Does Photoshop (CS3)have the capability to give you numerical pixel counts of individual shades of color in a photograph? We are running an experiment to keep track of different algae colors over time in an artificial stream bed.
I'm not sure if this feature is available in CS3 (i'm running CS4 extended). If it is it would only be in the extended version.
You can use the histogram in the 'Analysis' workspace (under the Window > Workspace > Analysis menu selection) to select specific levels and get a pixel count as well as other information. You'll want to do more research into this feature to find out exactly how you want to use it.