an image file format that allocates 8 data bits to record light intensity for each color channel of each pixel. An 8-bit image can record 256 levels of brightness. Most JPEG, TIFF, PNG, and other common image file formats are 8-bit images. Sometimes called a 24-bit image. The number 24 comes from counting 8-bits in each of the three color channels.

an image file format that allocates 12 data bits to record light intensity for each color channel of each pixel. A 12-bit image can record 4096 levels of brightness. The native Raw file formats of many digital cameras record 12-bit images. These images usually must be converted to 8-bit images for printing and other uses.

an image file format that allocates 16 data bits to record light intensity for each color channel of each pixel. A 16-bit image can record 64K (65,536) levels of brightness. The native Raw file formats of some digital cameras record 16-bit images. These images usually must be converted to 8-bit images for printing and other uses. Also called a 48-bit image. The number 48 comes from counting 16-bits in each of the three color channels.

an image file format that allocates 32 data bits to record light intensity for each color channel of each pixel. A 32-bit image can record a huge brightness range. None of the current digital cameras are capable of recording 32-bit images. Instead, they are created by merging multiple 8-bit images into a single image with an extended dynamic range.

a lighting scheme in which the photographer adds light sources to illuminate the subject. The opposite of subtractive lighting.

the exposure setting that controls how much light can pass through the lens at any given instant. The aperture is adjustable by means of a diaphragm that you can partially close restrict the amount of light that can pass through. Apertures are expressed as f-numbers, with the smaller numbers (f−4) designating a wider aperture opening and larger numbers (f−22) designating narrower aperture openings.

the automatic exposure mode that allows the photographer to select the aperture while the camera adjusts the shutter speed depending on the light level. Compare to shutter-priority exposure.

a light metering mode that averages the light intensity across the field of view of the lens.

when the background is brighter than the subject itself, usually because the primary light source is behind the subject.

a light used to illuminate the background in a studio photograph. The background light is usually positioned so that it does not illuminate the primary subject.

directing a flash or other light toward a ceiling or other surface instead of directly at the subject.

take multiple pictures of the same scene at slightly different exposures and choose the best one later.

the difference in the brightness of the darkest shadows and brightest highlights. Also called dynamic range.

an image file containing minimally processed image data from the camera's digital image sensor, recorded in the camera manufacturer's proprietary file format. Raw files are usually 12-, 14-, or 16-bit images that must be processed and converted to another format for use.

motion of the camera during the exposure causing a blurred image.

the highlight in the eye of a portrait subject, usually caused by the eye catching a reflection of one of the studio lights.

the tendency for the human eye and brain to automatically adapt to changing lighting conditions, adjusting color perception so that most changes in light source color go unnoticed.

a term used to define depth of field. Points of light that are closer or farther away than the focus point of a lens are blurred into disc shapes instead of single points. The edge of such a disk is known as the circle of confusion. Depth of field is the zone in which the circle of confusion is small enough that the average human eye can't perceive the difference between the disk and a single point.

a measure describing the color makeup of a light source. Color temperature is defined as the light that would be radiated by a theoretical black body heated to a given surface temperature. Color temperature is measured on the Kelvin temperature scale. For example, the warm light of an incandescent lamp has a color temperature of 3400 kelvin and the cool light of a north sky is approximately 7500 kelvin.

photographic lights that give off less heat than incandescent lights. Cool lights usually use specially color corrected fluorescent lamps.

the area in a lens' field of view where objects appear acceptably sharp. Objects within the depth of field zone appear sharp while objects outside the depth of field appear visibly blurred. Also see circle of confusion.

a lighting accessory, composed of translucent material, that is used to diffuse and scatter the light to achieve a softer effect. The diffuser may be attached to the lighting instrument or placed between the light source and subject.

the light sensing component of a digital camera.

an artifact of the digital image sensor and its processing software that shows up as grain-like speckles scattered throughout the image. Higher ISO settings exaggerate noise.

the light emitting characteristic of certain lights, such as mercury vapor and sodium vapor, that produce large quantities of light within one or more narrow wavelength bands and very little light throughout the rest of the visible spectrum. This contrasts with the more uniform light distribution of sunlight and incandescent lights.

the difference in the brightness of the darkest shadows and brightest highlights. Also called brightness range.

any light that adds an effect (such as the highlight on the hair in a portrait) instead of being part of the primary lighting for the scene.

any of the multiple combinations of aperture, shutter speed, and ISO that all produce the same exposure. A larger aperture paired with a faster shutter speed can deliver the same total amount of light to the image sensor as a smaller aperture paired with a slower shutter speed.

