Compiled by Sonny Saunders
The following are important words to know and understand as you explore digital photography.
Aberration: Essentially, anything in an image that is not supposed to be there. For example, optical imperfections within a lens may cause distortions such as barrel distortion or pincushioning.
Active Auto Focus System: Active autofocus cameras bounce infrared beams off the subject to determine the distance.
ADC (Analog-to-Digital Converter): A processor used to convert continuous varying (analog) signals into a set of digital values.
AD Converter: see Analog-to-Digital Converter
Additive Primary Colors: The red, green and blue hues used to create all other colors.
Adobe RGB: The color space licensed by Adobe and used by digital camera companies. This is an expanded color space used for commercial and professional printing.
Adobe RGB (1998): The color space licensed by Adobe and used in early digital cameras. This color space is formatted for computers application workspace.
Adobe DNG: Digital Negative (DNG) is an open raw image format owned by Adobe for digital photography.It is offered as a universal raw format. Launched on September 27 2004. All Adobe photo manipulation software (such as Adobe Photoshop and Adobe Lightroom) released since the launch supports DNG.
Adobe DNG MD-5 checksum:Unique validation checksum generated from data of the original raw capture, that can be used by a number of applications to determine the validity of the critical bits of the file’s data.
AEB: Automatic exposure bracketing, which takes a series of pictures at different exposures.
Algorithm: An effective method of solving a problem using a finite sequence of instructions.
A-TTL: Advanced through the lens flash metering sends out a brief burst of light, for metering, when the shutter button is depressed half-way. This preflash is recorded by an external sensor on the front of the flash and used to determine a reasonable aperture to ensure adequate depth of field, particularly at short distances. The flash unit then sends out the actual scene-illuminating flash once the shutter has opened. This type of flash metering has been replaced by E-TTL.
Ambient light: Existing light found in a scene.
Analog-to-Digital Converter: A processor used to convert continuous varying (analog) signals into a set of digital values.
Angle of view: The area of a scene that the lens can capture, expressed as an angle, and reproduced as a sharp image. Lenses with shorter focal length have a wider angle of view than lenses with a longer focal length.
Anti-aliasing: Using software to soften and blend rough edges (called aliased).
Aperture: Measured in f-stop numbers, it is the variable opening in a lens that controls the amount of light that hits the image sensor, thereby affecting exposure. A small f-stop number (i.e., f/2.8) represents a wide lens opening, which allows more light to pass through the lens to the sensor and is beneficial in low-light conditions. A larger f-stop number (i.e., f/8.0) narrows the lens opening and allows less light to hit the sensor. The latter provides a broader depth of field, while the former decreases the depth of field.
APO (Apochromatic): Lenses that use internal elements to bring all colors of the visible spectrum to a common point of focus, creating a sharp image and minimizing chromatic aberrations, are referred to as APO lenses. These lenses are generally more expensive than non-APO lenses.
Aperture Priority: A shooting mode on a camera. Aperture priority lets the photographer define the camera’s aperture or f-stop. The camera will then calculate a corresponding shutter speed based on its light metering.
Apochromatic Lens: A lens that incorporates an ultra-low dispersion glass element used to control color fringing or chromatic aberrations. These lenses carry a special designation: Canon and Tamron (LD), Nikon (ED), Sigma (ELD) and Tokina (SD).
Archival storage: Using external, non-magnetic media such as CDs for the long-term storage of information.
Artifact: Anything that occurs in a photograph from technology and not from the scene itself. This can be unwanted noise found in an image caused by JPEG compression or the limitations in the recording process.
Aspect Ratio: The aspect ratio of a camera is the ratio of the length of the sides of the image produced. A traditional 35mm film frame is approximately 36mm wide by 24mm high. This is an aspect ratio of 36:24, which is expressed as a 3:2 ratio. Most non D-SLR digital cameras have an aspect ratio of 4:3 while most D-SLR’s have the 3:2 ratio. Typically video monitors have a 4:3 aspect ratio with a 800×600 display.
Aspheric Lens: Lens elements that are not sphere-shaped. Instead of having an arc-shaped concave or convex front or back surface they are not sphere-shaped. Most aspheric lenses are hybrids of a molded plastic lens element cemented onto a aspheric glass lens. These lenses elements are usually used to control aberrations or distortions in ultra-wide angle and large-aperture lenses.
Autofocus: The ability of the camera to focus its lens automatically. There are two types of autofocus; Active and Passive and Continuous.
Back Light: Light produced when the sun or light source is in front of the camera. This type of lighting produces theatrical results for subjects with a distinctive forms or translucent properties.
Banding: Loss of image quality caused by expanding the tonal range of an image during post processing. Primarily occurs when expanding underexposed images. Occurs most often with JPEG images as they have less tonal information, but can also occur with RAW images.
Bicubic: Image interpolation that calculates the value of a new pixel based on 16 pixels from the nearest 4×4 pixel grid in the original image.
Bicubic Sharping: Sharping based on Bicubic Interpolation.
Bicubic Smoothing: Smoothing based on Bicubic Interpolation
Bilinear: Image interpolation that calculates the value of a new pixel based on the average of the nearest four pixels in the original image
Bit: The smallest data unit of binary computing, being either 1 or 0. Eight bits make up one byte.
