ambient light The natural or artificial light within a scene. Also called available light.
aperture The lens opening through which light passes. Aperture size is adjusted by opening or closing the diaphragm. Aperture is expressed in f/numbers, such as f/8 and f/5.6.
artifact An unintentional or unwanted element in an image caused by an imaging device or appearing as a byproduct of software processing, such as compression, flaws from compression, color flecks, and digital noise.
artificial light The light from an electric light or flash unit. The opposite of natural light.
Auto ISO Considering the lighting, lens used, and exposure settings, the camera automatically selects an appropriate ISO for handheld shooting, from ISO 100-6400.
autofocus The camera automatically focuses on a subject by using the selected autofocus point shown in the viewfinder or tracks a subject in motion and then creates a picture with the subject in sharp focus. Press the Shutter button halfway down to activate this.
automatic exposure The camera meters the light in the scene and automatically sets the shutter speed (ISO) and aperture necessary to make a properly exposed picture.
automatic flash When the camera determines that the existing light is too low to get either a good exposure or a sharp image, it automatically fires the built-in flash unit.
axial chromatic aberration A lens phenomena that bends different color light rays at different angles, thereby focusing them on different planes. Axial chromatic aberration shows up as color blur or flare.
backlighting Light that's behind and pointing to the back of the subject.
barrel distortion A lens aberration where straight lines bow outward from the center.
bit depth The number of bits (the smallest unit of information used by computers) used to represent each pixel in an image that determines the image's color and tonal range.
blinkies When reviewing images on the LCD, the blown-out highlights blink.
blocked up Describes areas of an image lacking detail because of excess contrast.
blooming Bright edges or halos in digital images around light sources and bright reflections caused by an oversaturation of image-sensor photosites.
bokeh Shape and illumination characteristics of the out-of-focus area in an image.
bounce light Light that's directed toward an object, such as a wall or a ceiling, so that it reflects light back onto the subject.
bracketing To make multiple exposures — some above and some below — the average exposure calculated by the light meter for the scene. Some digital cameras can also bracket white balance to produce variations from the white balance calculated by the camera.
brightness The perception of the light reflected or emitted by a source. The lightness of an object or image. See also luminance.
buffer Temporary storage for data in a camera or computer.
calibration In hardware, a method of changing the behavior of a device to match established standards, such as changing the contrast and brightness on a monitor. In software, calibration corrects the color cast in shadows and allows adjustment of non-neutral colors that differ between an individual camera and the camera's profile used by Camera Raw.
camera profile A process of describing and saving the colors that a specific digital camera produces so that colors can be corrected by assigning the camera profile to an image. Camera profiles are especially useful for photographers who often shoot under the same lighting conditions, such as in a studio.
catchlight Highlights in a subject's eyes.
chimping Reviewing images on the LCD right after you've taken them.
chromatic aberration A lens phenomena that bends different color light rays at different angles, thereby focusing them on different planes. Two types of chromatic aberration exist. See axial chromatic aberration and chromatic difference of magnification.
chromatic difference of magnification
Chromatic aberration that appears as color fringing where high-contrast edges show a line of color along borders. The effect of chromatic aberration increases at longer focal lengths.
color balance The color reproduction fidelity of a digital camera's image sensor and of the lens. In a digital camera, color balance is achieved by setting the white balance to match the scene's primary light source.
color cast The presence of one color in other colors of an image. A color cast appears as an incorrect overall color shift often caused by an incorrect white balance setting.
color space In the color spectrum, a subset of colors included in the chosen space. Different spaces include more or fewer colors.
color/light temperature A numerical description of the color of light measured in degrees Kelvin. Warm, late-day light has a lower color temperature. Cool, early-day light has a higher temperature. Midday light is often considered to be white light (5000 K). Flash units are often calibrated to 5000 K.
compression A means of reducing file size. See lossy and lossless.
contrast The difference in range of tones from light to dark in an image or scene.
contrasty A term used to describe a scene or image with great differences in brightness between light and dark areas.
cool The bluish color associated with higher color temperatures. Also describes editing techniques that result in an overall bluish tint.
daylight balance Describes the color of light at approximately 5500 K — such as midday sunlight or an electronic flash.
dedicated flash A method in which the camera measures the ambient light and determines the flash output accordingly. Also known as TTL, or Through-the-Lens.
diffuser Material, such as fabric or tissue, placed over the light source to soften the light.
dynamic range The difference between the lightest and darkest values in an image. A camera that can hold detail in both highlight and shadow areas over a broad range of values is said to have a high dynamic range.
exposure The amount of light reaching a light-sensitive medium — film or a sensor. The result of the intensity of light multiplied by the length of time the light strikes the medium.
exposure compensation A camera control that allows the photographer to overexpose (the plus [+] setting) or underexpose (the minus [-] setting) images by a specified amount from the metered exposure.
exposure meter A built-in light meter that measures the amount of light on the subject. EOS cameras use reflective meters.
