My Photo Shop window didn't have the "Effects" button you, Wikipedia, and my Snow Leopard manual mention, so I had to do some exploring. That, and the help I just got by calling Apple, led me to a very satisfactory answer. Here's the story. First, in order to get the "Effects" button, I clicked on HELP in the menu bar while using Photo Shop and typed "Effects" in the HELP search bar. That opened the proper Photo Booth on my desktop to replace the one that didn't have an "Effects" button.
I selected the photo I wanted to edit from my Photo Shop file and dragged it to my desktop. It made a file there, which I opened. Next, I clicked on "PREVIEW" at the left of the menu bar. I then clicked on HELP and typed the word ADJUST in the HELP search bar. That opened a window with slider controls for Exposure, Contrast, Saturation, Temperature, Tint, Sepia, and Sharpness. Just what I wanted. I remember the section for teenagers, but I never used it. This window is what grownups need.