Differences between Optical Zoom and Digital Zoom

When you change the focal length of a zoom lens, the subject is magnified. Optical zoom replicates the zoom of a 35mm camera. Digital zoom takes a portion of the image's data and displays it at full size, producing a magnification of the original image, similar to the effect of using a telephoto lens. However, the process is different from the magnification produced using the camera's optical zoom, and the stronger the digital zoom, the more the image will degrade.