It's difficult to be specific without seeing the prints, and knowing what you are aiming at. There are many photo-manipulation programs that can probably do what you want, including equalising histograms (which ensure you have a full range from black to white), increasing contrast (which reduces the amount of grey, increasing the amount of black and white), and altering the gamma level (which makes the mid- greys lighter or darker).(posted 9172 days ago)