a numeric scale for measuring exposure in which each EV unit increases or decreases the exposure by a factor of 2 (doubling or halving the light). Equivalent exposures (combinations of aperture and shutter speed that result in equal exposure) all have the same EV number. EV was developed for use in exposure tables to calculate exposure, but now it's used primarily as a unit of measurement for exposure compensation.

a camera setting that allows you to increase or decrease the exposure calculated by the camera's automatic exposure system.

the combination of aperture, shutter speed, and ISO that controls the amount of light reaching the digital image sensor.

a secondary light used to fill in the shadows cast by the main light and increase overall illumination.

using a photographic flash as a fill light to open up the harsh shadows cast by direct sunlight.

a light meter designed to read the light from a photographic flash and calculate the correct exposure.

synchronizing the triggering of the flash with the opening and closing of the shutter.

a photographic light source of extremely high intensity and short duration. Examples of flash lighting range from the small built-in flash units incorporated into most cameras to large studio lights. Because of the short duration of the light, flash is unsuitable for video and motion picture lighting, but it works great for most film and digital still photography.

a transparent colored material used to filter the color of a light. The term is short for gelatin, the material originally used to make the filters, but most gels are made of acetate and other plastics today.

a standardized reference target for light meter readings and white balance. The standard gray card is a neutral gray that reflects 18 percent of the light falling on it — the same reflectance as the theoretical "average" scene for which all light meters are calibrated. Since it's neutral gray, it can also be used for custom white balance.

1) a structure suspended from the ceiling of a studio to provide attachment points for suspending overhead lights. 2) a lighting accessory that is attached to a light to restrict its spread. Also called a honeycomb.

a light placed above and slightly behind a portrait subject to create a highlight across the head and shoulders.

any point source light that creates sharp highlights and hard-edged shadows.

an image with an extreme brightness range, recorded as a 32-bit image.

a photograph composed mostly of very light tones. Compare to low key.

an important and useful tool for evaluating exposure. It plots the distribution of tones in an image as an area chart, with the range of values from dark to light going from left to right along the base of the chart and the prevalence of a given value represented as height.

a type high-performance, continuous output lighting with daylight color balance. HMI lights have twice the light output of comparable quartz or tungsten lights, and generate less heat, but they're very expensive and require bulky ballast/transformers and long warm-up times. They're used primarily by big-budget film and video productions.

photographic slang for incandescent lights, so named because they generate a lot of heat, especially the high-output lights found in photography studios.

the mounting point on a camera for an accessory flash unit. It includes electrical contacts that trigger the flash to fire in synchronization with the shutter when you take a picture.

the focus point at which the farthest reaches of depth of field extends to infinity.

a technology built into some lenses (and cameras) that counteracts camera shake to produce sharp images at slower shutter speeds than would otherwise be possible.

any light in which the light is produced by passing electrical current through a filament. Contrast to fluorescent lights, which produce light by exciting a gas.

a meter that measures the brightness of the light falling on the subject instead of reflected from it.

a law of physics that states that the intensity of light is inversely proportional to the square of the distance from the source. So, doubling the distance between a light source and the subject reduces the light intensity to one fourth.

a number indicating the relative sensitivity of the image sensor (or film) to light. A higher ISO indicates greater sensitivity (and increased digital noise).

the temperature scale used for color temperature readings.

the primary, dominant light that defines the shape and shading on the subject. Also called the main light.

an accent light used to create highlights to complement those from the main light.

an instrument for measuring light levels and calculating exposure. May be a separate hand-held tool or built into a camera.

the ratio between the brightness of the highlights and shadows in a given scene, usually a portrait.

a photograph composed mostly of very dark tones. Opposite of high key.

a numeric scale representing the brightness of the light reflected from the subject. It's the same kind of scale as EV, but measures subject luminance rather than exposure. The LV for a gray card in mid-day sun is LV15.

the primary, dominant light that defines the shape and shading on the subject. Outdoors, the main light is usually the sun. Indoors, it's usually the brightest light — the one that provides the principal illumination for the scene. People with a background in film and video lighting usually call this a key light, but I prefer the term main light.

another name for multisegment metering mode.

a scene illuminated by a mixture of lights. The mixture might include ambient light and light supplied by the photographer and/or a mixture of different kinds of lights, such as daylight, fluorescents, incandescents, flash, and others.

a low-power incandescent light added to a photographic flash to aid in positioning the lights. You use the modeling light as a preview and the flash for the actual exposure.

