Is digital zoom a worthless gimmick?

Started Jul 25, 2013 | Discussions thread
Futax
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Re: Is digital zoom a worthless gimmick?
In reply to bssfujifan, Jul 26, 2013

I haven't posted on this forum for ages, but I thought I'd join in because it's an interesting subject.

Firstly, as has been pointed out, there is no advantage or disadvantage in using digital zoom (or digital TC) as regards shake or shutter speed.  They'll all suffer the same amount of blur as cropping.  A real TC won't affect the shake issue either (assuming it hasn't affected aperture value or light transmission), you just need to trade off the resolution/noise advantage versus image degradation due to optical limitations.

Paul Till makes a good point that digital zoom can help getting the correct focus.  However, it can also work against getting the right composition, if the image on the screen or in the viewfinder is bouncing around a bit.  In these situations cropping allows you to get the best composition at your leisure.

The other issue regarding digital zoom is that the camera uses a cropped image and upsamples this to the same resolution as a normal image.  I think this is where the term "interpolation" comes in: the extra pixels are added by interpolating between neighbouring pixels.  However, I think this is all a bit counter-productive.  You're not going to print or display the image at full resolution anyway; the image has to be downsampled before it can be printed or displayed at any sensible size, so all the interpolation is doing is adding approximation to the original image.  (Mind you, in practice, I rather doubt the image will be substantially degraded by this, because I've not seen much difference when I've looked at test images on this and other forums.)

In conclusion, I don't think there's much to choose between digital zoom or cropping, really.  But if you're using digital zoom and finding it difficult to keep the camera steady enough to get the right composition, don't be afraid to use the cropping route...

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