Cmd-Opt-Tilde (or PC Ctrl-Alt-Tilde) used to divide luminance values into high & low in CS2 & before. It made nice shaded selections, often useful for making separate curves for shadows & highlights (or low & high Zones).
In CS3, nothin' happens. Is there a new command for this, or did someone at Adobe decide we didn't need it? I even own the CS3 manual - no longer a freebie - but find no index entries under Luminance values.
Kirk