What does Optical Zoom mean when talking about photography?

When talking about photography the term ‘optical zoom’ refers to a specific type of lens which allows a photographer to alter the magnification ratio by changing the distance between groups of optical elements within the lens. The zoom ratio of an optical zoom lens is often controlled by rotating the front portion of the lens, this manipulates a mechanism within the lens which moves elements within the lens barrel. On smaller cameras the zoom ratio may be controlled electronically using a motor. Importantly, the focus settings of a lens are not effected by changes in the lenses magnification ratio, allowing changes in magnification to b made after focus has been set.

An optical zoom lens.
Photo: Dan Carr