More and more camera manufacturers are choosing to label their digital cameras with the total (optical x digital) zoom. This is an unfortunate development and only serves to confuse consumers.
Most people who have used a 35mm camera or an APS camera are aware of only optical zoom. Optical zoom uses the optics (lens) of the camera to bring the subject closer. Digital zoom is an invention of digital video cameras. It is not uncommon to see digital videocams with 300x digital zoom.
For our purpose, digital zoom is not really zoom, in the strictest definition of the term. What digital zoom does is enlarge a portion of the image, thus ‘simulating’ optical zoom. In other words, the camera crops a portion of the image and then enlarges it back to size. In so doing, you lose image quality. If you’ve been regularly using digital zoom and wondered why your pictures did not look that great, now you know.
Is digital zoom therefore all bad? No, not at all. It’s a feature that you might want in your digital camera (in fact, all digital cameras include some digital zoom, so you can’t really avoid it), especially if you don’t care about using (or don’t know how to use) an image editing software. So, as far as digital zoom is concerned, you can do it in camera or you can do it afterwards in an image editing software. Any cropping and enlarging can be done in an image editing software, such as Photoshop.
So, when a digital camera is advertised with 3x digital zoom, no big deal. You can achieve the same 3x (and in fact as much as you want) digital zoom effect in an image editing software. The advantage of doing it later is that you can then decide exactly which portion to crop and how much to enlarge (3x, 4x, …). If you do it in camera, image quality is irreversibly lost.
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