by Julieanne Kost
In Photoshop CS4 we changed the keyboard shortcuts for viewing channels:
“The shortcut to display an individual channel in Photoshop CS3 was previously assigned to Cmd (Mac) / Ctrl (Win) +1, 2, 3, etc. Cmd+1 would show Red, Cmd+2 would show Green, etc. Those shortcuts, in Photoshop CS4 were shifted two places to the right. Therefore Cmd+3 shows Red, Cmd=4 shows Green, etc. (Cmd + 2 shows the composite).”
For those who still prefer the legacy shortcuts for switching among channels, (i.e. you want them set back to PSCS3), select Edit > Keyboard Shortcuts and use the check box to enable “Use Legacy Channel Shortcuts”.