Trading resolution for high ISO

[Sandy Harris]

There are lots of photos that do not need to have high resolution.
The new high-definition TVs are just under 2 megapixels, as is a
4" by 5" print at 300 dpi. PC screens range from about .5 to
about three Mp. For most web display anything over one Mp
or so is wasted.

So given, say, a K20D with its 14 Mp, can we somehow
combine sets of four dots to get a 3.5 Mp image with
better performance in "available darkness"? Or would
this also push noise up, perhaps to awfuI levels?

How much would you gain? Four times the pixel area,
so in theory two stops, but would that happen in
practice?

-- 
Sandy Harris,
Nanjing, China