A few shortcuts changed in Photoshop CS4 when we simplified the way that adjustments worked by taking them out of modal dialog boxes and putting them into panels. Because a modal dialog box is it’s own little world, it can use shortcuts that are already used in Photoshop “proper”. However, when we put adjustments like Curves, Levels, etc. in the Adjustment panel, we no longer have that isolated context. As a result:
• The shortcut to display an individual channel in a Photoshop file 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, have now shifted two places to the right. Therefore Cmd+3 shows Red, Cmd=4 shows Green, etc. (Cmd + 2 shows the composite).
• Previously, when targeting a channel in a modal dialog box (such as Curves, Levels, etc.), you used Cmd (Mac) / Ctrl (Win) +1, 2, 3, etc. Cmd+1 would target Red, Cmd+2 would show Green, etc. Just like the shortcuts for displaying channels, those shortcuts have all shifted two places to the right. When using the panel-based adjustments, the shortcuts have changed to Opt (Mac) / Alt (Win) +1, 2, 3, etc.
• The Hue/Saturation and Selective Color commands are slightly different as they don’t map to just RGB/CMYK, but the same general rules apply: Opt+2 selects the Master channel, and Opt+3, 4, etc. select the subsequent items in the list.
If you prefer to return to the shortcuts found in Photoshop CS3, you can download a ZIP file containing a plug-in (Mac)/registry entries (Windows) that remap the channel keys to CS3 behaviors courtesy of Adobe’s John Nack.
Having read all this, you might reasonably say, “Fine, but Photoshop offers a keyboard shortcut editor, so let me switch things back if I’d like.” That’s not possible, for a couple of reasons. One, the change from modal dialogs to non-modal panel simply means that some commands would now conflict (e.g. hitting Cmd-1 can’t both display a channel & target a channel), so just restoring the old behavior isn’t an option. Two, the shortcut editor frankly isn’t robust enough to handle certain special-purpose keys (numbers, tilde, etc.), and we didn’t have time to enhance it for CS4.
We have, however, created a solution: you can download a file containing a plug-in (Mac)/registry entries (Windows) that remap the channel keys (http://blogs.adobe.com/jnack/files/Use_Old_Shortcuts.zip). That is, you give up using Cmd-~ to switch among open documents, and you lose Cmd-1 for zooming to 100%, but tilde will go back to selecting the composite channel and 1, 2, 3, etc. will go back to selecting/targeting the first, second, third, etc. channels. The Mac plug-in just needs to be dropped into your Photoshop plug-ins directory, and on Windows you can enable/disable the behavior by double-clicking the reg entries.
Thanks to John Nack for this detailed shortcut information! (blogs.adobe.com/jnack)