a light metering mode that samples light intensity at numerous locations across the image and calculates the best exposure for the brightness range it finds. This feature goes by several names, such as matrix metering. Also called Matrix metering mode, ESP metering, and other brand names.

a scene that is shaded from the direct light of the sun but lit by a large expanse of open sky.

too much light reaching the sensor, resulting in an image that is too light overall.

a high-output tungsten light bulb made for photographic lighting. It looks like an oversized household light bulb.

preprogrammed camera settings for various common photographic situations, such as scenery, portraits, or sports action. The program presets the camera's automatic exposure mode, ISO setting, and white balance to what the camera manufacturer deems appropriate for the subject. Also called scenes by some camera makers.

a high-output, tungsten-filament, incandescent light. These lights are better suited to photographic use than standard household lamps because they have higher light output and more consistent color temperature.

the principle that states that there are multiple combinations of aperture, shutter speed, and ISO that all produce the same exposure. See equivalent exposure.

a light meter that reads light levels of the light reflected from the subject.

a light reflecting surface. 1) the bowl-shaped surface surrounding the lamp of a photographic light that helps direct the light toward the subject. 2) a white or silver board or other portable reflective surface used to reflect light from a source onto the subject. Note that the color of the reflector affects the color of the light it reflects. A white or silver reflector reflects white light. A gold reflector, on the other hand, gives the reflected light a warm golden glow, and a blue wall gives the reflected light a cool blue cast.

see programmed exposure modes.

controls how long the image sensor is exposed to the light coming through the lens. Exposures are normally measured in fractions of a second and controlled by an electronically controlled shutter in the camera. For convenience, camera controls normally list only the denominator of the fraction, so a shutter speed of 500 is really 1/500 of a second.

the automatic exposure mode that allows the photographer to select the shutter speed while the camera adjusts the aperture depending on the light level. Compare to aperture-priority automatic exposure.

a flash unit that is triggered by a light sensor detecting light from another flash unit. There is no need for a sync cord connecting the slave flash to the camera.

any light that creates diffuse highlights and soft-edged shadows. The effect is usually the result of a large natural light source, such as a large northfacing window, or a hard light that has been softened by bouncing and/or diffusing the light.

light that spreads or bounces beyond the subject at which the lighting instrument is pointed.

a lighting instrument that uses a shaped reflector and/or a lens system to achieve a focused beam of light. Spots produce a hard light and may be used with cookies and gobos to create shadow pattern effects.

a reflective light meter with a very narrow angle of view (usually about two degrees).

photographic slang for one EV unit. The term originated from the detents, or click stops, on the shutter speed dials and aperture rings of manual cameras and lenses. The detents were spaced in one EV increment.

another name for a photographic flash lighting instrument. Normally used to refer to large studio lighting equipment as opposed to a small battery-powered accessory flash unit attached to a camera.

a lighting scheme in which the photographer uses shades and diffusers to block or reduce the light falling on the subject. The opposite of additive lighting.

the exposure guideline which states that the correct exposure for an average subject in direct mid-day sun is equal to f−16 at a shutter speed equal to the reciprocal of the ISO rating. For example, at ISO 100, the exposure is 1/100 at f−16.

a small cable that connects a camera to an external flash unit and triggers the flash to fire in synchronization with the shutter when you take a picture. Not needed with on-camera flash units attached to the camera's hot shoe.

a lighting technique used to photograph highly reflective subjects such as silverware. The subject is completely surrounded by a "tent" of translucent white diffusion material. The lights are placed outside the tent and the camera lens is inserted through a small slit.

a hypothetical construct used in calculating color temperature. It closely approximates the light emitting characteristics of both the sun and the filament in an incandescent light bulb.

an incandescent light that uses a tungsten filament. Most standard household lights, photofloods, and quartz lights use tungsten filaments.

too little light reaching the sensor, resulting in an image that is too dark overall.

setting the camera to match the color temperature of the light source so the finished images will have the correct color.

a device for triggering a flash unit or camera remotely without wires or mechanical connections. Most devices employ radio-frequency (like garage door openers) or infra-red (like TV remotes) signals. Compare to slave flash.

a system for visualizing and controlling how the brightness range of a scene will render as a range of values in a photographic print. The Zone System was developed in 1940 and popularized by Ansel Adams. It's built around a gray scale in which the steps, called zones, are each twice as reflective as the next darker step.

the Zone System step that corresponds to middle gray — the same 18 percent reflectance as a gray card.