1-bit image
An image composed of pixels that are either black or white. Called 1-bit (or single-bit) because only one bit of information is required for each pixel.
24-bit image
An image that uses 24 bits of data for each pixel. Because you can count from 0 to roughly 16-and-a-half million, a pixel can be any one of 16.5 million colors.
32-bit image
An image that uses 24 bits of data to store the color of each pixel and an additional eight bits of data to store the opacity of each pixel. This transparency information is called an alpha channel.
35mm equivalency
What a lens would be equivalent to in terms of a standard 35mm SLR camera. Used as a standard for discussing the field of view and magnification power of a lens. In 35mm equivalency, lenses over 50mm are telephoto, whereas lenses below 50mm are wide-angle or fisheye.
8-bit image
An image that uses eight bits of data for each pixel. Because you can count from 0 to 255, a pixel can be any one of 256 different colors.
Aberrations
Irregularities in a piece of glass that cause light to be focused incorrectly. Aberrations produce artifacts and anomalies in images.
Acquire Plug-in
A special type of plug-in that allows for communication between your image-editing application and your digital camera.
active autofocus
An autofocus mechanism that achieves focus by transmitting something into the scene, usually infrared light or sonar. While active autofocus mechanisms are much more effective in low-light than passive autofocus systems, they have limited range, and don’t work well in situations where there is an obstruction between you and your subject.
Adjustment Layers
In Photoshop, Adjustment Layers let you apply Levels, Curves, and many other image correction functions as a layer, allowing you to remove or adjust the effect at any time.
aliasing
The stair-stepping patterns that can appear along the edges of diagonal lines in an image
alpha channel
Extra information stored about the pixels in an image. Alpha channels are used to store transparency information. This information can serve as a mask for compositing or applying effects.
aperture
An opening that is used to control the amount of light passing through the lens of a camera. Typically constructed as an expanding and contracting iris. The iris is one of three exposure controls that you have on a digital camera, in addition to shutter speed and ISO selection. Each exposure control allows you to affect different image characteristics.
Aperture priority
A shooting mode on a camera. Aperture priority lets you define the camera’s aperture. The camera will then calculate a corresponding shutter speed based on its light metering.
APS
Advanced Photography System. A fairly new format of film and cameras. Most digital SLRs with interchangeable lenses use an image sensor that’s the size of a piece of APS film. Some higher end cameras use a sensor that’s the same size as a piece of 35mm film. Unfortunately, most SLR lenses are designed for 35mm film. As such, when you put one of these lenses on a camera with an APS-sized sensor, the full image provided by the lens gets cropped. This is referred to as a “focal length multiplier” because the cropped size is equivalent to a lens with a longer focal length.
artifacts
Image degradations caused by image-processing operations. Compressing an image, for example, often results in the creation of many image-compression artifacts. Different image-processing tasks create different types of artifacts.
ASA
A measure of film speed. See also ISO.
aspect ratio
The ratio of an image’s length to its width. Most computer screens and digital cameras shoot images that have an aspect ratio of 4:3. 35mm film and some digital cameras shoot in a 3:2 aspect ratio.
aspherical
A lens that contains some elements that are not perfect hemispheres. These nonspherical elements are used to correct certain types of aberrations.
autobracketing
Some cameras include special functions that cause them to automatically shoot a series of bracketed images when you press the shutter release.
autofocus-assist lamp
See focus-assist lamp.
automatic exposure
A feature that will automatically calculate the appropriate shutter speed, aperture, and sometimes ISO at the time you take a picture.
barrel distortion
A type of distortion caused by a lens. Causes the edges of an image to bow outward. Most prevalent in wide-angle and fisheye lenses. See also pincushion distortion.
