Taken in RAW and in Manual mode with a Nikon D300s and a Nikon 24-85 lens (macro setting), set at a focal length of 85mm. Other settings include an ISO value of 400, a shutter speed of 1/250th sec and F4. Shot was tripod mounted.
A pyrex dish was filled with water and placed on top of some coloured card. Then drops of olive oil were added. A spectrum gradient layer was added with the blending mode set to hue in CS5.