Most people are familiar with the concept of zooming, but I’ve found that few understand the difference between optical and digital zooming. As a result, many travelers are devastated when they come home from a fabulous trip, with highly digitally zoomed photographs, to find them blurry, with the jaggies, and lots of noise.
In optical zooming, the individual pieces of glass (The are the glass elements -seen above in the cutaway view of the lens; the vertical pieces in the photo having convex and concave shapes.) of the lens are mechanically moved to manipulate the image the photographer wants to capture. By realigning the glass elements of the lens, the subject of the image is either magnified or reduced in size, with the angle of view either narrowed or expanded.
When zooming optically, all the magnification or reduction of the subject in the image is manipulated by the lens itself, so that the photograph captured uses the entire sensor area of the digital camera. This is true from the widest angle shot (wide angle focal length) with the least magnification, to the narrowest angle shot (telephoto focal length) with the maximum magnification.