Glossary of common photographic terms

I’ve written this list to help avoid misunderstandings of definitions across my site & when entering in to discussions. If you think I need to add some more, please let me know.

AE Auto Exposure. A system by which the camera can estimate & set the level of exposure required.

AF Auto Focus. A system that allows the camera to set the lens focus point suitable to subject distance.

Angle of View The angle formed between imaginary lines drawn from the extreme sides of an image formed by a camera / lens combination. Can be given for horizontal, vertical or diagonal planes.

Aperture The size of opening formed by the camera iris to allow light through.

AV Aperture Priority mode. A mode that sets the aperture at a fixed size and allows an auto exposure camera to adjust exposure by varying other settings such as shutter speed.

Bracket The process of taking several exposures with different settings, so as to maximise the potential for a perfect image. Eg Exposure Bracketing

Bulb setting A setting which allows long exposures (over 30s) to be made.

Circle of Confusion The series of small circles of light that can be considered to form an image. The smaller the circle, the sharper the image.

Colour Temperature A way of defining the overall colour of a light source. Often quoted in Kelvins.

Contrast The difference in brightness value of different points within an image. The greater the difference, the greater the contrast.

Crop Factor In DSLRs, the amount by which an image is apparently cropped in comparison to the same lens image on a full frame 35mm SLR. This is due to smaller sensor sizes in some DSLR cameras.

Depth of Field The distance between the nearest and furthest points that are in acceptable focus at any given lens setting.

Exposure The amount of light allowed on to the recording medium to record an image. Often quoted as a period of time at specific settings.

Exposure Compensation Changing the calculated correct exposure to compensate for some factor that may affect the final image quality; such as highly reflective snow.

F-number The setting of aperture size. A higher f-number equates to a smaller aperture.

Focal Length The length (usually in mm) at which a lens system brings light from infinity to a focused point. A longer lens (greater focal length) will appear to bring the subject closer to you than a shorter lens.

Hyperfocal Distance The distance at which a lens must be focused, for everything from half that distance to infinity to be in acceptable focus.

ISO International standards organisation definition for the light sensitivity of film & sensors. A higher number equates to a higher sensitivity.

Prime A lens with a fixed focal length

Standard Lens A lens with a focal length and field of view similar to that of a human eye. About 50mm focal length on a 35mm camera.

Telephoto A lens with a greater than standard focal length, often used to bring the subject closer.

TV Shutter speed priority. A mode that fixes the shutter speed and allows the camera to adjust exposure by changing other settings, such as aperture.

Wide-angle A lens with a shorter than standard focal length, giving a wide field of view, often used for Landscapes.

Zoom A lens with a variable focal length. Versatile but often heavier & more expensive than a prime, for any given image quality.