Bayer pattern
The most common color filter array. A pattern of red, green, and blue filters that can be laid over the photosites of an image sensor and used to calculate the true color of every pixel in the sensor. Because image sensors can only read luminance information, colored filters in combination with complex algorithms must be used to capture full color. The quality of the construction of the filters, as well as the de-mosaicing algorithms (the software that converts the filtered pixels into a full-color image) both affect image quality. De-mosaicing can sometimes lead to aliasing artifacts (the jagged stair-steppy patterns that sometimes appear along high-contrast diagonal lines). However, it’s important not to confuse Bayer pattern artifacts with plain old oversharpening, a much more common problem.
bicubic interpolation
A method of interpolation used in a resampling process. Usually the best interpolation choice when you scale an image.
bilinear interpolation
A method of interpolation used in a resampling process.Photoshop offers a choice of several different interpolation algorithms when resampling an image. When using bilinear interpolation, Photoshop analyzes the pixels to the left and right of each original pixel in the image. A weighted average of the color values of these neighboring pixels is used to determine the color of new pixels. If you’re sampling up, this color is assigned to new pixels that are created to increase the size of your image. If you’re sampling down, this color is assigned to a single pixel that replaces a larger area of pixels, to decrease the size of your image.Bicubic interpolation is a much better choice, as it analyzes all of a target pixel’s neighbors, rather than the pixels on a single axis.
bit depth
A measure of the number of bits stored for each pixel in an image. Images with higher bit depths contain greater numbers of colors. Also known as color depth.
black and white
In the film world, “black and white” is used to refer to images that lack color; that is, images that are composed of only shades of gray. In the digital world, it’s usually better to refer to such images as “grayscale” as because your computer is also capable of creating images composed only of black and white pixels.
blending mode
A setting that determines how the pixels in composited layers blend together. Also known as transfer mode.
blooming
A flaring, smearing artifact in a digital photo caused by a photosite on the camera’s CCD getting overcharged. The extra charge spills into the neighboring photosites and creates the artifact.
boot time
How quickly (or slowly, depending on the camera) the camera will be ready to shoot after powering up.
bracketing
The process of shooting additional frames of an image, each over or underexposed. By intelligently bracketing your shots, you stand a better chance of getting the image you want.
bronzing
If a printer’s black inks have a different reflective quality than their color inks, then a resulting prints will often appear to have variable gloss across its surface. Blacks will look more matte than color areas, and might take on a golden hue. This effect is called bronzing. Some vendors get around this problem by adding an additional “gloss optimizer” which sprays a layer of gloss over the entire image to even out the overal reflectance.
bulb mode
A special shutter mode that opens the shutter for as long as you hold down the shutter release button.
burst
A special mode for shooting a sequence of images in rapid succession. Also known as continuous or burst. The term “drive” is an allusion to the motor-driven drives that are used on film cameras for rapid frame rates.
catchlight
The white highlight that appears in people’s eyes.
CCD
Charge-coupled device, the image sensor used in most digital cameras. For a more-detailed description of how a charge-coupled device works, see Chapter 2 of Complete Digital Photography, 3rd Edition.
center-weight metering
A light metering system similar to matrix metering, but that lends more analytical weight to the center of the image
channel
One component of a color image. Different channels of color are combined to produce a full color image. For example, red, green, and blue channels are combined by your monitor or digital camera to create a full-color picture. Also known as color channel.
chromatic aberrations
Color artifacts caused by the inability of a lens to evenly focus all frequencies of light. Usually appears as colored fringes around high-contrast areas in a scene. See also purple fringing.
chrominance
Color information.
clipping
When highlights or shadows suddenly cut off to completely white or black in an image, rather than fading smoothly.
clone
See Rubber Stamp.
CMOS
Complimentary Metal Oxide Semiconductor. A type of image sensor. Not yet widely used, but offers the promise of better image quality, lower cost, and lower power -consumption than a CCD.
CMS
See color management system.
CMYK
Cyan, magenta, yellow, and black, the primary subtractive colors that are used by a printing process to create all other colors. Although cyan, magenta, and yellow are subtractive primaries, it is impossible to create perfectly pure pigments. Therefore, black ink must be added to create true blacks and darker colors.
coating
Special chemicals applied to a lens that serve to reduce flares and reflection.
color calibration
The process of calibrating your input and output devices, as well as your monitor, so that color is accurately displayed on each.
color channel
See channel.
color depth
See bit depth.
color filter array
The colored filters that are placed over the photosites on an image sensor. Because image sensors can only “see” in grayscale, a color filter array is required for them to capture color information.
color gamut
The range of colors that can be described by a particular color model. Also known as gamut or color space.
color management system (CMS)
A set of software components that work together to compensate for the differences in your monitor, printer, and scanner so that your images appear as accurately as possible on your display.
color matching engine
The software component of a color matching system that performs the translations from one color space to another.
color model
A method of representing color. RGB, CMYK, and L*a*b are all color models and each takes a different approach to representing color. Also see color gamut.
color space
See color gamut.
color temperature
Different lights shine at different temperatures, measured in degrees Kelvin (°K). Each temperature has a different color quality.
