| A |
| Active autofocus |
Cameras with active autofocus determines the correct focussing distance by projecting beams of energy - usually infrared or light energy - out to the subject. |
| AE |
Common abbreviation for automatic exposure (AE) |
| AF assist |
A lighting system used to help autofocussing systems achieve focus in low-light conditions |
| Aliasing |
Digital images are based on recording information in discrete steps. If the resolution of an image is not very high then these steps may be noticeable to the human eye. This is aliasing |
| Aperture |
This refers to the camera’s adjustable opening or iris that allows light to reach the camera’s sensor or film. The size of the aperture is measured using an “f-number” also called the “f-stop” (F8, F4.1 etc). The smaller the f-number, the larger the camera’s opening. |
| Aperture priority |
A setting on the camera. In this mode the photographer specifies the desired aperture (see above) and the camera automatically sets an appropriate shutter speed based on the light quality. |
| B |
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 |
| C |
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. |
| D |
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 |
| E |
| 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. |
| F |
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 |
| G |
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. |
| H |
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. |
| I |
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. |
| J |
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.. |
| P |
| 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. |
| S |
| 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. |