Bit-Depth: Also referred to as color depth, bit-depth determines the maximum number of shades or intensities of colors that can be represented at a time. Camera sensors typically have 12-bits-per-channel color (red, green and blue) for a 36-bit image (which JPEG compression reduces to 8 bits per channel). Although more bit-depth is preferable, there are diminishing returns beyond 8 bits per channel (8 bits x 3 channels = 24 bit-depth). Image file sizes increase dramatically, and not all devices (printers, monitors) will benefit from higher bit-depth. Additionally, some image editing may have limited—or no—capabilities of working beyond 8 bits.
Bokeh: The aesthetic qualities of the out-of-focus parts of an image, and whether the out-of-focus points of light, circles of confusion, are distracting fuzzy disc, or if they smoothly fade into the background. Bokeh can vary from lens to lens or within a given lens at different aperture settings.
Byte: A packet of information that consists of 8 bits. Computers typically have 8-bit data pathways, making bytes the most efficient means of transmitting data or instructions.
CCD (Charge-Coupled Device): A common type of image sensor used in digital cameras. The CCD actually only sees black & white images and must have red, green, and blue filters built into it in order to capture color. CCD sensors use more power and are slower than CMOS type sensors
CD-R, CD-RW: These are compact disk formats for storing data, and work very well for photographs. The “r” in CD- R stands for recordable, and this disk can be recorded onto once. The “rw” in CD- RW stands for rewritable, and this disk can be recorded, erased, and then reused by recording onto it again.
CD-ROM (CD-Read-Only Memory): A compact disk that contains information that can only be read not updated or recorded over.
Chip: Common term for a computer-integrated circuit, a key part of a computer.
Chroma: The existence of color in an image.
CIPA: Camera and Imaging Products Association has set standard on how the number of pixels in a camera should be counted. It does all kind of camera testing.
Chromatic Aberration: Color fringing caused when a lens does not focus all colors at the same focal point or on the same focal plane. While a chromatic aberration can be purple, the term “purple fringing”—a purple/blue fringe along high-contrast edges—refers to a separate phenomenon that is generally caused by characteristics of the sensor.
Circular Polarizer: Digital cameras require the use of a circular polarizer, as opposed to a linier polarizer filter, in order for the auto-focus to operate properly. A circular polarizer filter is essentially a linear polarizer with another optical element added. It mixes the light so it isn’t polarized, but it does it after the light has already passed through the polarizing element and gotten rid of the glare, reflections and other artifacts that you use a polarizing filter for.
CMOS: (Complementary Metal Oxide Semi-Conductor) This image sensor is used in several digital cameras. CMOS sensors use less energy and are much faster operating than CCD sensors. Since these sensors are manufactured on a far less expensive platform and are easier to produce they are more cost-effect.
CMYK (Cyan, Magenta, Yellow, Black): These are the subtractive primary colors. They’re used in so called four-color printing processes used in booklets and magazines because they produce the most photo-realistic look for publications.
Color Gamut: In color reproduction, including photography the gamut, or color gamut is a certain complete subset of colors. The concept is easy: Imagine a crayon box in several different sizes, ranging from 10 different crayons to a large box with 16.7 million different color crayons. A 24-bit color image can have up to 16.7 million different shades of color.
Color Management: In digital imaging systems, color management is the controlled conversion between the color representations of various devices, such as image scanners, digital cameras, monitors, TV screens, printers, computers, offset presses, and corresponding media. The primary goal of color management is to obtain a good match across color devices. Color management take into account the differences between different device color spaces (gamuts) as it makes corrections.
Color Profile: In general color profiles are used to correct colors of each of the devices used in developing and printing an image. Each devise will have its own color profile and a color management system will use these profiles to give the correct color at the end of the process.
Color Space: Every device that produces, measures, or captures color has its own way of reproducing all the colors in the visible spectrum, which is known as its color space. The most common color spaces in digital photography are Adobe RGB and (Adobe) sRGB. The former has a broader color gamut (range of colors/tones), while sRGB has a smaller color gamut.
Color Temperature: Different lights shine at different temperatures, measured in degrees Kelvin (K). Each temperature has a different color quality.
CompactFlash®: The most widely used reusable removable photographic image storage device in use.
Compression: The process of encoding files through an algorithm, which decreases the size for storage or transmission over the Internet. There are two types of compression: lossy and lossless. Lossy compression (JPEG is an example) can result in visible degradation of image quality, especially when saving the same image as a JPEG multiple times, because some image data is lost in each compression process. Lossless compression (like LZW compression) preserves all image data.
Continuous Focus: The camera continually focuses on a subject. This works best on moving subjects.
Continuous Tone (CT): The appearance of smooth color or black & white gradations, as in a photograph.
Copyright: A legal term that denotes rights of owner-ship and, thus, control over usage of written or other creative material. Unless otherwise noted, assume all images are copyrighted and can’t be used by anyone without permission of the photographer.
CPU (Central Processing Unit): The “brain” of a computer system.
Data compression: the use of algorithms to reduce the amount of data needed to reconstruct a file.
