Optical Zoom vs. Digital Zoom (Page 2 of 3)

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by Chris Miller February 9, 2007 02:02 PM

Categories: Digital and SLR Cameras Camcorders

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For example, let’s assume that you’re pointing your camera at the outside of your house. Now let’s say that you want to zoom in on one of the house’s windows using digital zoom. As you zoom in, the image inside the camera is completely unchanged. Your sensor chip still sees the entire house because the lens hasn’t changed the image. However, the sensor chip creates a zoom effect by discarding sensor information that doesn’t pertain to the window. If the window makes up 5% of the total house image, then the sensor chip will only use 5% of its individual photosites to capture the image, ignoring the other 95%. The result is a zoomed in image that is much lower resolution because it’s using only a small area of the sensor to capture the image.

A Question of Quality

So what does all this zooming do to the quality of your pictures? Let’s take a look at some pictures to see what actually happens. We start with a rather dull image of a school that is zoomed out.

If I wanted to zoom in on the flag in the upper right, I could either zoom in using optical zoom or digital zoom. Let’s begin with an optical zoom. In this next picture, I changed the zoom level using only the lens. My sensor chip still used its entire surface area to capture the picture.

Notice that the image is still pretty clear and smooth. You can’t really see the individual dots that make up this image.

Now let’s see how a digital zoom would fare. Again, I’m beginning with the view of the entire school and trying to zoom in on just the flag. In this case, however, I’m using digital zoom, not a lens-based optical zoom.