Digital Zoom and Optical Zoom
Most cameras have both optical zoom and digital zoom. Optical zoom works just like a zoom lens on a film camera.
The lens changes focal length and magnification as it is zoomed.
Image quality stays high throughout the zoom range. Digital zoom simply crops the image to a smaller size, then enlarges the cropped portion to fill the frame again.
Digital zoom results in a significant loss of quality as is clear from the examples below.
It’s pretty much a last resort, and if you don’t have it in camera, you can do a similar job using almost any image editing program.
Normal zoom :
Optical zoom 12 X :
Digital zoom 12 X :