It was suggested that we should put together a photographic glossary of useful terms. I have taken on the task of creating this list and have great pleasure in posting part 1. Part 2 to follow below.
AdobeRGB
Colour space recommended by Adobe Systems, Inc. for commercial printing. It offers a wider range of colour reproduction than sRGB. When images using AdobeRGB are opened by non-compatible software, the colours look lighter.
Auto Exposure (AE) Metering
The brightness of the subject is measured by the camera and these measurements are then used automatically by the camera to set the exposure. Some typical metering modes are Multi segment Metering, Centre weighted metering, and Spot Metering.
Aperture
The “hole” in the lens that lets the light through. The aperture increases or reduces the size of the light beam that comes through the lens. The bigger the hole, the more light comes through. See also f-number.
Aperture Priority
A mode of operation where the photographer has control over the aperture of the lens. The photographer manually selects the aperture and the camera then automatically sets an appropriate shutter speed to give the correct exposure. This is most often used when the photographer wishes to control the depth of field in the resulting picture.
Auto Bracket
A mode of operation that automatically changes the exposure of the picture being taken. Typically, when the shutter button is pressed, three images are shot. The first one has no compensation, the second is under exposed and the third is over
exposed. The order and extent of under/over exposure can usually be varied.
Camera Shake (Blur)
If the camera moves while the shutter is open, the entire image appears blurred. This occurs more often when shutter speed is slow. Some ways to reduce camera shake are:
using the flash, raising the shutter speed or alternatively, use a tripod/monopod to stabilize the camera. Because camera motion causes camera shake, if your (SLR) camera has a mirror lock-up facility, this can be used to reduce blur. As a general rule, if you are an dSLR user, the shutter speed should not be lower than 1/(focal length of lens x digital sensor crop factor). If you are using a camera with a 1.5x crop factor and a 50mm lens, the shutter speed should ideally not be set to less than 1.5x50=1/75th of a second in order to minimise blur.
Centre Weighted
A metering mode where the camera measures the light entering the camera and is strongly influenced by the amount of light in the centre of the image. It measures the light intensity over the whole image but biases the exposure to try and get the centre of the image correctly exposed.
Colour space
A defined range of colours from the spectrum which are used. In digital cameras, sRGB is defined as the standard by the Exif format. AdobeRGB is also used, generally for commercial printing.
Colour Temperature
The colour of the light source illuminating the subject. This is usually indicated in absolute temperature, using the Kelvin (K) scale. The colour of light shifts to a bluish colour as the colour temperature rises, and to a reddish colour as the colour temperature falls.
Crop Factor
The sensors used in dSLR are often a different size (smaller) to a 35mm film frame. The focal length of the lens being used determines the size of image that the lens projects onto the sensor. As the digital sensor is sometimes smaller than the film frame, the lens only projects the middle part of the image onto the sensor and the outer parts of the image “fall off the edges” and are lost. This gives the effect of using a longer focal length of lens. Typical digital sensor crop factors are 1.5x or 1.6x. A 50mm lens used on a digital camera with a 1.5x crop factor will give a similar view to a 75mm lens used on a 35mm film SLR.
Depth of Field
The area of acceptable focus extending in front of, and behind, the exact point of focus of the lens. Reduce the aperture (use a bigger f-number) to increase the depth of field.
EV (Exposure Value)
Traditionally used on hand-held exposure meters. The Exposure Value is a figure used to represent a particular intensity of light. The measured EV can be used to determine a particular shutter speed and aperture setting. A given EV can be satisfied by a large number of equivalent shutter/aperture combinations. See the “manual exposure, juggling three balls” sticky thread
http://www.worldphotographyforum.com...read.php?t=125 for more explanation. Exposure Values may typically range from EV1 (satisfied by 1 second, f/4, ISO 800) to EV18 (satisfied by 1/4000th second, f/5.6, ISO 50).
Exposure Compensation
The process of changing the shutter speed and aperture value to vary from the figures suggested by the camera’s meter measurements. A camera’s meter is calibrated to give the correct exposure for a mid tone grey surface for a given amount of light being reflected from it. The camera does not know if the reading it has taken is due to a large amount of light being reflected from a very dark surface, or a small amount of light being reflected from a light surface. The camera will hedge its bets and plump for grey in either of these extreme situations. Exposure compensation is used to adjust for this kind of situation.
EXIF (EXchangeable Image file Format for digital still camera)
A standard digital camera file format established by the Japan Electronics and Information Technology Industries Association (JEIDA).
f-number
The number resulting when the focal length of a lens (in mm) is divided by the diameter of the aperture (effectively how big the hole is in mm). The sequence of f-numbers is used to calibrate the aperture in regular steps, known as f-stops. F-numbers traditionally followed a sequence where each stop represented a halving or doubling of the amount of light the aperture would let through. Modern lenses will often now increment in one half or one third stop steps. As the f-number is a ratio of focal length to aperture, the f-number becomes progressively bigger as the aperture becomes smaller to allow in less and less light. A lens with a small f-number is often called a “fast” lens because it allows a faster shutter speed to be used for any given Exposure Value.
Histogram
A graph that shows the darkest and brightest points in an image. The horizontal axis represents the brightness and the vertical axis represents the number of pixels present in the image at that particular brightness.