Depth of Field: The dept of field is the zone of apparent sharpness in a photo in front of and beyond the focused subject. A measure of the area of an image that is in focus. The dept of field is always proportioned 1/3 in front of the camera focus point and 2/3 to the rear of the camera focus point.
Diffraction: The tendency of light to change intensity and direction when going around a barrier like and aperture. Diffraction causes softness in an image, and diffraction limits the f-stops that a compact digital camera can have (not over f/8, and f/8 equals f/32). The depth of field at a particular f-stop can produce is inversely proportional to the size of the sensor.
Digital zoom: An over-hyped feature of digital cameras that takes a portion of the sensor’s active area and digitally enlarges it to achieve the appearance, though not the quality, of a telephoto zoom lens. Digital zoom should only be used as a last resource.
DL: Dual layer recordable DVD
Dot pitch: Typically used to evaluate a monitor’s sharpness as a measurement of the distance between dots; A smaller number indicates a sharper monitor.
DPI (Dots per Inch): (Not a camera function.): measures the number of drops of ink (per inch) a printer lays down on a piece of paper. Generally, selecting higher dpi settings will result in a smoother transition from color to color with more visible detail.
Drum scanner: A specialized scanner commonly used by the printing industry for very high-quality scans. It’s very expensive and has a steep learning curve.
D-SLR: Modern D-SLRs are digital cameras based on the same mechanical and optical features of film SLR (single lens reflex) cameras, minus the film. SLR cameras channel light through a lens and a mirror to a viewfinder that gives an exact preview of the shot to be captured.
DVD-R: A write-once format. Good for archiving data and recording data and images. Compatible with about 85 percent of all drives. This format is becoming the most common used.
DVD+R: A write once format. Good for archiving data and recording data and images. Compatible with about 85 percent of all drives.
DVD+RW: Alliance’s DVD+RW drive offers a 1000 times-rewriteable format. Excellent for backing up. Compatible with about 65 percent of all drives.
DVD-RW: Forum’s DVD-RW drive offers a 1000 times-rewriteable format. Suitable for backing up. In most burners it writes a half the speed of DVD+RW. Compatible with about 65 percent of all drives.
DVD-RAM: Forum’s DVD-RAM drive offers a 100,000 times-rewriteable format. Suitable for backing up, much slower than DVD-RW and DVD+RW. Compatible with few drivers.
DVD9: Dual layer recordable DVD
Dynamic Range: The difference between the highest and the lowest values in an image, as in the brightest highlights and the darkest shadows. Also known as ‘Brightness Range’. The range of tones, from lightest to darkest, that can be recorded, displayed or reproduced by devices such as image sensors, scanners, printers and monitors.
ED, LD and UD Glass: (Low-Dispersion, Extra-Low-Dispersion and Ultra-Low-Dispersion Glass) All these terms refer to a glass type used in lenses. These formulated glasses correct the path of light rays as they pass through the lens, making all colors in the color spectrum focus at the same point. Lenses constructed with these types of glass eliminate or lessen the occurrence of aberrations and some types of artifacts.
EEPROM: Electrically erasable programmable read-only memory, also called Flash Memory. Digital camera memory cards consist of several flash memory chips and a controller. The controller’s on-board software manages the writing and erasing of data and determines the memory card speed.
Effective Pixels: Pixels on the sensor actually used to capture an image. Often, not all the pixels on a sensor can be used to capture the image, but are used for other functions.
Exposure: A controlled amount of light projected to an image sensor or frame of film.
EXIF: Exchangeable Image File standard was established in 1995 as a way to accommodate a range of image file formats and allow photos made with one kind of camera to be played and viewed on another, different device. In addition to image data, the next most important feature of EXIF is its inclusion of thumbnails. Adobe Photoshop Elements make use of EXIF data to display thumbnails in its image management mode. Opanda PowerExif is a Windows-based software tool that can be used to edit the EXIF data in image files. Here is a list (in alphabetical order) of camera companies that officially support EXIF Print: Canon, Casio, Fujifilm, Kodak, Nikon, Olympus, Panasonic, Pentax,
Ricoh, Sanyo and Sony.
EXIF 2.2: (aka EXIF Print) records all of the information set by the photographer. The printer reads all of this photographic information to ensure optimal printing including capture parameters and scene information in the form of EXIF tags.
EVF: Electronic ViewFinder An eyepiece viewfinder that uses a tiny LCD screen instead of normal optics, and that looks through the lens.
EVIL: See ILDC (Interchangeable Lens Digital Camera)
E-TTL: Evaluative through the lens flash metering. E-TTL fires a low-power preflash of known brightness from the main bulb to determine correct flash exposure. It measures the reflectance of the scene with the preflash, then calculates proper flash output to achieve a midtoned subject, based on that data. The E-TTL preflash occurs immediately before the shutter opens.
E-TTL II: Evaluative through the lens flash metering introduced by Canon in 2004 is an improved version of regular E-TTL. E-TTL II examines all evaluative metering zones both before and after the E-TTL preflash goes off. Those areas with relatively small changes in brightness are then weighted for flash metering. This is done to avoid the common E-TTL problem of highly reflective materials causing secular highlights in a flash-illuminated image and throwing off the flash metering. Normally E-TTL II uses evaluative algorithms for its flash metering, but this system can also receive distance information from the lens in used.
