Date   : Fri, 06 Jan 2006 12:44:24 +0000
From   : Jules Richardson <julesrichardsonuk@...>
Subject: Re: Advice on digital photographs

Ian Wolstenholme wrote:
> I have also found (particularly to get clear pictures of bits of motherboard)
that
> doing a long shot on the highest resolution and then cutting the picture
down to
> the part you want will work.  I usually put the topless Beeb, for instance,
on the
> dining room table, stand on one of the chairs or even stand on the table,
and then
> take a picture like that.  With all these megapixels you can quite often
still get a
> decent sized image of the bit you want doing it this way.

MP values quoted by camera manufacturers are actually marketing speak though - 
what they actually quote is the raw number of receptors on the camera's CCD, 
where each receptor is only able to resolve one primary colour. (you can see 
this if if your camera has raw mode, which just produces an unprocessed and 
non-lossy dump of the image hitting the CCD)

The actual number of full colour pixels that the camera is able to resolve 
ends up between a third and a quarter of the quoted megapixel value. Cameras 
do a lot of internal processing to turn the CCD image into a JPG file (which 
can get in the way in some situations)

Upshot of that is that you're much better off using macro mode and filling the 
camera's CCD, then downscaling in software later - the resulting image should 
be less grainy (it does depend on intended usage of course - for a 640x480 web 
image say, it probably doesn't matter! :)

cheers

Jules