What I meant by clean binning is theoretically 2x2 binning should be 4X the signal to noise. On KAF8300 because of something to do with the horizontal registers, see here:
http://www.ccd.com/ccd103.html
What I have read is that with the KAF8300 chip there is some issue with the horizontal register such that it does not do a proper 4X addition of the 4 pixels that make up 2x2 binning. So it loses something in the process. You can this when you use a KAF8300 camera in that 2x2 binning gives a gain but not the 4X you might expect more like 2X.
On the other hand a chip that does 2x2 binning very well like the Sony ICX694 you do see pretty much a 4X improvement and with its small pixels it emulates a 9 micron pixelled Kodak chip quite well but with increased sensitivity and lower noise. The downside is its a small chip and has a narrow FOV which is useful for some shots (galaxies).
Ray I have only experimented briefly with software 2x2 binning and noticed it also reduces resolution noticeably. So no free lunch there.
Greg.