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Sunday, April 12, 2009

AE : Automatic Exposure metering, i.e. the camera measures the light and sets shutter speed and aperture (either or both).
AE lock (AE-L) : Locks an automatic exposure setting in the camera’s memory.
AF: Auto-focus.
AF lock (AF-L): Locks an auto-focus lens at its present focus distance.
Aliasing : The jaggy edges that appear in bitmap images with curves or lines at any angle other than multiples of 90°.
Angle of view : The extent of the view taken in by the lens.
particular format size : The angle made at the lens across the image diagonal.
Aperture (of lens) : Size of the lens opening through which light passes. The relative aperture is calibrated in f-numbers, being the diameter of the beam of light allowed to pass through the lens, divided into its focal length.Widest relative apertures therefore have the lowest f-numbers. All lenses set to the same f-number give images of a (distant) scene at equal brightness.
ASA : Stands for (obsolete) American Standards Association. The initials were once used for a film speed rating system. Now replaced by ISO.
Aspect ratio : This is usually found in dialog boxes concerned with changes of image size and refers to the relationship between width and height of a picture. The maintaining of an image’s aspect ratio means that this relationship will remain the same even when the image is enlarged or reduced.
Auto-focus (AF) System : by which the lens automatically focuses the image of a selected part of your subject.
Av Aperture value : AE camera metering mode by which you choose aperture, and the metering system sets shutter speed (also called aperture priority).
‘B’ setting Brief or bulb :On this setting the camera shutter stays open for as long as the release button remains depressed.
Bit : Stands for ‘binary digit’ and refers to the smallest part of information that makes up a digital file. It has a value of only 0 or 1. Eight of these bits make up one byte of data.
Bitmap or ‘raster’ The form in which digital photographs are stored, made up of a matrix of pixels
Bracketing (exposure) : Taking several pictures of your subject at different exposure times or aperture settings, e.g. half and double, as well as the estimated correct exposure.
Brightness range : The range of brightnesses between shadow and highlight areas of an image.
Byte : This is the standard unit of digital storage. One byte is made up of 8 bits and can have any value between 0 and 255; 1024 bytes equal 1 kilobyte; 1024 kilobytes equal 1 megabyte; 1024 megabytes equal 1 gigabyte.
CCD : Charge-Coupled Device. Electronic light-sensitive surface, digital replacement for film.
Close-ups : Photographs in which the picture area is filled with a relatively small part of the subject (e.g. a single head). Usually photographed from close to the subject, but may be shot from further away using a long focal length lens.
Color balance : A color photograph that closely resembles the original subject appearance is said to have ‘correct’ color balance. Mismatching film type and lighting (wrong color temperature) gives a cast most apparent in gray tones and pale tints.
Color mode : The way that a digital image represents the colors that it contains. Different color modes include Bitmap, RGB and Grayscale.
Color temperature : A means of describing the color content of a ‘white’ light source. Based on the temperature (absolute scale, expressed in kelvin) to which a black metallic body would have to be heated to match the light, e.g. household lamp 2800 K, photoflood 3400 K.
Composition : The activity of positioning the various subjects in a picture within a frame or viewfinder. Photographers often aim to create a visual balance of all the elements within their photographs. They do this via careful composition.
Depth of field : Distance between nearest and furthest parts of the subject sharply imaged at the same time. Greatest with small lens apertures (high f-number), distant scenes and shortest focal length lenses.
DIN : Stands for Deutche Industrie Norm (German Industrial Standard). DIN numbers denoted a film’s relative sensitivity to light. Halving or doubling speed is shown by decrease or increase of the DIN number by three. Now incorporated in ISO and distinguished by degree symbol.
DPI : Dots per inch, a term used to indicate the resolution of a scanner or printer.
Dynamic range : The measure of the range of brightness levels that can be recorded by a digital sensor.
Filter : lens Sheet of (usually dyed) gelatin or glass. Used over the camera or enlarger lens mainly to reduce the light (neutral density gray filter) or to absorb particular wavelengths from the light beam.
Fixed focus : Camera lens set for a fixed subject distance. Non-adjustable.
Flare : Scattered light that dilutes the image, lowering contrast and seeming to reduce sharpness. Mostly occurs when the subject is backlit.
Flash : electronic Equipment that gives a brief, brilliant flash of light by discharging an electronic capacitor through a small, gas-filled tube. Given time to recharge, a unit gives many thousands of flashes, usually triggered by contacts within the camera shutter.
Focal length : In a simple lens the distance (typically in millimeters) between the lens and the position of a sharp image for a subject a great distance away. A ‘normal’ lens has a focal length approximately equivalent to the diagonal of the picture format it covers, i.e. 50 mm for 36 mm × 24 mm.
Grain : Irregularly shaped, microscopically small clumps of black silver making up the processed photographic silver halide image. Detectable on enlargement, particularly if the film emulsion was fast (ISO 1000 or over) and overdeveloped. Hard grade paper also emphasizes film grain.
Guide number (flash factor) : Figure denoting the relative power of a flash source. The GN is the light-to-subject distance (usually in meters) multiplied by the f-number for correct exposure, e.g. GN of 16 = 2 m at f8 or 1 m at f16. (Unless film speed is quoted, factor refers to ISO 100 film.)
Histogram: A graph that represents the distribution of pixels brightness within a digital image.
Interpolation: This is the process used by image editing programs to increase the resolution of a digital image. Using 'fuzzy logic' the program makes up the extra pixels that are placed between the original ones that were generated at the time of scanning or capture.
ISO : International Standards Organization. In the ISO film speed system, halving or doubling of speed is denoted by halving or doubling number. Also incorporates DIN figure, e.g. ISO 400/27° film is twice as sensitive as ISO 200/24°.
JPEG : A file format designed by the Joint Photographic Experts Group that has inbuilt lossy compression that enables a massive reduction in file sizes for digital images. Used extensively on the web and by press professionals for transmitting images back to newsdesks worldwide.
Megapixel : One million pixels. Used to describe the resolution of digital camera sensors.
Montage : An image constructed by combining what were originally several separate images.
Pattern (composition) : Repeating subjects that have similar characteristics such as color, shape and texture create a strong visual element that is often referred to as pattern. Pattern can be used in a similar way to tone, line and color as a way to balance compositions and direct the viewer’s eye throughout the frame.
Pixel : Short for picture element, refers to the smallest image part of a digital photograph.
Polarizer : Gray-looking filter, able to darken blue sky at right angles to sunlight, and suppress reflections from (non-metallic) surfaces at angles of about 30°.
‘Red eye’ : The iris of each eye in portraits shows red instead of black. Caused by using f lash directed from close to the lens.
Through-the-lens (TTL) metering Measuring exposure by a meter built into the camera body,which measures the intensity of light passing through the picture-taking lens.
Tv Time value : AE camera metering mode by which you choose shutter speed and the metering
system sets aperture (also called shutter priority).