CompactFlash
A type of reusable, removable storage. The most common form of storage used in digital cameras.
compositing
The process of layering images on top of each other to create composite images. Compositing is used for everything from creating simple collages to performing complex image correction and adjustment.
continuous autofocus
An autofocus mechanism that constantly refocuses as new objects move into its focusing zone.
contrast detection
An autofocus mechanism that determines focus by measuring contrast in a scene. The mechanism assumes that maximum contrast means sharpest focus. So, it views the scene at different focal lengths, and measures the contrast in each. It can then narrow in on the direction of better contrast and take additional samples to refine focus. Contrast detection is a method of passive autofocus.
contrast filters
Filters that you can add to the end of a lens to increase contrast in an image.
contrast ratios
The ratio of the darkest to lightest tones in an image. The higher the ratio, the more contrast there is in the image.
dark frame subraction
A method of reducing noise in long-exposure digital photos.
demosaicing
The interpolation process that a CCD uses to calculate color. The color of any individual pixel is determined by analyzing the color of the surrounding pixels.
Depth of field
A measure of the area of an image that is in focus. Measured as depth from the focal point of the image.
device profile
A description of the color qualities of a particular device such as a printer, scanner, digital camera, or monitor. Also known as profile or ICC profile.
Digital Negative Specification
An open-source raw format standard proposed by Adobe. Currently, unlike JPEG files, there is no accepted standard for the formatting of raw files from a digital camera. Each camera vendor devises their own standard and usually develops their own software for working with their unique form of raw file. If a third party wants to support that raw format, they must reverse engineer the format and build a custom raw converter. Sometimes camera vendors help with this process, and sometimes they don’t. Adobe’s hope is that camera vendors will adopt their standard, which will make it much easier for third parties to support cameras that use the Digital Negative Spec.For the end user, the main promise of a single raw standard is protection against obsolescence. Currently, there’s no guarantee that your raw format will still be supported years from now, which means you could be left with a bunch of unreadable image data. A single standard would also mean that third party raw conversion software would be able to more-quickly support new cameras.So far, adoption of the Digital Negative Specification by camera vendors has been slow, largely because most camera vendors are not comfortable with a single company (Adobe) controlling the spec. Even though Adobe claims the specification is open source, there’s nothing that would prevent them from changing this in the future.See Adobe’s official Digital Negative Specification page for more details.
Diopter
An optical control that lets you adjust the viewfinder on a camera to compensate for nearsightedness.
Downsample
The process of reducing the size of an image by throwing out data.
drive
A special mode for shooting a sequence of images in rapid succession. Also known as burst or continuous. The term “drive” is an allusion to the motor-driven drives that are used on film cameras for rapid frame rates.
Dual-axis focusing zone
An autofocus mechanism that measures contrast along both horizontal and vertical axes.
Dynamic Range
The range of colors that a device can represent. A digital camera with larger dynamic range can capture and store more colors, resulting in more accurate color images, and more detail in highlights and shadow areas.
Effective pixel count
The actual number of pixels that are used on an image sensor. In many digital cameras, some of the pixels on the camera’s sensor are masked away or ignored.
Electronic TTL Viewfinder
An eyepiece viewfinder that uses a tiny LCD screen instead of normal optics, and that looks through the lens. (This is the same mechanism you’ll find on most video camcorders.)
Element
One individual lens. Most camera lens are composed of many different elements.
Emulsion
The light-sensitive chemical coating on the surface of a piece of film.
EXIF
Exchangeable Image File. A digital image file format used by most digital cameras. Notable because it includes special header information where all of an image’s parameters (shutter speed, aperture, etc.) are stored.
Exposure
The combination of aperture, shutter speed, and ISO settings that determine how much light will be recorded at the focal plane.
Exposure Compensation
A mechanism for adjusting the exposure on your camera that is independent of any particular exposure parameter. In other words, rather than specifically changing the aperture or shutter speed, you can simply use exposure compensation to over or underexpose an image. The camera will calculate the best way to achieve the compensation.
Exposure Lock
A mechanism that lets you lock the exposure on your camera independently of focus.
