What is Optical Zoom?
Optical zoom is the achieved by using your camera’s zoom lens. Optical zoom is the increase in the focal length of your zoom lens. The focal length is basically the magnification of a subject. Focal length is represented in millimeters (mm) and is used to describe the camera lens.
Focal length is not a measurement of the length of a zoom lens, it’s a calculation of the optical distance where light rays converge to create a sharp image of a subject and the digital sensor in your the camera. Focal length is determined when the lens is focused at infinity. It also represents the angle-of-view (which narrows as you zoom in). Generally, the longer the focal length, the narrower the angle-of-view along with greater magnification of your subject.
What is Digital Zoom?
Digital zoom, on the other hand, is an internal process that enlarges an image once it has been captured by the digital camera’s sensor. Different images can be created of the same subject simply by adjusting the zoom. For a refresher on the concepts behind this, check out our lesson on Exposure: Lenses, Aperture and Shutter Settings.
Go outside with a friend and your optical zoom, get some distance between you, use your camera and zoom in as far as you can, taking a closeup of her face.
Now slowly move closer, zooming out and keeping her face the same size in each picture you take. Repeat with a full length shot of your friend. How did the relationship between the background and foreground change?