extender An attachment that fits between the camera body and the lens to increase the focal distance of the lens.
extension tube A hollow ring attached between the camera lens mount and the lens that increases the distance between the optical center of the lens and the sensor and decreases the minimum focusing distance.
fast Refers to film, digital camera settings, and photographic paper that have high sensitivity to light. Also refers to lenses that offer a very wide aperture, such as f/1.4, and to a short shutter speed.
fill flash A lighting technique where the Speedlite provides enough light to illuminate the subject in order to eliminate shadows. Using flash for outdoor portraits brightens the subject in conditions where the camera meters light from the broader scene.
filter A piece of glass or plastic usually attached to the front of the lens to alter the color, intensity, or quality of the light. Filters are also used to alter the rendition of tones, reduce haze and glare, and create special effects, such as soft focus and star effects.
flare Unwanted light reflecting and scattering inside the lens, causing a loss of contrast and sharpness and/or artifacts in the image.
flat Describes a scene, light, photograph, or negative that displays little difference between dark and light tones. The opposite of contrasty.
fluorite A lens material with an extremely low index of refraction and dispersion when compared to optical glass.
focal length The distance from the optical center of the lens to the focal plane when the lens is focused on Infinity. The longer the focal length is, the greater the magnification.
focal point The point on a focused image where rays of light intersect after reflecting from a single point on a subject.
focus The point at which light rays from the lens converge to form a sharp image. Also, the sharpest point achieved by adjusting the distance between the lens and image.
Front Curtain Sync Default setting that causes the flash to fire at the beginning of the exposure when the shutter is completely open. See also Rear Curtain Sync.
f-stop/f-number A number representing the maximum light-gathering ability of a lens or the aperture setting at which a photo is taken. It's calculated by dividing the focal length of the lens by its diameter. Wide apertures are designated by small numbers, such as f/2.8. Narrow apertures are designated by large numbers, such as f/22. See also aperture.
ghosting A type of flare that causes a clearly defined reflection to appear in the image symmetrically opposite to the light source, creating a ghost-like appearance. Ghosting is caused when the sun or a strong light source is included in the scene and a complex series of reflections among the lens surfaces occurs. This can also occur when using flash with an extremely slow shutter speed.
gray-balanced The property of a color profile where equal values of red, green, and blue correspond to a neutral gray value.
gray card A card that reflects a known percentage of the light that falls on it. Typical grayscale cards reflect 18% of the light. Gray cards are standard for taking accurate exposure-meter readings and for providing a consistent target for color-balancing during color-correction in an image-editing program.
grayscale A scale that shows the progression of tones from black to white by using tones of gray. Refers to rendering in black, white, and tones of gray. Also known as monochrome.
highlight A term describing a light or bright area in a scene or the lightest area in a scene.
histogram A graph that shows the distribution of tones in an image.
hot shoe A camera mount that accommodates a separate external flash unit or microphone. Inside the mount are contacts that transmit information between the camera and the flash unit and that trigger the flash when the Shutter button is pressed.
hue The dominant wavelength of a color. A color system measures color by hue, saturation, and luminance.
Image Stabilization A technology that counteracts hand motion when handholding at slow shutter speeds or using long lenses.
Infinity The farthest position on the distance scale of a lens (~ 50 feet and beyond).
ISO (International Organization for Standardization) A rating that describes the sensitivity to light of film or an image sensor. ISO in digital cameras refers to the amplification of the signal at the photosites. Also commonly referred to as film speed.
Kelvin A scale for measuring temperature based on absolute zero. The scale is used to quantify the color temperature of light.
linear A relationship where doubling the intensity of light produces double the response. The human eye doesn't respond to light in a linear fashion. See also nonlinear.
lossless A term that refers to file compression that discards no image data. TIFF is a lossless file format.
lossy A term that refers to compression algorithms that discard image data, often in the process of compressing image data to a smaller size. The higher the compression rate, the more data that's discarded and the lower the image quality. JPEG is a lossy file format.
luminance The light reflected or produced by an area of the subject in a specific direction and measurable by a reflected light meter.
metadata Data about data or, more specifically, information about a file. Data that the camera embeds in image files includes aperture, shutter speed, ISO, focal length, date of capture, and other technical information. You can add additional metadata in image-editing programs, including name and copyright.
middle gray A shade of gray that has 18% reflectance.
midtone An area of medium brightness; a medium gray tone in a print. A midtone is neither a dark shadow nor a bright highlight.
mirror lockup Camera function that allows the mirror, which reflects the image to the viewfinder, to flip up without the shutter being released. This reduces vibration from mirror movement or allows manual sensor cleaning.
moiré Bands of diagonal distortions caused by interference between two geometrically regular patterns in a scene or between the pattern in a scene and the image sensor grid.