External flash sync
Alows you to connect an external flash (usually a specific model) to the camera using a small cable.
Falloff
How quickly an effect changes. For example, a depth of field blur may have a quick falloff, meaning it the blur goes from sharp to blurry very quickly.
Fast shutter mode
Forces a large aperture to facilitate a fast shutter speed. Sometimes calledsports mode.
Feather
The process of blurring the edge of a selection to create a smoother blend between an edit and the rest of an image.
Fill flash
Allows you to force the flash to fire to provide a slight fill light. Also known as force flash.
Film
A quaint, 19th-century analog technology for recording images. Requires lots of hazardous chemicals, a lot of patience, and doesn’t offer cool features like Levels dialog boxes or Rubber Stamp tools. Not for the impatient. Does have the advantage that the recording and storage mediums are included in the same package.
Filter factor
Most lens filters are documented with a filter factor which will inform you of the exposure compensation (in stops) required when you use that filter.
Filters
Either colored plastics or glass that you can attach to the end of your camera’s lens to achieve certain effects, or special effects that you can apply to your image in your image editing program (see plug-ins).
Firewire
A type of serial connection provided by many computers and digital cameras. Can be used for transferring images between camera and computer. Much faster than USB. Also called IEEE-1394 or i.Link.
Fisheye
An extremely wide-angle lens that creates spherical views.
Flash compensation
A control that allows you to increase or decrease the intensity of your camera’s flash. Usually measured in stops.
Flash memory
A form of non-volatile, erasable memory. Used in digital cameras in the form of special memory cards.
Focal length
The distance, usually measured in millimeters, between the lens and the focal plane in a camera.
Focal length multiplier
Many digital SLRs use an image sensor that is smaller than a piece of 35mm film. If you attach a lens to one of these cameras, its 35mm equivalency will be multiplied by the focal length multiplier. For example, if your digital SLR has a focal length multiplier of 1.6x, then a 50mm lens mounted on your camera will have an effective focal length of 80mm.
Focal plane
The point onto which a camera focuses an image. In a film camera, there is a piece of film sitting on the focal plane. In a digital camera, a CCD sits on the focal plane.
Focus assist lamp
A small lamp on the front of the camera that the camera can use to assist autofocusing. Also known as autofocus assist lamp.
Focus ring
The ring on a lens that allows you to manually focus the lens. Most smaller digital cameras lack focus rings, which can make them difficult to manually focus.
Focus tracking
An autofocus mode provided by some cameras that can track a moving object within the frame and keep it in focus. Sometimes called Servo focus.
Focusing spot
See focusing zone
Focusing zone
An area in the camera’s field of view in which the camera can measure focus. Most cameras only have one focusing zone. The camera will focus on the object in this zone. Some cameras have multiple zones.
Force flash
See fill flash.
Full frame sensor
An image sensor that’s the same size as a piece of 35mm film. This is in contrast to a “cropped” sensor which typically has the same dimensions as a piece of APS film. Larger sensors can yield shallower depth of field, and offer larger pixels, which can produce images with less noise.
Gamma
The mid-point (between black and white) in a tonal range.
Gamut
See color gamut.
Gels
Thin pieces of plastic that are usually placed in front of lights to create colored lighting effects.
Gigapixel
Dream on.
Grayscale
An image composed entirely of shades of gray, rather than color. (Basically a fancy name for “black and white.”)
Group
Multiple elements cemented together in a lens.
Halftoning
A process used for printing photos that begins by shooting a photo of an image through a special halftone screen. The resulting photo gets broken down by the screen into a pattern of dots that can be easily printed using a single ink. Your computer can generate halftone output from a laser printer, allowing you to skip the photographic halftoning step.
Hardware calibration
Special devices that measure the color of an output device. The data gathered by the device is then used to create a color profile of the device. This profile is, in turn, used by color management software to ensure accurate color output.
Histogram
A graph of the distribution of tones within an image. The histogram is one of the most powerful tools that you have for image correction and shooting (assuming your camera has a built-in histogram feature). With an on-board histogram you can perform a much-better assessment of your exposure and ensure that you’re capturing a full range of good data, which will make your editing tasks easier. An on-board histogram is one of the tools that gives the digital photographer an edge over their film counterparts, when shooting.
