Glossary of Terms

High key image – an image consisting almost exclusively of light tones.

Highlight – the brightest part of an image, particularly when specular or causing notable over-exposure.

Histogram – in digital photography, a statistical representation of the number of pixels of a particular value plotted against the range of possible values.

Hot-shoe – a reasonably standardized connector found on the top of a camera designed to link with electronic flashguns.

Hue – the perceived colour of light, for example red or blue. Hue varies with wavelength. Colour is characterized by hue, saturation and lightness.

Hunting – the action of an autofocus lens which is, for one of a variety of reasons, unable to achieve a point of sharp focus. This may occur when the contrast or light level is low. Lens focus shifts continually, or hunts, between distant and close-up limits.

Hyperfocal distance – the shortest distance from a lens to an in-focus subject, for a particular aperture, when the lens is focused at infinity. When set to the hyperfocal distance depth of field extends from about half the hyperfocal distance to infinity.