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Old Dec 5, 2005, 10:30 AM   #1
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Way back when I bought my first digicam (Nikon CoolPix 950), I remember frequenting Steve's site and his linked sites. I know that digital zoom ain't worth spit, but I do remember reading one page back then that had a cleaver idea. It went something like this...

<paraphrase from memory>
While digital zoom will reduce the quality of your image, there is a way to make good use of this feature. If you reduce the overall resolution of the image (e.g. from say 4MP to 2MP), then technically only a portion of the CDD is being used. Then, if you zoom in digitally, the camera will use the remaining unused CDD pixels (instead of using interpolation) to create the final image. This will result in less pixelation than would occur if using digital zoom at the full CCD resolution.

Can anybody confirm this? Is the explanation correct?

And, yes, I know that it's probably easier/better to just crop and enlarge a 4MP image on a PC if the camera doesn't have optical zoom. But this trick still intriges me anyway.

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Old Dec 5, 2005, 4:29 PM   #2
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This implies that, if you use digital zoom, the camera interpolates that lower-res image up to the full resolution that the sensor would normally produce. I don't think that's the case - I think the camera only saves the middle pixels, and the image comes out lower-resolution. In other words, that which you describe happens by first setting the camera to lower-resolution mode and THEN zooming, is what I think happens every time you use the digital zoom.

To ME, the advantage of using the digital zoom is this: Say that all I care about in taking a particular picture is trying to make out something in the middle of the picture. Like I'm at the beach and I see something far away in the water, and I can't quite make it out, but my 12X optical zoom plus some digital zoom might shed more detail on the mysterious and small far-away thing. In this case, using the digital zoom does not hurt that, AND produces a smaller file that wastes less space on the card. If the camera then interpolated that smaller image up to a higher resolution, this would not be the case.

However, the last time I did this was years ago (three or four cameras ago) - now I just take the picture, zoom into it on the screen to see what it is I'm trying to make out, and then delete the file (or don't, since I usually have lots of room in the card). So newer cameras (on which I have never used digital zoom) may interpolate up when you use the digital zoom, but I doubt it. Do you know for a fact that they do? Hmmm, I ought to go tryit.
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Old Dec 5, 2005, 10:15 PM   #3
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I think most cameras interpolate up to the selected resolution with digital zoom. Some don't and that is the better approach IMO. All of the cameras I have actually checked interpolate up, which was a surprise to me.

What I have problems with in your quote is that the camera uses only some of the sensors when you switch to a lower resolution. I don't think that is the case. From everything I have read the camera uses all of the sensors and just downsamples.

There are some scientific instruments that allow you to disable sensors, but they go to 1/4 resolution then 1/16 as they have to disable sensors in a proper array. I don't think going from 4 to 2Mp disables any sensors in a digital camera. Even if it did there is another leap in assuming it activates the unused sensors with digital zoom.

Unless I misunderstand what it is saying, I don't think your "trick" is valid.

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