Solarisation and the Sabattier effect
You can use the tone curve to replicate the results of some of the artistic processes used by photographic darkroom printers. This particular effect, sometimes called the Sabattier effect and sometimes called solarisation, would be achieved by briefly exposing the partially developed print to bright white light, usually sunlight. The areas that are already developed will be unaffected, but the areas still developing will undergo a tone reversal. While difficult, time consuming and expensive to produce in the darkroom, the same effect is relatively simple using the tone curve.
The effect works just as well in monochrome as it does in colour. Simply anchor the upper part of the curve to its default position, then drag the lower half of the curve into a “U” shape. The effect of this is to leave the highlight areas unchanged, but to reverse the tone of the shadow areas, just as with a traditional Sabattier effect. You can add contrast by dragging the lowest part of the curve right to the bottom, to produce some areas of black.
Photoshop Elements 8 has a pre-set on the Curves dialogue called Solarisation, but it produces a different although not unattractive effect, reversing the mid-tones to produce something part-way between solarisation and posterisation. The intensity of the effect can be adjusted using the sliders.
Hopefully this tutorial has given you a few ideas, and shown you some of the things you can do with the tone curve. I've included the sample shot used in this tutorial as a download on the first page, so you can experiment for yourself, and find out what works for you.