Optical zoom
Optical zoom is a camera function that enables you to enlarge a subject by physically moving the camera lens. When you optically zoom, the lens either moves inward or outward to move the object nearer without changing the picture quality. This process is similar to how binoculars or a telescope works — the farther the lens moves, the better you can see the faraway object. Optical zoom is commonly present in advanced smartphones such as iPhone Pro versions or Samsung Galaxy S models, and in expert-level cameras such as DSLRs. The greatest benefit of optical zoom is that image quality is never lost since the object naturally appears closer. For instance, if your phone boasts a 5x optical zoom, it is interpreted that the lens can zoom in an object five times closer without losing any sharpness and detail. Photographers like optical zoom for wildlife, sports, and landscape photography since it provides crystal-clear photographs even at great distances. In other words, optical zoom is actual zoom since it adjusts the lens position to take a closer and clearer photograph. It is hardware-based, hence costly, but provides the best output when quality is most important.
Digital Zoom
Digital zoom is quite different from optical zoom. Rather than moving the lens physically to bring the object nearer, it magnifies an area of the image by clipping it and stretching out the pixels to expand it into the frame. This is achieved by software, not by the lens, so the further you zoom, the worse the image quality. It gets grainy, out of focus, or pixelated. Digital zoom is ubiquitous on most low-cost smartphones and video calling applications since it doesn’t need any sophisticated lens system. It’s similar to zooming in a photo after capturing it — you see what’s closer, but you lose detail and sharpness. For instance, 10x digital zoom may sound impressive, but all it does is mean that the software is magnifying the center of the image 10 times over, usually resulting in a blurry mess. Digital zoom is useful when you are just looking for a quick close-up without getting up, but it isn’t good for professional or crisp photography. Most phone companies promote large digital zoom figures, but the quality of the image does not increase. In short, digital zoom is fake zoom — simple to implement, but it compromises on image sharpness and resolution along the way.