hi burn and doge lighten and darken, and in their specific case, they lighten or darkend the assigned density (highlight or shadow). an easy overall way to lighten or darken an image is in the curves menu codec3

Hi well, a 'mask' only uses black and white info. A layer can be in color. The best way to do this...umm create a mask or alpha channel...is to simply look at the channel pallet, turn off RGB, then click off the r,g,b channels until you find the one you think works best. Duplicate that channel, then in the channel fly-out show the 'mask' with red (the default color). That extra channel can be exported into apps like After Effects and used as a transparency layer, well it works in PShop, too codec3