MPEG-4 A collection of methods defining compression of audio/visual (AV) digital data.
neutral density filter A filter attached to a lens or light source to reduce the required exposure.
noise Extraneous visible artifacts that degrade digital image quality. In digital images, noise appears as multicolored flecks, also referred to as grain. Grain is most visible in high-speed images captured at a high ISO.
nonlinear A relationship where a change in stimulus doesn't always produce a corresponding change in response. If the light in a room is doubled, the room isn't perceived as being twice as bright. See also linear.
normal lens or zoom setting A lens or zoom setting whose focal length is approximately the same as the diagonal measurement of the film or image sensor used. In 35mm format, a 50-60mm lens is considered to be a normal lens. A normal lens more closely represents the perspective of normal human vision.
open up To switch to a lower f-stop, which increases the size of the diaphragm opening.
optical zoom Magnification that results from adjusting the optical elements in the lens.
overexposure Exposing film or a sensor to more light than is required for an acceptable exposure. The resulting picture is too light.
panning A technique of moving the camera horizontally to follow a moving subject, which keeps the subject sharp but creates a creative blur of background details.
Peripheral Illumination Correction This compensates for light falloff by using optical characteristics stored in the camera.
photosite The place on the image sensor that captures and stores the brightness value for one pixel in the image.
pincushion distortion A lens aberration causing straight lines to bow toward the center.
plane of critical focus The most sharply focused part of a scene.
polarizing filter A filter that reduces glare from reflective surfaces, such as glass or water, at certain angles.
PPI (pixels per inch) The number of pixels per linear inch on a monitor or image file. Used to describe overall display quality or resolution.
Rear Curtain Sync Camera setting that allows the flash to fire at the end of the exposure, right before the second, or rear, curtain of the shutter closes. With slow shutter speeds in ambient light, this feature creates a blur behind a moving subject, visually implying that movement. With flash, this setting freezes the subject at the end of the exposure, resulting in a more realistic action shot. See also Front Curtain Sync.
reflected light meter A device — usually a built-in camera meter — that measures light emitted by a photographic subject.
reflector A surface, such as white cardboard, used to redirect light into shadow areas.
resolution The number of pixels in a linear inch. Resolution is the amount of information present in an image to represent detail in a digital image. Also the resolution of a lens that indicates the capacity of reproduction of a subject point of the lens. Lens resolution is expressed as a numerical value, such as 50 or 100 lines, which indicates the number of lines per millimeter of the smallest black and white line pattern that can be clearly recorded.
ring flash A flash unit with a circular light that fits around the lens or to the side and produces virtually shadowless lighting.
saturation As it pertains to color, a strong pure hue undiluted by the presence of white, black, or other colors. The higher the color purity is, the more vibrant the color.
self-cleaning sensor Technology attached to the sensor's front layer (low-pass filter) that shakes off dust automatically when the camera is turned on or off or activated manually.
sharp The point in an image at which fine detail and textures are clear and well-defined.
sharpen A method in image-editing of enhancing the definition of edges to make an image seem sharper. See also unsharp mask.
slave A means of synchronizing one flash unit to another so that one controls the other.
slow Refers to film, camera settings, and photographic paper that have low sensitivity to light, requiring relatively more light to achieve accurate exposure. Also refers to lenses that have a relatively wide aperture, such as f/3.5 or f/5.6, and to a long shutter speed.
speed Refers to the relative sensitivity to light of photographic materials, such as film, sensors, and photo paper. Also refers to the ISO and the ability of a lens to let in more light by opening the lens to a wider aperture.
spot meter A device measuring reflected light or brightness from a small portion of a subject.
stop down Switching to a higher f-stop, which reduces the size of the diaphragm opening.
telephoto effect The effect a telephoto lens creates that makes objects seem closer to the camera and to each other than they really are.
tonal range The range from the lightest to the darkest tones in an image.
tungsten lighting Common household lighting that uses tungsten filaments. Without filtering or adjusting to the correct white balance settings, pictures taken under this light display a yellow-orange color cast.
underexposure Exposing film or a sensor to less light than required to make an accurate exposure, resulting in a picture that's too dark.
unsharp mask In digital image-editing, a filter that increases the apparent sharpness of the image. The Unsharp Mask filter can't correct an out-of-focus image. See also sharpen.
value The relative lightness or darkness of an area. Dark areas have low values, and light areas have high values.
vignetting Darkening of edges on an image that can be caused by lens distortion, using a filter, or using the wrong lens hood. Also used creatively in image-editing to draw the viewer's eye toward the center of the image.
warm Reddish colors often associated with lower color temperatures. See also Kelvin.
white balance The relative intensity of red, green, and blue in a light source. On a camera, this compensates for light that's different from daylight to create correct color balance.
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Although we usually tend to think of the digital camera as the best thing since sliced bread, there are both pros and cons with its use. Nothing is available on the market that does not have both a good and a bad side, but the key is to weigh the good against the bad in order to come up with the best of both worlds.