Interface Images Toned Images by Keith Ratcliffe  © 2006

Creating veils of white in waterfalls (This one is at Aberuchil near Comrie) by long exposure is a common technique
 and one that works well with toning. By careful adjustment of the curves you can hold the pure white and feed in the tone in a controlled manner.
 It works very differently to the 'colorise' tool in the Saturation menu.