Defining Photography

Useful definitions for amature and beginner photographers.

Photography, like most anything else creative comes with a set of terms, definitions, and processes. Knowing these terms can make a tremendous impact on your skill level and ability to make great photographs. 

Exposure: the quantity of light allowed to act on a photographic material; a product of the intensity (controlled by the lens opening) and the duration (controlled by the shutter speed or enlarging time) of light striking the film or paper. The act of allowing light to reach the light-sensitive emulsion of the photographic material. Also refers to the amount (duration and intensity) of light which reaches the film. In digital photography exposure is the amount and quality of light that is projected on to the sensor.

Overexposure: when too much light reaches the film, or sensor producing a dense negative/image or a very bright/light print. 

Underexposure: whetoo little light reaches the film, producing a thin negative, a dark slide, or a muddy-looking print.

Program Exposure: an exposure mode on an automatic or autofocus camera that automatically sets both the aperture and the shutter speed for proper exposure.

 Aperture: adjustment of the iris, measured as f-stop, which controls the amount of light passing through the lens. Aperture also has an effect on focus and depth of field, the smaller the opening aperture, the less light but the greater the depth of field, that is, the greater the range within which objects appear to be sharply focused. The current focal length divided by the f-number gives the actual aperture size in millimeters.

Aperture Priority: an exposure mode on an automatic or autofocus camera that lets you set the aperture while the camera sets the shutter speed for proper exposure. If you change the aperture, or the light level changes, the shutter speed changes automatically. Apart from the sport or action arena, aperture priority is the most common & effective automatic preference in photography. It can also explained as automatic exposure system in which the lens aperture is set by the photographer, and the camera sets the shutter speed. Can be used in the stop-down mode with any lens that does not interfere with the metering system. 

Shutter Priority: an exposure mode on an automatic or autofocus camera that lets you select the desired shutter speed; the camera sets the aperture for proper exposure. If you change the shutter speed, or the light level changes, the camera adjusts the aperture automatically.

 Shutter Speed: adjustment of the speed (often expressed either as fractions of seconds or as an angle, with mechanical shutters) of the shutter to control the amount of time during which the imaging medium is exposed to light for each exposure. Shutter speed may be used to control the amount of light striking the image plane; 'faster' shutter speeds (that is, those of shorter duration) decrease both the amount of light and the amount of image blurring from motion of the subject and/or camera.

White Balance: on digital cameras, electronic compensation for the color temperature associated with a given set of lighting conditions, ensuring that white light is registered as such on the imaging chip and therefore that the colors in the frame will appear natural. On mechanical, film-based cameras, this function is served by the operator's choice of film, or with color correction filters. In addition to using white balance to register natural coloration of the image, photographers may employ white balance to aesthetic end, for example white balancing to a blue object in order to obtain a warm color temperature.

Colour temperature: description of the colour of a light-source by comparing it with the colour of light emitted by a (theoretical) perfect radiator at a particular temperature expressed in kelvins (K). Thus "photographic daylight" has a colour temperature of about 5500K. Photographic tungsten lights have colour temperatures of either 3400K or 3200K depending on their construction.

ISO: traditionally used to "tell the camera" the film speed of the selected film on film cameras, ISO speeds are employed on modern digital cameras as an indication of the system's gain from light to numerical output and to control the automatic exposure system. A correct combination of ISO speed, aperture, and shutter speed leads to an image that is neither too dark nor too light.

Metering: measurement of exposure so that highlights and shadows are exposed according to the photographer's wishes. Many modern cameras meter and set exposure automatically. Before automatic exposure, correct exposure was accomplished with the use of a separate light meter or by the photographer's knowledge and experience of gauging correct settings. To translate the amount of light into a usable aperture and shutter speed, the meter needs to adjust for the sensitivity of the film or sensor to light. This is done by setting the "film speed" or ISO sensitivity into the meter.

Auto Exposure Bracketing: auto Exposure Bracketing performs automatic exposure bracketing with varied shutter speed and/or aperture.

Bracketing: taking a series of photographs of the same subject at different exposures to insure the "correct" exposure; useful when shooting in situations where a normal metering reading is difficult to obtain. Taking additional pictures of the subject through a range of exposures-both lighter and darker-when unsure of the correct exposure.Some top cameras have provision for automatic bracketing, while manually you can bracket by the use of, say, adjust apertures or shuttle speeds setting or both, manually influent the ASA setting or even adjust the flash output power etc.. 

Artificial light: light from a man-made source, usually restricted to studio photo lamp and domestic lighting. When used to describe film (also known as Type A or Type B) invariably means these types of lighting.

Ambient Light: the available natural light completely surrounding a subject. Light already existing in an indoor or outdoor setting that is not caused by any illumination supplied by the photographer i.e. not by artificial light source.

Diffuse Lighting: lighting that is low or moderate in contrast, for example, an overcast day. 

Backlighting: light coming from behind the subject, toward the camera lens, so that the subject stands out vividly against the background. Sometimes produces a silhouette effect. 

Flat Lighting: lighting that produces very little contrast or modeling on the subject plus a minimum of shadows. 

Incident light: light falling on a surface as opposed to the light reflected by it.

Tungsten Light: light from regular room lamps and ceiling fixtures, not fluorescent. Images produced under this light source can be extremely warm, in fact excessive warmth. Need some color balance filtration or flash to neutralise that.

Bulb Setting [B]:  a shutter-speed setting on an adjustable camera that allows for time exposures. When set on B, the shutter will stay open as long as the shutter release button remains depressed. Another similar option is the "T" setting, where it never drains the battery power on automatic camera body.


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