Optical vs. Digital Zoom
Which is better, a digital camera with 3x optical zoom and 2x digital zoom -- or one with 2x optical zoom and 4x digital zoom?
The answer is easy if you understand the difference
between optical zoom and digital zoom.
With optical zoom, you use the optics of the camera to bring your subject closer, just like in a conventional non-digital camera.
Digital zoom is simply another fancy term to mean "blow up" -- as in "enlarge" -- the actual picture, which therefore always results in a loss of picture resolution. Just as in a film-based picture, enlarging the image magnifies the "grain" of the image, similarly digital zoom 'magnifies' the dots or pixels that make up the digital image (increases the "noise level").
[ Editor's note: In reality, you do not really magnify a pixel, but as you enlarge the image, the gaps between pixels increase and the software 'extrapolates' -- guesses -- what color pixels should fill in the gaps.]
So now it becomes clear that digital zoom is, for comparison purposes , "useless." Why do we say that? Because you would always want the original picture in all its maximum resolution, and then enlarge it, if desired, in an image editing software later.
Is digital zoom then a totally "useless" feature for a digital camera to have? No! Read the above paragraph again: we said, " for comparison purposes ." For arguments sake, let's say that if there is no appreciable loss in image resolution when you use digital zoom, and it helps you in composing a pleasant image, then it is a useful feature to have in your digital camera, and use it by all means. Again, what we are saying is, do not use digital zoom to compare cameras since the same effect can be accomplished in an image editing software.
Bottom line: When comparing digital cameras , always use optical zoom, not digital zoom. And ensure that any digital camera you purchase either allows you to disable digital zoom entirely or warns you clearly that it is switching to digital zoom. "Seamless" optical to digital zoom, without an appropriate warning, is not a good idea.