On Wednesday, September 20, 2006 9:52 PM Terry Bishop wrote:
Also use the least
digital zoom as possible.
That's the advice I always hear, but is it strictly true? Most people seem
to be of the opinion that if you're going to digitally enlarge a photo, then
it's better to do it with the more powerful software available on your
computer.
I have a theory that this may not be true if your camera can only save
photos as jpg's. These are compressed and some information has been lost
from the image that was captured. So enlarging the compressed image later
may not give as good a result as allowing the camera to do the same
operation on the raw image before compressing it, if it does indeed do it
that way.
My camera (Canon Powershot A40) appears to do the digital zoom operation
using the raw image before saving it as a jpg. I've proven it to myself by
taking a photo of a newspaper at a distance where the writing was barely
legible on the final image. Taking another photo from twice as far, but
with 2x digital zoom, resulted in an image that was noticeably easier to
read. I've never actually tested it on a real subject, bird or otherwise,
because they tend to move while you're moving back for the digital zoom
shot, and the differences can be too subtle to allow you to decide which
image is better anyway.
I guess it depends on your camera. If it can save raw images, then it seems
it would be better to enlarge them later. If it only saves jpg's then it
depends whether its digital zoom enlarges them before or after compressing.
I suspect they probably all do it before, but you'd want to do the same test
I did before trusting it.
It could also depend on the quality of the algorithm used for the digital
zoom. A camera with a slow processor may use a quicker, low quality
algorithm, negating the advantages of enlarging before compressing. But
then again, such a camera may also have a low quality compression algorithm,
making the digital zoom advantageous. There are no standards for jpg
compression: what some cameras do with what they call "super fine" may lose
a lot more information than another camera's ""fine" mode.
Summary: Using digital zoom *can* be better than enlarging later with
software, but you'll have to test it with your camera to be sure.
It goes without saying that setting the camera to the highest resolution and
best quality compression can only help too.
Peter Shute
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