Backlighting

Any light coming from behind the subject

Blocked up

A highlight area which is overexposed will have little or no detail. This area is said to be blocked up

Bracketing

Taking multiple photographs of the same scene using different settings

Brightness

Intensity of light energy. The brightness of light is determined by the height of its waveforms - the amplitude of the light vibrations

Catchlight

The lively sparkle of light reflected in a person or animal’s eyes. Quite often reflectors or low-powered pulses of light from a flash unit are used to achieve this effect, since eyes without catchlights tend to look dull.

Chromatic aberration

A common lens flaw which results in loss of sharpness and also in colour fringing - white light having coloured halos (commonly green or purple) around the edges.

Composition

The art of arranging elements of a scene or image in such a way that they are visually pleasing

Contrast

Contrast measures the rate at which brightness values change in an image. As you increase the contrast in an image editing software, the dark colours become darker and the light colours become lighter. Sometimes, by increasing the contrast you can help to bring out details in the image.

Depth of field

The distance range of acceptable focus in front of your lens. When you focus your camera on a given point there is a range in front of the point and behind that point which is also in acceptable focus

Digital

Data consisting of ones and zeroes or any technology based around manipulation of such data

Digital imaging

The use of digital computer technology to create, modify and reproduce visual images.

Digital Zoom

Simulated zoom effects which do not rely on optical lens zooming. Taking a smaller sub-area of the total image area and enlarging it digitally through interpolation. This process does not alter the focal length of the lens

dpi

Dots per inch. A linear measurement of pixel density in computer imaging

Exposure

This is the amount of light that your camera captures while taking a photo. Too much light can create an overexposed image, while not enough light can result in underexposed photographs. An overexposed photograph is lighter than it should be and an underexposed photograph is darker than it should be.

Exposure Meter

Also known as a light meter, it's an instrument used to measure the light intensity – or amount of light - from, or falling on, a subject. From this, the photographer can calculate optimum exposure of the shot, given the film speed and lighting situation.

Field of view

The field taken in by a given lens. Different lenses have different fields of view. Wide-angle lenses take in huge areas of a scene. Telephoto lenses work like telescopes - they narrow down the field of vision considerably so you can take a photograph of a distant object.

Filter

A piece of glass, plastic resin or gelatin that affects the transmission of light and alters the colour of light by blocking the transmission of certain colours

dpi

Dots per inch. A linear measurement of pixel density in computer imaging

Ghost Image

An undesired image captured on a photograph – either a fainter second image of the photo’s subject or an out-of-focus bright light in the field of the optical system. On film, ghost images result from an image being only partially recorded, giving it a translucent, ghost-like appearance, or by using an electronic flash at low shutter speed, thereby capturing a second image by ambient light. In photos taken with a digital camera, ghost images can result when light from the flash hits airborne particles like dust, pollen or moisture.

Graininess

The sand-like or granular appearance of a negative, print, or slide. Graininess becomes more pronounced with faster film and the degree of enlargement.

Hot Shoe

A mounting device, usually built onto the top of a camera, that enables a flash unit, or speedlight, to be mounted on and triggered by the camera.

ISO Speed

How sensitive the image sensor is to the amount of light present. The higher the ISO, the more sensitive the image sensor and therefore the possibility to take pictures in low-light situations.

JPEG

JPEG is a commonly used method of lossy compression for photographic images. The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality..

Juxtaposition

In photographic composition, to juxtapose two objects in a photograph is to place them together, or side by side, to draw comparisons or show the contrasts between them. The contrasts could be tangible, like size, shape or colour, or intangible and abstract, like demonstrating the contrasts between people living in different economic circumstances, for example, by showing a beggar standing next to a wealthy man.

Key Light

Also called the main light, the key light is the principal and brightest light source on a subject, and has the greatest overall effect on the image, highlighting its form and dimension. Outside, sunlight is generally the keylight, while in a studio, stage lights are used.

Lens Speed

The largest lens opening (smallest f-number) at which a lens can be set. A fast lens transmits more light and has a larger opening than a slow lens. Determined by the maximum aperture of the lens in relation to its focal length; the "speed" of a lens is relative: a 400 mm lens with a maximum aperture of f/3.5 is considered extremely fast, while a 28mm f/3.5 lens is thought to be relatively slow.

Micro lens

A lens for close-up photography; designed to focus continuously from infinity down to a reproduction ratio of 1: 2, or with a matched extension ring or teleconverter down to 1: 1; available in normal or telephoto focal lengths to provide a variety of free working distances

Normal lens

A lens that makes the image in a photograph appear in perspective similar to that of the original scene (approximately 45°). A normal lens has a shorter focal length and a wider field of view than a telephoto lens, and a longer focal length and narrower field of view than a wide-angle lens. Normal lenses corresponding to that portion of human vision in which we can discern sharp detail

Overexposure

A condition in which too much light reaches the film, producing a dense negative or a very light print or slide.

Pixelization

The appearance of recognisable square pixels in an image. Pixelization usually occurs when an image has been enlarged beyond the optimal range for its given number of pixels.

Resolution

In digital imaging, it most often refers to the number of pixels per inch in an image file. In traditional photography, if refers to the ability of a lens or photographic material to reproduce small details and is measured in lines per millimeter.

Sepia

A brownish coloured, old-fashioned look to an image, often created as a special effect either within a digital camera or in an image editing software.

Shutter Speed

The length of time that the image sensor is exposed to light – from a few seconds (8 seconds, 2 seconds etc) to fractions of a second (1/125 or 1/500 etc). You need a fast shutter speed to capture action. A slower shutter speed (below 1/125s) are more likely to create blurring from either camera shake or subject movement.

Telephoto Lens

A lens that makes a subject appear larger on film than does a normal lens at the same camera-to-subject distance. A telephoto lens has a longer focal length and narrower field of view than a normal lens.