Gamma. This whole monitor calibration thing is very confusing. You essentially have to get the calibration right on your scanner, your monitor and your printer so that colors don't shift and so you don't lose anything.
Adobe Photoshop includes an Adobe Gamma calibrator for this purpose. You can also buy a device that is like a little electric eye to do direct calibration called the ColorVision.
Finally, you can eyeball things and use a tool called Powerstrip to remember all the calibrations for you.
