How are "smaller" than 16MPx pictures obtained (such as 2MPx video)?

Started Oct 8, 2011 | Discussions thread
mauthbaux
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Re: How are "smaller" than 16MPx pictures obtained (such as 2MPx video)?
In reply to dvcinlv, Oct 16, 2011

As a related question, would shooting at a lower pixel count effectively increase the light sensitivity of the camera? If the smaller images come from a simple downscale of the sensors frame buffer, then I'd assume we'd see less noise (averaging of data), but no real increase in low light performance. However, if you could treat the adjacent like photosites as if they were the same (adding rather than averaging), you'd effectively be gather more light data per pixel, and have better low-light performance. e.g. could I still get good images shooting at low ISO in the dark if I was only taking 0.3MPx images?

Also, how does this relate to black and white images? Per pixel data point, there's 4 times as much light being gathered. Are the photosites simply averaged? Any particular reason you can't take black and white images at 4 times the size of a color image using the same sensor?

Disclaimer: This is all just naive armchair hypothesizing. I'm not nearly as familiar with this as I probably ought to be.

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