Optical Zoom
Optical zoom enlarges a distant subject by changing the lens itself, so the picture keeps its real detail.
On this page 3 sections
Optical zoom changes how much of a scene a lens captures by using the lens glass itself. The subject appears larger in the frame while the sensor still records real detail, because the image is formed by light and not by software.
How it works
A zoom lens changes its focal length, the value that sets the angle of view. A longer focal length gives a narrower view and a bigger subject. Cameras with a moving lens barrel do this by sliding glass elements. Many phones instead use a fixed telephoto lens, sometimes folded with a prism, so the zoom comes in set steps and not as a smooth range.
What the numbers mean
- A figure such as 3x shows how much longer the longest focal length is than the shortest one.
- Two lenses with the same multiplier can still reach different distances, because their starting focal lengths differ.
- Digital zoom is a different thing. It crops and enlarges the image, which loses detail.
What it does not promise
A higher zoom number does not guarantee a sharper or brighter picture. Long zoom lenses often let in less light, and they magnify hand shake as much as the subject, so dim light and movement can still blur the result.