Exposure: The combination of aperture, shutter speed and ISO settings that determine how much light will be recorded at the focal plane.
Extension Tubes: Are hollow spacers that mount between the camera body
and the lens, extending the distance from the lens to the camera sensor,
causing the lens to focus much closer than normal. The longer the extension
tube(s), the closer the attached camera lens can focus
Exif (Exchangeable Image File Format): EXIF information is generated by the digital camera and contains information about various camera settings. Data such as when a picture was taken (provided the camera’s settings are accurate), aperture, shutter speed, lens mm setting, camera model and more is stored with JPG and TIFF images. There isn’t a standard format for RAW files; however, manufacturers have created their own formats.
FAT: File Allocation Table
Feathering: Softening the edges of elements in an image by blending the effect across the edge.
FFT-CCD: is a Progressive scan sensor producing higher image quality than is found with many equal or higher megapixel CCD models. Unique to the Olympus SLR’s, the FFT-CCD offers many advantages over traditional Interline CCDs found in many competing digital SLRs.
File Allocation Table (FAT): The primary file system used on camera media storage cards. It is reset to open all available space for new images when the media storage card is formatted.
File Format: A method for arranging the data that makes up an image for storage on a disk or other media. Standard image formats include JPEG and TIFF.
Film Scanner: Scanner dedicated to capturing image files from slides and negatives.
FireWire: A very fast connection (i.e., lots of data transmitted quickly) for linking peripherals to the computer.
Flash Memory: EEPROM: Electrically erasable programmable read-only memory, also called Flash Memory. Digital camera memory cards consist of several flash memory chips and a controller. The controller’s on-board software manages the writing and erasing of data and determines the memory card speed.
Flatbed scanner: Scanner designed to capture images from page-sized or smaller “flat art,” including photographs and artwork.
Flexboard: Microprocessor found in autofocus lenses. Some third-party lenses may require a flexboard up-date to be used on newer cameras.
Focal Length: The distance, usually measured in millimeters, between the lens and the focal plane in the camera. The degree to which light from a scene is magnified by a lens.
Focal Plane: The point onto which a camera focuses an image. In a digital camera the CCD sits on the focal plane.
Focal point: The point where all light rays converge.
Focus-priority: Used on most D-SLRs in their single-shot auto focus mode to lock the shutter until the camera has confirmed focus.
Front Light: Light produced when the sun or light source is behind the camera. This type of lighting is ideal for showing saturated colors, fine details or stopping action.
F-stop: Sometimes synonymous with stop, more specifically a measure of the size of the aperture on a camera.
GIF (Graphics Interchange Format): A standard file format most commonly used for graphics on the World Wide Web. GIF reduces both resolution and color data, making it less effective for photography.
Gigabyte (GB): A measurement of digital data approximately one billion bytes (1000 megabytes).
Gray Market: Products that are not imported by the official U.S. importer, but come into the country through other channels. Gray market items are perfectly legal but may carry different model designations and do not carry a U.S. warranty or are eligible for discounts, rebates or other special offers from the U.S. importer. These items can be priced 10 to 20 percent below U.S. market or street value.
Gray Scale (Or Grayscale): A black & white image composed of a range of gray levels from black to white.
Guide Number (GN): A flash unit Guide Number is equal to 10 times the number value of the f-stop required to yield the correct exposure at a distance of 10 meters at a given ISO setting. (A GN of 45 would require an aperture of f/4.5 at 10 meters while a GN of 28 would require an aperture of f/2.8 at 10 meters.) The larger the GN the more powerful the flash.
Hard Light: Light generated by a clear sky that will produce sharp dense shadows.
Histogram: A feature that reflects the tonal value of a photographed image. It offers the ability to compare where the tones in an image will reside in a digital form, compared to where they are in real life. The histogram offers the best visual to determine if the camera exposure is correct and has the maximum dynamic range. The histogram is one of the most important features at your disposal in digital imaging, not only at the time of capture, but also while editing an image.
ILDC (Interchangeable Lens Digital Camera): (also EVIL)
A new class of camera that uses a larger (DSLR-sized) 4:3 or APS-C sensor in a compact camera body with an electronic viewfinder linked to the camera’s sensor. This eliminates the mirror box and allows for a much smaller camera body with more compact lenses than with a DSLR. Essentially, this is a Digicam like the Sony R1, Olympus C-8080 or Minolta A2 with the ability to use an assortment of lenses. The new Micro Four-Thirds standard is based on this concept.
Image Circle: The size of the circular image cast by the lens on the camera sensor. Full size sensors
(24mm x 36mm) require a larger image circle than a APS-C (15mm x 22mm) sensor.
Image Stabilization (IS): Optical image stabilization utilizes gyroscopic sensors within the lens to detect and compensate for motion or “camera shake.” Alternatively, some cameras achieve IS by moving the image sensor when camera movement is detected.
Inkjet: A low-priced digital printing technology where characters or images are formed by tiny ‘droplets’ being shot at the paper.
Integrated Circuit: A highly engineered package of many circuits working together, usually in a computer chip; one building block of a computer.
