Glossary of Terms Options

[Dracofish]

Aperture - The size of the opening in the diaphragm of a lens through which light passes. Also known as an f-stop. A larger aperture (smaller f-stop numbers) results in more light being let through. A smaller aperture (higher f-stop numbers) results in less light being let through. Aperture is directly related to DOF.

Aperture Priority mode - The automatic exposure mode in which the user sets the aperture and the camera automatically sets the appropriate shutter speed to produce a correct exposure. It is often used in landscape photography to produce greater depth of field by choosing smaller apertures (higher f-stop numbers).

Autofocus (AF) - Automatic, motorized focusing.

Average Metering - Through-the-lens (TTL) exposure metering that takes into consideration the illumination over the entire image.

Bracketing - The technique of taking additional exposures that are over and under a "normal" exposure setting to ensure that a desired exposure is achieved from the several frames exposed. It is often used in tricky lighting conditions. This is especially useful to "merge" the light and dark aspects of two different photographs of the same shot to get one perfectly exposed piece.

Bulb Mode - An exposure mode that keeps the shutter open (or activated in digital cameras) for as long as the shutter release button is held down. Often used in nighttime photograhy for long exposures.

Cable release - A cable device that allows for the remote release of the shutter. Helps prevent camera shake.

Card reader - A device for transferring pictures from a memory card into a computer.

CCD (charded coupled device) image sensor - The kind of light-gathering device used in scanners, digital cameras, and camcorders that converts the light passing through a lens into an electronic equivalent of the original image.

CIELAB - A color system created by the Commission Internationale de l'Eclairage to produce a color space consisting of all visible colors. The CIELAB system, sometimes shortened to just "Lab," forms the basis for most contemporary color-matching systems and lets you convert, for example, RGB image to Lab to CMYK to produce accurate color-matching.

CMOS (complimentary metal oxide semiconductor) - An alternative to the CCD (charged coupled device) imageing chips used by some digital cameras. The CMOS chip is simpler to make, so it costs less. It also uses less power than CCD chips, so it doesn't drain batters as fast. The downside is that the chip does not perform as well as CCD imagers under low-light conditions, but recent digital SLR models from Kodak and Canon are said to have improved performance under less than ideal lighting conditions.

CMYK (cyan, magenta, yellow, and black) - For printed reproduction an image is separated into varying percentages of these four colors, which is why CMYK output is called "separations." Computer printers also use CMYK dyes and inks to produce photographic-quality prints. Compare with RGB.

Coil sync cord - An extension cord for an accessory (shoe-mount) flash unit that permits off-camera flash. It allows for more creative photography, because you can control the specific direction of the light instead of producing the flat "flash on camera" look.

Compression - A method of removing unneeded data to make a file smaller without losing any critical information, or in the case of a photographic file, image quality.

Continuous autofocus - An automatic focusing system that constantly tracks a moving subject. Useful in sports and action photography for keeping the principal subject in focus.

Contrast range - the difference in intensity between light and dark areas in a scene. High contrast scenes are difficult to expose correctly.

Daylight fill-in flash - The process of balancing the light from a flash with the available daylight.

Density range - The difference between the minimum and maximum tonal values that film or a digital camera's image sensor can register.

Depth of Field (DOF) - The distance of acceptable sharpness that is in front of and behind a specific focus point. A larger aperture (lower f-stop number) results in a shallower DOF, rendering only a small amount of the scene in focus. This is useful in more artistic shots where a specific subject is to be emphasized against a distracting background. A smaller aperture (higher f-stop number) results in a wider DOF, resulting in much more of the scene being in focus.

Diffuser - A device that diffuses, or softens, harsh sunlight for a more pleasing effect. Useful in outdoor portraiture.

Digital Noise - Appears as "grain" in digital image files. As a camera's ISO setting increases, digital noise also increases. Noise is also caused by slow shutter speeds in low-light conditions.

Digital zoom - Not a true optical zoom lens, but rather a technique for enlarging part of the image sensor's frame. Not as sharp as optical zoom.