Hot shoe
A mount for attaching an external flash to a camera.
Hot shoe
A mount for attaching an external flash to a camera.
i.Link
Sony’s name for firewire.
ICC profiles
See device profile.
IEEE-1394
The official name for firewire.
Image buffering
The ability of a camera to temporarily store images in an internal memory buffer before writing them out to a memory card. A large image buffer facilitates the rapid shooting of multiple frames as the camera doesn’t have to stop shooting to offload images to storage.
Image stabilization
Some telephoto camera lenses offer special optics that can stabilize the tiny shakes and jitters that can be caused by your hand.
Interpolation
The process of calculating missing data in an image based on data that is already there.
Intervalometer
A piece of hardware or software that controls your camera and triggers an exposure at regular intervals, to create time-lapse effects. Some cameras have intervalometers built in. If yours doesn’t, then you might be able to add this functionality through an external remote, or by tethering your camera to a computer and running special software. Most intervalometers let you control the interval between shots, how many shots to take, and how many shots to take at each exposure.
Iris
A mechanism of interlocking, sliding metal blades that can expand and contract to create circular apertures to control the amount of light passing through a lens. The iris on a camera is used to control the aperture.
ISO
In film photography, a measure of a film’s “speed” or light sensitivity. The higher the ISO, the more sensitive the film. The sensitivity of digital camera sensors are also rated using the ISO scale. ISO stands for the International Organization for Standardization (or, International Standards Organization, if you want an acronym that fits better) the people who define, among many other things, the spec used to gauge light sensitivity. ISO is equivalent to the old ASA scale (American Standards Association) which has since been discontinued. (Curiously, ISO is not meant to be an acronym for anything, it’s allegedly a pun on the Greek prefix “iso-” meaning “same.”)
ISO is one of three exposure controls that you have on a digital camera, in addition to aperture and shutter speed selection. Each exposure control allows you to affect different image characteristics.
JPEG
Joint Photographic Experts Group. More commonly, the name of a popular lossy image compression scheme.
L-Ion
Lithium Ion. A type of rechargeable battery.
L*A*B Color
A color model created by the Commission Internationale de l’clairage. Lab color describes colors as they actually appear, rather than by how they are made. As such, Lab color makes a great reference space for performing color management and calibration.
Lab color
A color model created by the Commission Internationale de l’clairage. Lab color describes colors as they actually appear, rather than by how they are made. As such, Lab color makes a great reference space for performing color management and calibration.
Latitude
How far colors in an image can be pushed or pulled.
Lens flares
Bright color artifacts produced in a lens by reflections within the lens itself.
Line screen frequency
The density of the screen that is used in a halftoning process. A screen with more density yields an image with smoother tones and more detail.
Linear array
A digital camera mechanism that uses a single row of sensors that makes three separate filtered passes over the imaging sensors to create a full-color image.
Live View
In a digital SLR, a feature that allows you to use the LCD display as a viewfinder. Because the mirror in the camera must be flipped out of the way during live view, not all cameras are able to use their autofocus mechanism while live viewing. Different vendors offer different work arounds from temporarily flipping the mirror back down for a quick autofocus, to analyzing the image detail on the sensor and using a contrast-detection algorithm to calculate focus, to using a second focus meter near the image sensor.
Lossless
Indicates that a particular process does not result in any loss of quality.
Lossy
Indicates that a particular process results in loss of quality.
Luminance
Brightness information.
Macro
A special type of lens used for photographing objects at extremely close distances.
Manual mode
A shooting mode on a camera that allows you to set both the aperture and shutter speed, giving you full control over the camera’s exposure.
Matrix meter
A light meter that analyzes many different areas of your scene to determine proper exposure.
Megapixel
A million pixels. Usually used as a measure of the resolution of a digital camera’s sensor.
Metering
The process of measuring light with a light meter (or by eye) so as to determine proper exposure for a shot.
Mirror lock-up
The ability to lock a camera’s mirror into the “up” position to reduce vibration when shooting long exposure images. Some higher-end cameras also provide a lock-up feature to aid in cleaning the camera’s sensor.
Multi-segment meter
See matrix meter.
Multi-spot focus
An autofocus mechanism on a camera that can focus on one of several different places within an image.
Multiple array
A digital camera mechanism that uses three separate CCDs for capturing a color image, one each for red, green, and blue.
