their contents are not updated in real time, but rather only when instructed, and searches are performed upon the database.
Camera Raw
In Photoshop, the module resonsible for converting Raw images from any digital camera.
CCD (Charge-Coupled Device)
A tiny photocell used to convert light into an electronic signal. Used in densely packed arrays, CCDs are the recording medium in most digital cameras.
channel
Part of an image as stored in the computer; similar to a layer. Commonly, a color image will have a channel allocated to each primary color (e.g. RGB) and sometimes one or more for a mask or other visual effects.
clipping
An absence of detail in image areas because the brightness values record either complete black or pure white.
CMOS (Complementary Metal-Oxide Semiconductor)
An alternative sensor technology to the CCD, CMOS chips are used in ultra-high-resolution cameras from Canon and Kodak.
CMYK (Cyan, Magenta, Yellow, Key)
The four process colors used for printing, including black (key).
color gamut
The range of color that can be produced by an output device, such as a printer, a monitor, or a film recorder.
color temperature
A way of describing the color differences in light, measured in Kelvins and using a scale that ranges from dull red (1900 K), through orange, to yellow, white, and blue (10,000 K).
Reduction of image size by use of algorithms to discard superfluous data.
contrast
The range of tones across an image, from bright highlights to dark shadows.
cropping
The process of removing unwanted areas of an image, leaving behind the most significant elements.
curves
In image editing, a method of mapping pixels' brightness values to the value at which they are output.
depth of field
The distance in front of and behind the point of focus in a photograph, in which the scene remains in acceptable sharp focus.
derivative
An image file produced from an original, for instance the JPEG or PSD file saved after a Raw original has been converted.
destructive
Permanent change of pixels' brightness values, tones, or positions.
dialog box
An onscreen window, part of a program, for entering settings to complete a procedure.
diffusion
The scattering of light by a material, resulting in a softening of the light and of any shadows cast. Diffusion occurs in nature through mist and cloud cover, and can also be simulated using diffusion sheets and soft-boxes.
digital
A way of representing data as a number of distinct units. A digital image needs a very large number of units so that it appears as a continuous-tone image to the eye; when it is displayed these are in the form of pixels.
digital asset management
The practice of downloading, backing up, evaluating, describing, categorizing, selecting, and archiving digital image files.
DMax (Maximum Density)
The maximum density—that is, the darkest tone—that can be recorded by a device.
DMin (Minimum Density)
The minimum density—that is, the brightest tone—that can be recorded by a device.
dodge
A photographic darkroom and Photoshop technique to brighten selective parts of an image.
DPI
Dots per inch, the standard measure of print resolution.
dynamic range
The range of tones that an imaging device can distinguish, measured as the difference between its dmin and dmax. It is affected by the sensitivity of the hardware and by the bit depth.
EXIF
Commonly refers to exposure information stored with digital image files; strictly refers to the file format of this information itself.
ƒ-stop
The ratio of the focal length to the aperture diameter, expressed as ƒ/2.8, ƒ/4, ƒ/5.6, etc.
file format
The method of writing and storing a digital image. Formats commonly used for photographs include tiff, pict, bmp, and jpeg (the latter is also a means of compression).
filter (1)
A thin sheet of transparent material placed over a camera lens or light source to modify the quality or color of the light passing through. (2) A feature in an image-editing application that alters or transforms selected pixels for some kind of visual effect.
focal length
The distance between the optical center of a lens and its point of focus when the lens is focused on infinity.
focal point
The point at which light rays passing through a lens converge.
focal range
The range over which a camera or lens is able to focus on a subject (for example, 0.5m to Infinity).
focus
The optical state where the light rays converge on the film or CCD to produce the sharpest possible image.
fringe
In image-editing, an unwanted border effect to a selection, where the pixels combine some of the colors inside the selection and some from the background.
frontal light
Light that hits the subject from behind the camera, creating bright, high-contrast images, but with flat shadows and less relief.
gamma
A measure of the contrast of an image, expressed as the steepness of the characteristic curve of an image.
gobo
A corruption of “go between,” this is anything used to block or partially block light.
gradation
The smooth blending of one tone or color into another, or from transparent to colored in a tint. A graduated lens filter, for instance, might be dark on one side, fading to clear on the other.
grayscale
An image containing pixels with brightness values only on a black-and-white scale with no color data.
GUI (Graphic User Interface)
Screen display that uses icons and other graphic means to simplify using a computer. The Macintosh GUI was one of the reasons for Apple’s original success in desktop computing.
haze
The scattering of light by particles in the atmosphere, usually caused by fine dust, high humidity, or pollution. Haze makes a scene paler with distance, and softens the hard edges of sunlight.
HDRI (High Dynamic Range Imaging)
A method of combining digital images taken at different exposures to draw detail from areas which would traditionally have been over or under exposed. This effect is typically achieved using a Photoshop plugin, and HDRI images can contain significantly more information than can be rendered on screen or even perceived by the human eye.
histogram
A map of the distribution of tones in an image, arranged as a graph. The horizontal axis goes from the darkest tones to the lightest, while the vertical axis shows the number of pixels in that range.
hot shoe
An accessory fitting found on most digital and film SLR cameras and some high-end compact models, normally used to control an external flash unit. Depending on the model of camera, pass information to lighting attachments via the metal contacts of the shoe.
HSB (Hue, Saturation, Brightness)
The three dimensions of color, and the standard color model used to adjust color in many image-editing applications.
hue
The pure color defined by position on the color spectrum; what is generally meant by “color” in lay terms.
