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Old Jul 27, 2004, 2:53 PM   #1
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What exactly is digital zoom and is it really worth it?

Is digital zoom the same as simply blowing up a pictre with paint, where image quality is lost as each pixel is enlarged, or is it quite different?
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Old Jul 27, 2004, 3:50 PM   #2
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Digital Zoom is simply cropping an image (taking the center portion of it out, then discarding the remainder, to make it look like more optical zoom was used).

It then takes this smaller center portion of the image, and enlarges it using interpolation, back up to the original image resolution.

This interpolation process adds pixels to the image to enlarge it, based on the values of adjacent pixels. However, interpolation can only add pixels, and does not increase the detail that was present.

So, quality degrades rapidly, as more Digital Zoom is used, since you only have as much detail as was present in the crop of the image (actual number of pixels captured by the camera to represent your subject).

You can accomplish the same thing later with software - -with more accuracy for the crop, using better interpolation techniques than you'll find in the camera.

I keep Digital Zoom disabled on my camera.


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Old Jul 27, 2004, 4:01 PM   #3
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P.S.

For better quality enlargements, use a product with better interpolation algorithms. I use the Lanczos based algorithm in a free image editor called Irfanview. You can download from http://www.irfanview.com

Make sure to download the free plug-ins, too.

To interpolate an image, go to "Image", "Resize/Resample", then select the Lanczos Filter option. You can specify the amount of enlargement needed.

However, you cannot crop an image as much as you think. Because resolution is computed by multiplying width x height, if you crop an image to make it look you used twice as much optical zoom, you end up with an image size that's only 1/4 the original resolution.

Sure, you can interpolate back up to it's original size, but you're only adding pixels, based on the values of adjacent pixels. You're not adding any more detail than was captured by the camera's sensor to begin with.


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