Saturation is for increasing or decreasing the intensity of the colors in the image. Contrast increases or decreases the difference between light and dark areas in the image. Out of curiosity, why are you shooting in JPEG instead of RAW? JPEG flattens the image (layers wise) and really limits your ability to change paramerters like saturation and contrast. I would suggest you switch to RAW instead of JPEG and use a program like Photoshop (or Photoshop Elements) or Lightroom to "tweak" your images. It is better to leave the image in the camera alone and make any improvements in post processing. In the camera, any and all changes are forever, you cannot undo them if you overdo them (which I suspect you are doing with your sharpening). Oversharpening in JPEG potentially leads to jpeg artifacts which can really adversely affect the image.