Nearest neighbor
A method of interpolation used in a resampling process.
Neutral density filter
A filter that cuts down on the light entering your camera’s lens, without altering the color of the light. Enables you to use wider apertures or faster shutter speeds in bright light.
NiCad
Nickel Cadmium. A type of rechargeable battery. Not recommended for use in a digital camera. NiCad’s won’t hurt your camera, but they won’t last very long, and they have a tendency to develop a “memory” effect that prevents them from attaining a full charge.
NiMH
Nickel Metal Hydride. A type of rechargeable battery.
Nodal point
The optical center of a camera’s lens.
Noise Reduction Software
The bane of all digital photographers. Noise appears in an image as very fine-grained patterns of multi-colored pixels in an area. Shadow areas are particularly susceptible to noise as are images shot in low-light. Noise is very different-looking than the grain found in film photos. Unfortunately, it’s also far less attractive.
Normal lens
A lens that has a field of view that is equivalent to the field of view of the human eye. Roughly 50 mm (in 35mm equivalency).
Overexposed
An image that was exposed for too long. As an image becomes more overexposed it gets brighter and brighter. Highlights and light-colored areas wash out to completely white.
Parallax
The easiest way to understand parallax is simply to hold your index finger in front of your face and close one eye. Now close the other eye and you’ll perceive that your finger has jumped sideways. As you can see, at close distances, even a change of view as small as the distance between your eyes can create a very different perspective on your subject. A camera that uses one lens for framing and another for shooting faces the same problems. Parallax is not a problem at longer ranges as the parallax shift is imperceptible.
Passive autofocus
An autofocus mechanism that achieves focus by analyzing the camera’s view of the scene, as opposed to an active autofocus mechanism which uses a separate sensor to measure focus. Most passive autofocus mechanisms use a contrast detection system for measuring focus, while most active-autofocus mechanisms use an infrared beam.
PC Card Adapter
A special adapter that lets you insert a storage card from your camera into the PC card slot of your computer.
PC Cards
Small, credit-card-sized peripheral cards that can be inserted into a PC Card slot on a laptop computer, or into a special PC Card drive on a desktop computer. PC Card adapters are available for most kinds of digital camera media, allowing you to insert media directly into your PC Card slot.
Phase difference
An autofocus mechanism that uses measurements taken through different parts of the camera’s lens to determine focus. Also known as phase detection.
Photosite
A tiny electrode that sits on the surface of an image sensor. There is one photosite for each pixel on a sensor.
Pincushion distortion
A type of distortion caused by a lens. Causes the edges of an image to bow inward. Most prevalent in telephoto lenses. See also barrel distortion.
Pixellate
Sometimes, the individual pixels in an image can become visible, a process called pixellation.
Plug-ins
Special bits of code – usually effects or image processing filters – that can be added to your image editing application. Most plug-ins conform to the Photoshop plug-in standard.
Polarization
Special filters that can be fitted onto the end of a lens. Polarizers only allow light that is polarized in a particular direction to enter your lens. Polarizers can completely remove distracting reflections from water, glass, or other shiny surfaces. Polarizers can also be used to increase the contrast in skies and clouds.
Posterization
Reduction of the number of tones in an image. As a particular tonal range gets posterized, it will appear more “flat.”
PPI
Pixels per Inch, a measure of resolution.
Prefocus time
How long it takes a camera to perform its prefocus steps (autofocus, metering, and white balance).
Prefocus time
The process of autofocusing, metering, and white balancing that occurs when you press your camera’s shutter release button halfway.
Prime lens
A lens with a fixed focal length. (Technically, a “prime” lens is simply the first lens that serves to focus light toward the focal plane. As such, you’ll often find camera vendors using the term “fixed focus lens” in place of “prime lens.” They’re just being all engineery and precise, which is fine. The more common, popular use of the term,though, is the one shown here. It is used to differentiate this type of lens from a zoom lens.)
Priority Mode
A mode on a camera that allows you to set a specific exposure parameter. The camera then calculates the other exposure parameters accordingly. For example, in Shutter Priority mode, you select the shutter speed you want, and the camera picks a corresponding aperture, based on its metering of the scene (if your camera also has auto ISO, then ISO might be adjusted as well). Aperture priority allows you to specify an aperture. The camera will pick an appropriate shutter speed upon metering.