Duotone - The process of adding one or more colors to a black-and-white image.

Dye-sublimation printer - A printer that applies dye from a dry ribbon onto specially treated paper. Heat from a print head vaporizes the dye, which is transferred onto the paper to produce a true photo-quality print.

EV (exposure value) - A numeric value used to describe the exposure. A variety of shutter speed and aperture combinations can produce the same exposure with a constant film speed: for example, 1/250 (of a second) + f/2 = 1/125 + f/2.8 = 1/60 + f/4 = 1/30 + f/5.6 = 1/15 + f/8, etc. Note: this is different from exposure index.

Exposure compensation - A feature found on both film and digital cameras that lets the user compensate (plus or minus) in an exposure setting in relatively small increments, such as one-half or even one-third of an f-stop to produce the desired exposure.

Filter - A piece of glass or optical plastic that fits over a camera lens for a creative, protective, or corrective effect. Digital filters (Photoshop-compatible plug-ins) are also available for image enhancement and correction after a photograph has been captured.

Fixed focal-length lens - A lens with only one focal length, unlike a zoom lens which offers selectable focal lengths.

Flash extender - A device that attaches to an accessory flash that extends the flash's range. Useful in sports and wildlife photography.

Focal length - Measured in millimeters, the length of a lens.

Fractal - A graphics term, originally defined by mathematician Benoit Mandelbrot, to describe a category of geometric shapes charachterized by irregular shape and design and used by computer software, such as Genuine Fractals, as a mathematical model for resizing and enlarging image files.

F-stop - A measure of the size of the opening in a lens calibratedto a corresponding focal lenth. Thse numbers are typically stated as f/1.4, 2, 2.8, 5.6, 11, 16, 32, etc. Large f-stops (e.g., f/2.8) allow a lot of light to enter the camera. Smaller f-stops (e.g., f/22) allow less light to enter the camera.

GIF (graphics interchange format) - A compressed image file formal that was originally developed by CompuServe Information Systems and is platform-independent, meaning that a GIF file created on a Macintosh is also readable by a Windows graphics program. Pronounced like the peanut butter.

Grain - course dots that you can see in a picture. As the film's ISO increases, grain also increases.

Grayscale - A series of gray tones ranging from white to pure black. The more shades or levels of gray, the more accurately an image will look like a full-toned black-and-white photograph. Most scanners will scan from 16 to 256 gray tones. A grayscale image file is typically one-third the size of a color tone.

Hot Shoe - Slot on the top of many cameras into which a portable flash unit is attatched.

Inkjet Printer - A type of printer that sprays tiny streams of quick-drying ink onto paper to produce high-quality output. Circuits controlled by electrical impulses or heat determine exactly how much ink--and what color--to spray, creating a series of dots or lines that form a printed image.

IS (image stabilization) - Technology on Canon EOS lenses, called VR (vibration reduction) on Nikon lenses, that reduces camera shake.

ISO - Speed rating for film and equivalents (in digital cameras) that measures light sensitivity. The higher the ISO number, the greater the light sensitivity.

JPEG (Joint Photographic Experts Group) - Mothod of compressing and storing photographic image files. JPEG was designed to discard information the eye cannot normally see and uses compression technology that breaks an image into discrete blocks of pixels, which are then divided in half until a compression ratio from 10:1 to 100:1 is achieved. The greater the compression ratio that's produced, the greater the loss of image quality and sharpness. Unlike other compression schemes, JPEG is a "lossy" method. By comparison, the LZW compression method used in file formats such as TIFF is lossless--meaning that no data is discarded during compression.

Landscape (mode) - An image orientation that places a photograph across the wider (horizontal) side of the monitor or printer.

Layer - In image-enhancement programs (like Adobe Photoshop), one of the several on-screen independent levels for creating separate--but cumulative--effects for an individual photograph. Layers can be manipulated independently and the sum of all the individual effects on each layer make up what you see as the final image.

LED (ligh emitting diodes) - Provide information in a camera's viewfinder, such as flash-ready and focus confirmation.