Internal Focusing: An internal focusing (IF) lens focuses by shifting selected lens elements with in and independent of the lens outer barrel. The lenses barrel does not change length when the lens is focused. IF lenses are generally smaller and closer focusing than non-IF lenses and require less power since the focus motor does not have to move the lens barrel. IF lenses are well suited where lens-mounted accessories are used.
Interpolation: (Resampling) A way of increasing the apparent resolution of an image by “filling in” the gaps between existing pixels. Artificially increasing or decreasing the number of pixels in an image through the use of an algorithm.
IPTC: International Press Telecommunications Council, Originally designed to allow press photographers to provide information concerning images they sent back to the home office, IPTC fields can be used to store supplemental information about an image. IPTC information differs from EXIF information in that EXIF information is generated by the digital camera and contains information about various camera settings. IPTC fields can be used to “annotate” images with a great deal of information.
Iris: A mechanism that can expand and contract to create circular apertures to control the amount of light passing through a lens.
ISO: (Light Sensitivity) The ISO rating is an indication of light sensitivity in digital photography. Sensitivity is increased by amplifying sensor output, which also increases noise output, much like the increased grain in film with higher light sensitivity.
JABOD: A collection of dissimilar physical computer hard drives that are configured to read as a single virtual volume.
JCII: Japan Camera Inspection Institute formed in 1954 to insure the quality of cameras being shipped out of Japan. Cameras and lenses that passed this inspection received a gold oval sticker. This inspection service was discontinued in the 1990’s as it was felt that it was no longer need as the Japanes quality was some of the highest in the world.
JMDC: Japan Machine Design Center established to eliminate any Japanese camera companies from copying from each other to insure originality. Cameras and lenses that passed this inspection received a gold oval sticker.
JPEG (Joint Photographic Experts Group): A common algorithm for the compression of image files. JPEG compression can vary from nearly lossless to highly lossy. All digital cameras are capable of capturing images in JPEG format, and because JPEG is a standard, JPEG image files can be read by all image-processing software. The JPEG algorithm carefully looks for redundant data in the image (such as large areas of a single color) and removes it, while retaining instructions of how to reconstruct the file when opened in a computer.
JPEG Artifacts: Image defects due to file size compression. These defects appear as tiny rectangles or squarish grain.
Kilobyte (KB): 1000 bytes of memory.
Lateral Transverse: A lens chromatic aberration in which the colors are shifted to one side.
LCD (Liquid Crystal Display): Liquid Crystal Displays are typically a 1.5- to 2.5-inch screen comprised of liquid crystals that are stimulated by electric current to act as a viewfinder and/or preview screen of your frame. The LCD on most, but not all, digital SLRs is only used for viewing already-captured images and navigating menus.
LD, ED, ELD, SD, SLD and UD Glass: (Low-Dispersion, Extra-Low-Dispersion, Extraordinary Low-Dispersion, Super Low-Dispersion, Special Low-Dispersion and Ultra-Low-Dispersion Glass) All these terms refer to a glass type used in lenses. These formulated glasses correct the path of light rays as they pass through the lens, making all colors in the color spectrum focus at the same point. Lenses constructed with these types of glass eliminate or lessen the occurrence of aberrations and some types of artifacts.
NOTE: LD designation is used by Tamron; ED designation is used by Nikon, Olympus, Pentax and Sony; ELD glass was developed by Hoya and is used in some Sigma lenses. It has lower dispersion characteristics than SLD which was used by Sigma. SD glass is a special glass used by Tokina. UD designates a special glass developed by Canon that nearly matches the properties of fluorite, which has abnormally low refraction and dispersion characteristics, which optical glass can’t match. The effect of two UD-glass elemends produces almost the same effect as one fluorite element.
L-Ion (Lithium Ion): A type of rechargeable battery.
Longitudinal axial: A lens chromatic aberration in which all the colors do not focus on the same plane.
Lossless compression: Any form of file compression technique where no loss of image data occurs.
Lossy compression: Any form of file compression technique where some loss of image data occurs.
low self-discharge nickel-metal hydride battery (LSD NiMH): were introduced in November 2005. By using improved separator and improved positive electrode they reduces self-discharge, therefore, lengthens shelf life compared to normal NiMH batteries. They will retain 70 to 85% of their capacity after one year when stored at 20 °C (68 °F), while standard NiMH batteries may lose half their charge in this time period. Low self-discharge cells are marketed as “ready-to-use” or “pre-charged” rechargeables.
Macro: A special type of lens or lens setting primarily used for close-up photography, macro refers to a one-to-one or higher magnification of a subject provided by optics (i.e., a macro lens). The focal length of a macro lens determines how close the lens must be to a subject to attain a one-to-one image capture.
Magnetic media: Data storage media that uses magnetized particles imbedded in the media substrate to write and read data.
Magnification Power: The magnification power of a lens. A 2X macro lens will reproduce an image on the camera sensor that is twice a big as the original subject.
Manual Mode: A shooting mode on a camera that allows the photographer to set both the aperture and shutter speed, giving full control over the camera’s exposure.
Megabyte (MB): One million bytes of memory.