Program Shift
Program Shift allows you select specific aperture and shutter speed combinations when you’re in a fully-automatic Program mode. Program shift features usually work like this: in Program mode, press the shutter button halfway to meter and lock focus. Now, adjust the Program shift control. The camera will automatically cycle through all reciprocal shutter speed/aperture combinations for that particular exposure. So, you end up with the same level of exposure, but you can choose between a shutter speed/aperture combo that has a faster or slower shutter speed, or larger or smaller aperture. Program shift gives you a great degree of manual control, even when you’re in a fully automatic program mode. Consult your camera manual for details.
Proportional zoom control
A zoom control whose rate of zoom changes depending on how far you push or pull the control.
Prosumer
A marketing term for a camera that sits somewhere between the professional and consumer market.
Purple fringing
A color artifact specific to digital cameras with resolutions greater than two megapixels. Appears in an image around the edges of high-contrast objects, usually shot with wide-angle lenses. Usually confined to the edges of the screen. See also chromatic aberrations.
Quantization
In JPEG compression, the process of averaging the colors in one 64-pixel square area.
Quantizing
The process of assigning a numeric value to a sample. Part of the digitizing process.
Raw data
Pixel data that comes directly from the CCD with no further processing. Processing is usually performed later using special software. Raw files offer quality equivalent to an uncompressed image, but require much less space.
Raw file
Pixel data that comes directly from the CCD with no further processing. Processing is usually performed later using special software. Raw files offer quality equivalent to an uncompressed image, but require much less space.
Reciprocity
Exposure parameters have a reciprocal relationship so that different combinations of parameters produce the same exposure. For example, setting your camera to a shutter speed of 1/250th of a second at f8 is the same as setting it to 1/125th at f16.
Rectilinear
A type of wide-angle lens that includes corrective elements that prevent barrel distortion.
Recycling
The time it takes a camera to reset itself and prepare to shoot another shot.
Red eye reduction
A special flash mode that attempts to prevent red eye by firing a short initial flash to close down the irises in your subject’s eyes.
Red-eye
When the flash from a camera bounces off a subject’s eyes and back into the camera’s lens, the subject will appear to have bright red eyes. Most prevalent in cameras where the flash is very close to the lens.
Refraction
The process of slowing and bending light using a transparent substance such as air, water, glass, or plastic.
Refresh Rate
How often the image on a camera’s LCD viewfinder is redrawn. An LCD with a higher refresh rate will produce an image with smoother motion.
Resampling
The process of computing new pixel information when resizing a document in your image editing application. If you are resizing upward, then the resampling process will generate new pixels. If you are resizing downward, then the resampling process will discard pixels.
resampling
Resampling is the process of computing new pixel information to scale an image to a larger or smaller size. Photoshop offers a choice of several algorithms for computing new pixels when resampling. Bicubic is the best choice for almost all images.
Resolution
In a monitor or digital camera, the number of pixels that fit into a given space. Usually measured in pixels per inch (ppi) or dots per inch (dpi). In a printer, the number of printer dots that fit into a given space, usually measured in dots per inch (dpi).
RGB
Red, green, and blue, the additive primary colors of light that are used by your computer monitor and digital camera to produce all other colors.
Rubber Stamp
An image editing tool that works like a paint brush, but that copies image data from one part of your image to another. A staple retouching tool. Sometimes called a clone tool.
Sampling
The process of analyzing something to determine its content. A digital camera samples light to determine how much, and what color the light is, at any given point in a scene.
Saturation
A characteristic of color. Colors that are more saturated are typically “deeper” in hue and often darker. As saturation increases, hue shifts slightly.
Servo focus
An autofocus mode provided by some cameras that can track a moving object within the frame and keep it in focus. Sometimes called Servo focus.
Sharpening
The process of using software to increase sharpness in a digital image. Sharpening can happen inside a digital camera or through post-processing on your computer.
Shutter
A mechanism that sits in front of the focal plane in a camera and that can open and close to expose the image sensor or film to light. Many digital cameras do not have physical shutters, but instead mimic shutter functionality by simply activating and deactivating their image sensors to record an image. Cameras that do have shutters typically use a two-curtain mechanism. The first curtain begins to slide across the focal plane to create a gap. It is followed – usually very quickly – by a second shutter that closes the gap. As the gap passes across, the entire sensor is exposed.