Lens flare - Hot spot in a picture that is caused by direct light hitting the front element of the lens and reflecting through all the other glass elements in a lens.

LZW (Lempel-Ziv-Welch) - A compression algorithm, currently owned by Unisys and used by Adobe Photoshop to perform lossless compression on TIFF files.

Macro lens - A lens specifically designed for close-up photography.

Manual mode - An exposure mode that requires the user to set both the shutter speed and f-stop.

Megapixel - Refers to the number of millions of pixels in a digital camera's image sensor. A 4 megapixel camera has an image sensor with 4 million pixels.

Panning - The process of following a subject from left to right (or vice versa) in the viewfinder as it moves past the photographer. Using a slow shutter speed, the photographer takes an exposure (or several exposures) when the subject is directly in front of him or her. The result is a picture in which the background is blurred (streaked) and the subject is sharp, creating the feeling of motion and speed.

Pixel (picture element) - One of the thousands of colored dots of light that, when combined, priduce an image on a computer screen. A digital photograph's resolution, or image quality, is measured by the width and height of the image as measured in pixels.

Plug-in - A small software application that is an "add-on" and that expands the capabilities of Photoshop or any compatible image-enhancement program.

Polarizing filter - A filter that can reduce glare on water, glass, and foliage. It can also darken a blue sky and whiten white clouds. Is not effective with metallic surfaces.

Program mode - An exposure mode on a camera that automatically sets both the aperture and shutter sped for a correct exposure. Also called full auto mode.

Red-eye - In dark conditions, an effect is caused by light from a camera's flash reflecting off the blood vessels in the black of the eye. It can be reduced by making the room brighter, by using an off-camera flash, or by utilizing the red-eye reduction mode that some cameras and flashes offer.

Resolution - The number of dots per inch (dpi) or pixels per inch (ppi) that a computer device, such as a monitor or printer, can produce. A digital photograph's resolution, or image quality, is measured by the image's width and height as measured in pixels. The higher the resolution of an image--the more pixels it has--the better it's image quality. An image with a resolution of 2,048 x 3,072 ppi has better resolution and more photographic quality than the same image digitized at 128 x 192 ppi.

RGB (red, green, blue) - Color monitors use red, blue, and green signals to produce all of the colors tha tyou see on the screen. The concept is built around how these three colors of light blend together to produce all visible colors. Compare with CMYK.

Ringlight - A ring-shaped device that fits over a lens for even or ratio lighting in macro and close-up photography.

Shutter lag - The time delay between the pressing of the shutter release and the actual taking of the picture.

Shutter Priority mode - An exposure mode that lets the user choose the shutter speed while the camera automatically selects the appropriate aperture for a correct exposure.

Shutter speed - The actual length of time the shutter is open (or the digital image sensor is activated).

SLR (single-lens reflex) - In an SLR camera, the image created by the lens is transmitted to the viewfinder via a mirror and the viewfinder image corresponds to the actual imaging area.

Spot metering - An in-camera metering mode that takes a reading of a small area in a scene. Useful when the subject is in a high-contrast setting.

Telephoto lens - A lens that, in effect, brings the subject closer. Useful in wildlife, portraiture, and sports photography.

TIFF (tagged image file format) - A bit-mapped file format that can be any resolution and includes black-and-white or color images. TIFF files are supposed to be platform-independent, so files created on your Macintosh can (almost) always be read by any Windows graphics program.

TTL (through-the-lens) - A metering system in which the camera measures the actual light entering the lens.

White balance control - A feature on a digital camera that lets the user set the camera for the existing lighting conditions, such as sunny, shady, flash, fluorescent, and incandescent.

Wide-angle lens - A slens that takes in a wide view. Useful for landscape photography.

Zoom-lens reflex (ZLR) camera - A digital camera with a built-in (noninterchangeable) zoom lens.

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Compiled from the glossary by Joe Farace in the book "Rick Sammon's Complete Guide to Digital Photography: 107 Lessons on Taking, Making, Editing, Storing, Printing, and Sharing Better Digital Images" by Rick Sammon.