Megapixel: (one million pixels) the number of photodiodes (also known as photosites or pixels) on an image sensor is expressed in megapixels, which in turn is the resolution of the device (a camera, scanner, etc.). Most sensors have one photodiode for each pixel in an image.
Memory Card (Media Card): A memory card is a digital camera storage medium. Although these cards are available in a number of different formats—SD (Secure Digital), CF (CompactFlash), Memory Stick (with several variations), xD-Picture Card—each camera can accommodate only one (sometimes two) of those formats. All cards come in different capacities, measured in megabytes (i.e., 256 MB) or gigabytes (i.e., 2 GB). Some cards are also designed to facilitate high performance, decreasing the time it takes for the camera to write the image data to the card. Card capacities continue to increase in all formats, although not all cameras may be able to use these large-capacity cards. It’s also important to note that, with the exception of MicroDrives (CompactFlash Type II), which have moveable parts like a hard drive, all other media cards are solid-state or flash memory cards and are, therefore, fairly nonvolatile.
Memory Stick®: A type of reusable, removable image storage (Memory Card) developed by Sony.
Metadata: Data about a data. Information stored in digital image files with camera information, such as date and time, shutter speed, aperture, lens setting etc.
Metering: The process of defining the light levels in a scene and providing a measurement for a proper exposure value. Popular modes include center-weighted metering (an average of the frame, with emphasis on the center of the image), spot metering (generally 1 to 3 percent of the image), and evaluative or matrix metering (an average of independent areas of the image). Most digital cameras offer at least two—but generally three—of these metering options.
MicroDrive®: A tiny hard drive that fits in a type II compactFlash® slot on a camera.
Micromotor: Non ring-type motor used in some lens for auto-focus. These are al gear driven drives that are somewhat slower and nosier that ring-type AF lens
NiMH (Nickel Metal Hydride): A type of rechargeable battery.
Monochromic: Having or appearing to have only one color. Term used to describe black and white.
MOS Sensor: (Metal Oxide Semiconductor) sensors developed by AppliedSensor and being used by Olympus and Panasonic. The live MOS sensor is a new generation sensor that offers the high image quality of a CCD sensor with the low power consumption of a CMOS sensor, making it possible to display Live View images on the cameras LCD for extended periods of time.
Called the Live MOS Sensor, it offers high processing speed, high sensitivity, low noise, and low power consumption, as well as image quality that approach that of FFT-CCD sensors. It is a new-generation NMOS sensor that was spawned by a high level of synergy between NMOS technology and the signal enhancement and other digital technologies in which Olympus has many years of experience.
MTBF: Mean Time Between Failures, how long you would have to run a device before expecting it to fail.
MTF Data: Modular Transfer Function, A very accurate tests that yells a graph that indicates a lens contrast and sharpness both radially and tangentiall, with full aperture open an at f/8. The higher the reading on the graph the better the lens. A professional lens should have a reading over 95% at 5 lines/mm in both directions and over 50% at 20 lines/mm.
Multithreading: The ability for a software application (edition program) to perform multiple tasks at the same time.
N MOS Sensor: (negative-channel metal oxide semiconductor) A CMOS sensor sibling, NMOS is becoming part of the digital camera lexicon as well. It is a sort of hybrid CCD/CMOS sensor, in that they generate an electrical signal that is passed off to a processor, but they are said to excel at getting excellent quality from each pixel site.
Nodal Point: The point in the lens where the light paths cross or the image flips from upright to upside down before being focused on the camera sensor.
Noise: Image artifacts caused by complex variations with color that manifest themselves as grain on an image. Excessive noise, which is most often seen first in shadows, usually results in an objectionable-looking image. High-resolution digital cameras with small image sensors, where more pixels are forced to live in a smaller space and have physically smaller photodiodes are more subject to noise than sensors with larger photodiodes. High ISO (light sensitivity) also generates image noise. Most digital cameras are equipped with some form of noise reduction that is either automatically triggered with high ISOs or long exposures or, in higher-end cameras, can be turned on and off manually. When noise reduction is applied in camera (or via image-editing software), it can result in softened or blurred details to lessen the visibility of the noise.
Normal Lens: A lens that has a field of view that is equivalent to the field of view of the human eye, roughly 50mm.
OLED: (Organic Light-Emitting Diode) Offers a screen that looks like an LCD (Liquid Quarts Display) only updates quicker, uses less power and is brighter, sharper, more vibrant and readable from the sides, even at an angle of 165 degrees off center.
Optical media: Data storage media that uses a laser to write and read data; can be quite long lasting.
Optical Nodal Point: (Panorama pivot point): It is the distances forward
from the film plane position in the camera body the length of the lens in mm.
For a 100mm lens it is a point 100mm forward of the focal plane. On a zoom
lens it is the length in mm that the lens is zoomed to.
Optical resolution: The maximum physical resolution of a device. Optical resolution provides better quality than interpolated resolution, which uses software to create additional image information.
Overexposed: An image that was exposed for too long. As an image becomes more overexposed it gets brighter and brighter. Highlights and light color areas wash out to completely white. Once highlights are lost, burned out, they can not be recovered.
Parfocal zoom lens: A zoom lens design that holds its focus when you zoom.
