What Does Optical Zoom Mean?
"Optical zoom" refers to the physical zoom abilities of a camera lens, in which the elements of the lens are manipulated to give greater magnification. Optical zoom is preferred to digital zoom, which is simply a cropping of the existing image, rather than a physical magnification.
Zoom Factor
Camera marketers often identify the zoom factor of a lens as a selling point of the camera. For example, a camera may have "5x optical zoom," meaning that the lens itself is capable of magnifying an image five times its original size.
Optical vs. Digital Zoom
"Digital zoom" is a camera-industry buzzword that means the in-camera software can "zoom in" further than the lens is capable, giving the perception of increased magnification. In reality, the camera is simply cropping a smaller portion of the image and interpolating-making up-the detail that is lost in the crop.
Mixed Zooms
Some cameras have both optical and digital zoom, often denoted by the manufacturer as something like "5x optical / 10x digital zoom." This means that the cameras lens can provide 5x magnification, and if more zoom is needed, the camera's software takes over and crops the image.
Advantages
Optical zoom retains the full resolution power of the lens. Digital zoom is essentially the same as cropping the image after the fact in a photo editing program. You don't actually gain detail; you simply make the details you have take up more of the image. A small degree of digital zoom won't hurt your picture quality, but too much will make your images choppy and "pixelated."
Alternatives
When photographing a bride and groom at the altar or a hungry crocodile, some type of zoom is obviously necessary. But in most situations, the best option for quality pictures is to get closer to your subject. Not only will the image quality be greater, you'll interact more with the people and things in your photographs.
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