On 2/1/08, John Francis <[EMAIL PROTECTED]> wrote: > On Fri, Feb 01, 2008 at 02:40:12PM +0800, Sandy Harris wrote: > > 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? > > That's not how it works. When you add four pixels, each with > a random noise component, you only improve the signal-to-noise > ratio by a factor of two, not by a factor of four. So theory > says the best you could hope for is one stop of improvement. >
Which is what P&S's often do for their high ISO's. But their sensor sites are so small that they really have to do that. -- M. Adam Maas http://www.mawz.ca Explorations of the City Around Us. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
