When I purchased a bridge camera a few years ago as a backup to my DSLR, I had no idea what the difference was between optical & digital camera zoom. Luckily, I decided on the 20x optical with a 4x digital zoom (without really knowing why) rather than the newer model that offered 10x optical and 5x digital zoom.
What’s the difference?
To put it simply, optical camera zoom moves the outer lens closer to the object (as if you had moved that much closer) and brings the image toward you the amount of the camera zoom you have used. With optical zoom, the quality of the image remains the same as if you were shooting without the camera zoom function. The digital camera zoom takes over when you have reached the maximum optical zoom on the camera. The lens does not move any closer to the object, but the sensors choose a focal point and enlarge the image further, much the same way cropping and enlarging with photo editing software does. With digital zoom you will get the same image distortion reduction in image quality, which is why many photographers advise to do your enlarging on the computer where you have the tools to touch up your image.
My Powershot camera has a normal shooting focal length of 5.0 mm. As the lens moves outwards, it brings the image 20x closer or to a setting of 100 mm.
If I continue with the digital zoom, I see the image grow larger in the viewfinder or on the screen up to 4x times more. At maximum optical and digital zoom, I now have a total zoomed image that is 80x’s larger, but the image can appear grainy and slightly out of focus.
Don’t get me wrong, I love the zoom on my camera, both optical and digital. At times when it just isn’t practical to be changing the lens on your DSLR camera, the optical zoom of a point & shoot allows you to get those hard to reach pictures, while the digital zoom gives you a picture when you don’t have the opportunity to get close enough to take that great shot, that might not be the best quality, but still gives you a great photographic memory of the moment and place.