Passive Auto Focus System: Does not use an infrared ranging beam to determine distance. Passive autofocus cameras use the light falling on photocells to determine the correct focus. There are two different types of Passive Auto Focus Systems used: Phase-detection and Contrast-based.
Passive Contrasted-based Auto Focus System: Used on most consumer cameras. This system is slower that the phase-detected system and must have some contrast in order to focus. Does not work well with action subjects.
Passive Phase-detection Auto Focus System: Used on all D-SLRs, some
light coming through the lens is diverted to an AF module, were it is split into
two parts and directed onto two sensors. These sensors determine where the distance.
Predictive continuous auto focus: Also referred to as AI focus mode. Takes successive focus readings and determines the direction and speed of the subject so it can anticipate the next focus point. Works best with subjects moving in a constant direction and speed.
Pentium: A microprocessor manufactured by Intel available in Windows-based computers.
Peripheral: A piece of hardware that’s not part the CPU and allows some important function of the computer, such as scanning or printing. Usually an external device.
Photo CD: A storage system for photographs developed by Kodak to use a CD as media; images can be added to CD at any time.
Picture CD: Another CD storage system developed by Kodak and others, to allow images to be put on disk at the time of processing.
Pixel: Short for picture element (pix/picture, el/element). The smallest element of a picture that can be controlled by the computer.
Plano-Parallel: A term used with lens filters to indicate that every point on each side of the filter is perfectly flat and parallel with the opposite side.
Plug and Play: A standard that allows a computer operating system to recognize a device and install it fairly easily.
PPI (Pixels per Inch): The number (density) of pixels per inch in an image, often incorrectly used interchangeably with dpi. Increasing the density of pixels (PPI), and the optimum print size decreases, decreasing the density (PPI) and the optimum print size increases.
Primary Colors: The red, green and blue hues used to create all other colors.
Profile: Printer profiles are created in a standard way by measuring the color values after printing a chart on each of the paper-type-and-ink combinations. These files will have a .ICC or .ICM extension.
RAM (Random Access Memory): The computers memory that’s actually active for use in programs; comes on special chips.
Raw: An image-capture option containing the maximum information available from a sensor without the application of in-camera processing algorithms. This allows photographers to have more control over the final image by processing the image manually in a software program. The format is offered by many high-end compact digital cameras as well as D-SLRs. Each camera company has its own RAW format and corresponding software to support the format. Image-editing applications like Adobe Photoshop are also capable of opening and processing images shot in RAW.
Real time: The actions of the computer are seen at the same time as you perform them.
Reciprocity: Exposure parameters have a reciprocal relationship so that different combinations of parameters produce the same exposure. For example, setting you camera to a shutter speed of 1/250th of a second at f8 is the same as setting it to 1/125th at f16.
Release-priority: Used on most D-SLRs, continuous auto focus mode, to allows the shutter to trip at any time, weather the subject is in focus or not
Removable media: Any storage system package that can be removed from the data drive, such as a Zip disk or CD-R.
Resolution: Camera resolution expressed in the number of photodiodes (megapixels) on the image sensor. More megapixels equals higher resolution. It’s important to note that many factors go into image quality, and resolution is only one of them. If you have a poor-quality lens on a high-resolution camera, you’ll get a high-resolution image of poor quality. Higher-resolution image files can produce larger prints than lower-resolution files.
RGB: The three primary colors of red, green and blue that our eyes perceive as the basis for every other color. When added together equally, they make pure white. Most, but not all, digital photography uses an RGB color space.
Ring-type motor: Auto focus motor found in some lens that are very quite and fast. They also have the ability to allow manual over-ride focusing when in auto focus mode.
Ringing: White, ring-like border around distinct edges in a photo that occurs when the photo has been over sharpened.
ROM (Read only memory): A special type of permanent computer memory that can’t be altered. It keeps its information even when the computer is shutdown.
RSS (Really Simple Syndication): A family of web feed formats used to mpublish blogs or news feeds.
Scanner (drum, flatbed, or slide): A sensing device that captures photos, slides, or negatives and translates them into digital files for the computer.
SCSI (Small Computer Systems Interface): A very fast system that connects peripherals to the CPU, called a “scuzzie.”
SDIO: Secure Digital Input/Output. SDIO devices work in a Secure Digital memory card slot. There are many such devices, including tiny hard drives, GPS gadgets, or, in this case, Wi-Fi networking.
Selective focus: A selective part of the image is in focus and the balance of the image is less in focus. Special lens, such as the Lensbaby, are designed to produce this effect. This effect works best when there’s a single subject.
Sensor: The light-sensing part of a digital camera, usually a CCD or CMOS chip.
Service bureau: A business providing image services such as Photo CDs, slides or large prints.
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 to light. Many digital cameras do not have physical shutters, but mimic shutter functionality by simply activating and deactivating the image sensor to record an image.
Shutter Priority: A shooting mode on a camera. Shutter priority lets the photographer 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 expose the focal plane. This controls, in conjunction with the aperture setting, the amount of light that hits the sensor, thereby determining the exposure. At the same time, the shutter speed can affect whether or not the image is in focus, especially if the subject is moving. Faster shutter speeds are measured in fractions of one second—averaging 1/4000th of a second or higher. Many cameras also allow the shutter speed to be set in full seconds for longer exposures.
