This is a video taken directly from an excellent PDF found at http://www.thelightsrightstudio.com/tutorials-pdf.htm where a couple of techniques using a saturation mask are discussed: pulling back saturation in an image where only one channel was over-exposed (thus clipped or “blown out”) and a second technique to add saturation through the saturation mask to an image already possessing strongly saturated regions that would be over-done if the hue-saturation adjustment layer were applied overall. This technique obtains its saturation mask from an HSB channel using a filter found on the first of the “Extras” disks that comes with the Adobe CS installation disks (and a similarly working plugin can be found online as well, that works on flattened duplicates only).