Glossary "J"

A slang term used to describe the jagged edges created by pixels.

Indicates the energy content of the storage capacitors in an electronic flash. One Joule is the light output given by one watt burning for a second. Therefore a flash unit with a storage capacity of 300 Joules can supply the power to light a 300W lamp for one second. It doesn't take into account any electrical loss between the flash capacitor or flash tube, or the efficiency of tube and reflector.

Standard method of image data compression used to reduce the file size of digital images. It's known as lossy compression because there is a permanent loss of some data during the process.