Colormancer

Colormancer is a Photoshop plugin that lets you tweak contrast, brightness, and saturation to bring out depth and dimensionality in your images. Colormancer will literally change and enhance the appearance of the photos you edit.
Colormancer is designed to avoid the color shifts of existing tools. When adjusting brightness and contrast, Colormancer keeps hue and saturation constant by maintaining a constant ratio between the red, green, and blue values of each pixel.
Unlike using a Curves adjustment on RGB values, Colormancer avoids the decreased saturation in highlights. It also avoids the hue and saturation shifts in the other tonal ranges.
Here are some key features of "Colormancer":
ï¿­ All internal calculations performed with 32-bit floating point precision
ï¿­ Supports 8-bit, 16-bit, and 32-bit RGB and Grayscale modes
ï¿­ Smart filter enabled
Requirements:
ï¿­ Adobe PhotoShop CS3
ï¿­ Photoshop Elements 2 or higher
Limitations:
ï¿­ Watermark on the output