The Split Toning tool in the Develop pallet of Adobe Lightroom 1.0 allows you to set separate Hue and Saturation values for Highlights and Shadows in a digital image. I will use a closeup of the Quoddy West Lighthouse (the furthest most eastern point in the US), to illustrate the effect Split Toning can have on an image with pronounced shadows and highlights.

More subtle effects can of course also be generated with this set of tools, but I am going to go overboard on these examples to illustrate the results possible more easily.

The default image with no values in the settings.

A value of 111 (a strong green) in the highlights and a value of 0 (a strong red) in the Shadows, with Saturation for both being set at maximum to better illustrate the effect. The Balance has been set at -11 to give a little more prominence to the red Hue values.

A value of 0 (a strong red) in the highlights and a value of 111 (a strong green) in the Shadows, with Saturation for both again being set at maximum to better illustrate the effect. This time the Balance has been tipped towards the green Hue values.

The Highlights and Shadows have been given the same Hue value in the last image, but they have been assigned different Saturation values. Just a little warmth has been added to the highlights to keep them relatively clean and believable, but the Shadows area has been given a much larger amount of Saturation to make them appear as warm as the highlights.