Sidecar: Instruction written, as Metadata, for a RAW file image.
Side Light: Light produced when the sun or light source is at right angles to the camera. This type of lighting produces shadows and is ideal for showing textures and forms.
Single Lens Reflex (SLR/D-SLR): A camera whose viewfinder looks through the same lens that the camera uses to make exposure.
SmartMedia®: A type of reusable, removable storage.
Soft Light: Light produced by overcast skies that will produce low contrast images with little or no shadows
Spot Meter: A light meter that measures a very narrow circle of the scene.
Stop: (1) The double or halving of any value. (2) A measure of the light that is passing through a camera lens to the focal plane. Every doubling or halving of light – either through changes in aperture, shutter speed, or ISO – is one stop.
Telephoto: a lens with a focal length that is longer then normal. As a lens gets more telephoto, its field of view decreases.
Thumbnail: A small, low-resolution version of an Image.
TIFF (Tagged Image File Format): An important and lossless bitmap image format common to most image processing programs. A standard image file format for bitmapped graphics. TIFF files are uncompressed and, therefore, very large compared to compressed formats. Not only do TIFF files occupy more hard-drive space for storage, but also it takes longer for the camera to write these files to a media card, thereby slowing down some aspects of camera performance. Because TIFF is a standard, TIFF image files can be read by all image-processing software.
Trademark: A word, name, symbol or device or any combination thereof, used to distinguish a particular good from another in the market place.
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’.
TTL Flash: (through the lens) flash metering: required the photographer to perform distance calculations by hand.
TWAIN: A standard protocol that allows communication from various types of scanners to the software.
UD, LD and ED Glass: (Low-Dispersion, Extra-Low-Dispersion and Ultra-Low-Dispersion Glass) All these terms refer to a glass type used in lenses. These formulated glasses correct the path of light rays as they pass through the lens, making all colors in the color spectrum focus at the same point. Lenses constructed with these types of glass eliminate or lessen the occurrence of aberrations and some types of artifacts.
UDMA (Ultra Direct Memory Access): Lexar announced in June 2007 a new
Compact Flash card with a speed rating of 300X, write speed of 45MB per sec. NOTE: Camera must be UDMA certified to use these cards
Underexposed: An image that was not exposed enough. In an underexposed image, dark, shadow areas turn to completely black.
Unsharp Masking (USM): A sharpening technique that looks at contrasting edges within an image and intensifies them.
USB (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.
Variable Aperture Zoom Lenses: A lens in which the aperture decreases in size as the lens is zoomed from wide-angle to a longer focal length. These lens are much less expensive than fixed zoom lenses. Since to day’s cameras all use TTL metering there is little disadvantage except that a smaller aperture at the longest focal length produces a longer depth of field (DOF) making it harder to produce a background that is out of focus.
Varifocal zoom lens: A zoom lens design that does not hold its focus as you zoom, requiring you to refocus after each zoom.
VGA resolution: 640X480 pixels.
Video board: A part of file CPU that processes display information for the monitor.
Virus: A malicious implant some warped individuals put info software that can cause failures of systems including data or memory logs.
White balance: A calibration of color temperature to a degree on the Kelvin scale where white reads as white, rather than the varying shades of white caused by different lighting conditions. White in the morning, for instance, is a cooler blue of white, especially when compared to the very warm yellow of afternoon sun. White-balance settings can be changed within the digital camera to adjust for sun, shade, tungsten and fluorescent lighting; automatic white balance is also an option, although accuracy is generally inconsistent. Custom or manual white balance is available in many cameras and is accomplished by pointing the camera at a white surface and clicking the shutter. Higher-end cameras have a variety of white-balance options, including the ability to set Kelvin temperatures manually.
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.
World Wide Web: That part of the Internet where text, pictures, and graphics come together in an integrated unit or page.
.XML: (Extensible Markup Language) an Adobe file using a tagging language
designed to be very flexible and to share data across different computer
programs. XML files are text based and can be viewed in many different Web
browsers and text editors.
.XMP: Metadata file (EXtensible Metadata Platform) initiated by Adobe to promote a standard for photography metadata. RAW sidecar information files are text files with an .XMP extension.
Zip drive: A drive developed by Iomega for storing information that uses 100 or 250 MB storage in removable media.
Zone system: A method of calculating exposure.
Zoom: Lens with a variable focal length, often wide-angle to telephoto, that allows photographers to change how much of a scene can be captured by the camera.
Zoom Ratio: Referred to as “X” in camera and zoom lens ratings. Ratio is determined by dividing the shortest lens focal length into the lens longest focal length, (a 28mm-280mm lens has a zoom range of 10X).
1:1 Viewing Ratio: Viewing an image at a 1:1 ratio, meaning that one pixel on your monitor equates to one pixel in the image. At any other zoom setting the display on the monitor is not at a 1:1 ratio, so that either one pixel on the monitor represents multiple pixels in the image, or one pixel in the image requires multiple pixels on the monitor. When you view the image at a 100% zoom setting, you are seeing the actual effect on the actual pixels in the image.
© Sonny Saunders
September 27, 2006
Revised: July 1, 2009