[TriLUG] OT: multiple resolutions on digital cameras

[Joseph Mack NA3T via TriLUG]

My P&S Canon SD750 has a 7.1Mpixel sensor and is capable of outputting
pictures of

3072*2304
2592*1944
2048*1536
1600*1200
  640* 480

Assuming the active part of the sensor is 3072*2304, I would expect that the
camera can only lower the resolution by binning pixels, say two at a time.
so you would have

3072*2304
1536*1152

but not

3072*2304
2592*1944

The resolutions above don't have a simple relation of division by small 
integers. I assume that a picture taken at the different resolutions would cover 
the same area being photographed, so presumably the change in resolution is not 
by dropping large areas around the side of the picture.

I expect you can sample at greater than the Nyquist rate without loss of 
information. The sensor could capture 3072*2304 and output 640x480, but that 
only accounts for the lowest resolution in the list above.

Got any idea how cameras change their resolution?

Google wasn't helpful. All they tell me is which button to press to change 
resolution.

Thanks
Joe

-- 
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
jmack (at) austintek (dot) com - azimuthal equidistant
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