ICC profile
A measure of a digital imaging device's color characteristics, used for accurate communication of color between devices, as set by the International Color Consortium.
interpolation
Bitmapping procedure used in resizing an image to maintain resolution. When the number of pixels is increased, interpolation fills in the gaps by comparing the values of adjacent pixels.
ISO
An international standard rating for film speed, with the film getting faster as the rating increases. ISO 400 film is twice as fast as ISO 200, and will produce a correct exposure with less light and/or a shorter exposure. However, higher-speed film tends to produce more grain in the exposure, too.
JPEG (Joint Photographic Experts Group)
Pronounced “jay-peg,” a system for compressing images, developed as an industry standard by the International Standards Organization.
layer
In image-editing, one level of an image file, separate from the rest, allowing different elements to be edited separately.
LCD (Liquid Crystal Display)
Flat screen display used in digital cameras and some monitors. A liquid-crystal solution held between two clear polarizing sheets is subject to an electrical current, which alters the alignment of the crystals so that they either pass or block the light.
light pipe
A clear plastic material that transmits light, like a prism or optical fiber.
light tent
A tent-like structure, varying in size and material, used to diffuse light over a wider area for close-up shots.
LCD (Liquid Crystal Display)
Flat screen display used in digital cameras and some monitors. A liquid-crystal solution held between two clear polarizing sheets is subject to an electrical current, which alters the alignment of the crystals so that they either pass or block the light.
lossless
Type of image compression in which no information is lost, and so most effective in images that have consistent areas of color and tone. For this reason, not so useful with a typical photograph.
lossy
A file format which discards image information to create a smaller output file. Opposite of lossless.
lumens
A measure of the light emitted by a lightsource, derived from candela.
luminosity
The brightness of a color, independent of the hue or saturation.
lux
A scale for measuring illumination, derived from lumens. It is defined as one lumen per square meter, or the amount of light falling from a light source of one candela one meter from the subject.
macro
A type of lens capable of close-up photography at more than 1:1 magnification.
mask
A grayscale template that hides part of an image. One of the most important tools in editing an image, it is used to make changes to a limited area. A mask is created by using one of the several selection tools in an image-editing program; these isolate a picture element from its surroundings, and this selection can then be moved or altered independently.
midtone
The parts of an image that are approximately average in tone, falling midway between the highlights and shadows.
modeling light
A small light built into studio flash units which remains on continuously. It can be used to position the flash, approximating the light that will be cast by the flash.
monobloc
An all-in-one flash unit with the controls and power supply built-in. Monoblocs can be synchronized together to create more elaborate lighting setups.
neutral density
Uniform density across the visible wavelength and of no color.
noise
Random pattern of small spots on a digital image that are generally unwanted, caused by non-image-forming electrical signals.
open flash
The technique of leaving the shutter open and triggering the flash one or more times, perhaps from different positions in the scene.
peripheral
An additional hardware device connected to and operated by the computer, such as a drive or printer.
pixel (PICture ELement)
The smallest units of a digital image, pixels are the square screen dots that make up a bitmapped picture. Each pixel carries a specific tone and color.
photoflood bulb
A special tungsten light, usually in a reflective dish, which produces an especially bright (and, if suitably coated, white) light. The bulbs have a limited lifetime.
plugin
In image-editing, software produced by a third party, intended to supplement a program’s features or performance.
power pack
The separate unit in flash lighting systems (other than monoblocks) which provides power to the lights.
ppi (pixels-per-inch)
A measure of resolution for a bitmap image.
processor
A silicon chip containing millions of micro-switches, designed for performing specific functions in a computer or digital camera.
Raw files
A digital image format, known sometimes as the “digital negative,” which preserves higher levels of color depth than traditional 8 bits per channel images. The image can then be adjusted in software—potentially by three stops—without loss of quality. The file also stores camera data including meter readings, aperture settings and more. In fact each camera model creates its own kind of Raw file, though leading models are supported by software like Adobe Photoshop.
resolution
The level of detail in a digital image, measured in pixels (e.g. 1,024 by 768 pixels), or dots-per-inch (in a half-tone image, e.g. 1200 dpi).
RGB (Red, Green, Blue)
The primary colors of the additive model, used in monitors and image-editing programs.
saturation
The purity of a color, going from the lightest tint to the deepest, most saturated tone.
scrim
A light open-weave fabric, used to cover softboxes.
selection
In image-editing, a part of an on-screen image that is chosen and defined by a border in preparation for manipulation or movement.
shadows
The darkest tones of an image.
shutter speed
The time the shutter (or electronic switch) leaves the CCD or film open to light during an exposure.
SLR (Single Lens Reflex)
A camera that transmits the same image via a mirror to the film and viewfinder, ensuring that you get exactly what you see in terms of focus and composition.
split tone
The addition of one or more tones to a monochrome image.
stop
see ƒ-stop. Also used as the action of closing the aperture, as in "to stop down."
TIFF (Tagged Image File Format)
A file format for bitmapped images. It supports CMYK, RGB and grayscale files with alpha channels, and lab, indexed-color, and it can use LZW lossless compression. It is now the most widely used standard for good-resolution digital photographic images.
USB (Universal Serial Bus)
In recent years this has become the standard interface for attaching devices to the computer, from mice and keyboards to printers and cameras. It allows “hot-swapping,” in that devices can be plugged and unplugged while the computer is still switched on.
unsharp mask
A process which increases the apparent detail of an image by computer manipulation.
white balance
A digital camera control used to balance exposure and color settings for artificial lighting types.