Digital Zoom
Most digital cameras nowadays have a digital zoom in addition to (or, in
some cases, in stead of) an optical zoom.
The optical zoom works like any other zoom would: The glass (or in some cases,
plastic) in the lens bends the light onto the CCD, so whatever you are taking
a picture of appears closer.
A digital zoom works quite differently. Instead of doing anything with the
light that comes into the camera, a digital zoom is a software implemetation
that occurs after the image is taken into the ccd chip.
To get a digital zoom, the digital camera takes the picture as normal,
but discards the information along the edge of the camera:
+----------------------------------------+
|XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX|
|XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX|
|XXXX+------------------------------+XXXX|
|XXXX| |XXXX|
|XXXX| |XXXX|
|XXXX| |XXXX|
|XXXX| |XXXX|
|XXXX| |XXXX|
|XXXX| |XXXX|
|XXXX| |XXXX|
|XXXX+------------------------------+XXXX|
|XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX|
|XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX|
+----------------------------------------+
If the camera discards half of the pixels from the ccd (i.e only uses the
centre half of the pixels), you have a 2x digital zoom.
There are two ways digital zoom can be implemented:
1) The camera discards the outer half of the pixels, and stores the remaining
pixels to the flash memory, thus cutting storage requirements in two.
2) The camera discards the outer half of the pixels, and then interpolates
the remaining pixels so the final image has the same resolution as a non-digital
zoomed picture would have.
Advantages with digital zoom:
- You can impress your friends by saying "Look at the awesome zoom on
this camera!"
- It can help you focussing manually when doing macro photography work
Disadvantages with digital zoom:
- If your camera interpolates the image, it's a waste of storage space and
battery capacity - you could as well have resized the image in Photoshop
or any other image editing program.
- You might as well just take the picture normally, and then crop and resize
it in your favorite image editing program
The bottom line: Digital zoom - just don't bother.
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