Shutter lag
A delay between the time you press the shutter release button on a camera, and the time it actually shoots a picture.
Shutter priority
A shooting mode on a camera. Shutter priority lets you define the camera’s shutter speed. The camera will then calculate a corresponding aperture based on its light metering.
Shutter speed
The length of time that it takes for the shutter in a camera to completely open and close. Shutter speed is one of three exposure controls that you have on a digital camera, in addition to aperture and ISO selection. Each exposure control allows you to affect different image characteristics.
Single array system
A digital camera mechanism that uses a single image sensor for imaging. Sometimes called a “striped array.”
Single lens reflex
A camera whose viewfinder looks through the same lens that your camera uses to make its exposure. Also known as SLR.
Single-axis focusing zone
An autofocus mechanism that measures contrast along a single axis only, usually horizontal.
Slow sync mode
A special flash mode that combines a flash with a slow shutter speed to create images that contain both still and motion-blurred objects.
SLR
A camera whose viewfinder looks through the same lens that your camera uses to make its exposure. Also known as SLR.
SmartMedia
A type of reusable, removable storage.
Soft proof
An on-screen proof of a color document.
Specular highlights
The bright white glints and reflections that occur on very shiny surfaces and on the edges of objects.
Spot meter
A light meter that measures a very narrow circle of the scene.
sRGB
An RGB color space defined by Microsoft and Hewlett Packard. It is intended to represent the colors available on a typical color monitor. A little too small for digital photography work.
Step-up ring
An adapter that attaches to the end of a lens and allows for the addition of filters or other lens-attachments. Serves to change the thread size of the lens.
Stitching
The process of joining and blending individual images to create a panoramic image.
Stop
A measure of the light that is passing through a camera’s lens to the focal plane. Every doubling of light – either through changes in aperture, shutter speed, or ISO – is one stop. See also f-stop.
Subtractive
Ink mixes together in a subtractive process whereby as colors are mixed together they get darker – that is, light is subtracted as the colors are mixed. Subtractive colors eventually produce black. Cyan, magenta, and yellow are the primary subtractive colors that can be used to create all other colors.
Telephoto
A lens with a focal length that is longer than normal. As a lens gets more telephoto, its field of view decreases.
TFT
A technology used to create LCD screens. Typically used for the LCD viewfinder/monitors included on the backs of many digital cameras.
Thin film transistor
A technology used to create LCD screens. Typically used for the LCD viewfinder/monitors included on the backs of many digital cameras.
Three-shot array
A digital camera mechanism that uses three single arrays, one each for red, green, and blue.
Through the lens
A viewfinder mechanism that looks through the same lens that is used to focus the image onto the focal plane. Short for through the lens.
Transfer mode
A setting that determines how the pixels in composited layers blend together. Also known as blending mode.
Trilinear array
A digital camera mechanism that uses three linear arrays stacked on top of each other to create a full-color image in a single pass over the image sensor.
TTL
A viewfinder mechanism that looks through the same lens that is used to focus the image onto the focal plane. Short for through the lens.
Underexposed
An image that was not exposed enough. In an underexposed image, dark, shadow areas turn to completely black.
Upsample
The process of enlarging an image by calculating (interpolating) new data.
USB
Stands for Universal Serial Bus. A type of serial connection provided by many computers and digital cameras. Can be used for transferring images between camera and computer.
VGA Resolution
640 x 480 pixels.
Video LUT Animation
A feature available in some versions of Photoshop that allows for real-time, on-screen viewing of color corrections and changes.
Video RAM
The memory in a computer that is used for displaying images on-screen. The more video RAM, the larger your images can be, and the greater the bit depth they can have. Also known as VRAM.
Vignetting
A darkening of the image around the edges.
Wavelet compression
A new fractal-based compression scheme. Converts your image from a series of raster dots into a collection of tiny fractal curves.
White balance
A color calibration used by a camera. Once a camera knows how to accurately represent white it can represent all other colors. Because white can look different under different types of light, a camera needs to be told what white is, a process called white balancing.
Wide-angle
A lens with a focal length that is shorter than normal. As a lens gets more wide-angle, its field of view increases.
Zone system
A method of calculating exposure.
Zoom lens
A lens with a variable focal length.