This is a bowl of oranges. Shot with my digital camera and processed in black and white. All the oranges were the same color. So why do they look so different here?
Because HOW you process an image in black and white can make a great deal of difference. A digital color photograph is made up of three channels of color information. Red, Green and Blue (RGB). These three colors combine to give us all the colors we can see in color prints from our digital photographs.
When looking at the luminencnce or brightness values of each of these channels you see some pretty different things. Looking at the red channel of this photo show very light oranges, looking at the blue channel shows very dark oranges. In the photograph below I simply chose to show different channels or mixture of channels on different oranges, given the variety of tones you see below.
This is very important in black and white photography. Do you want a light sky or do you want a dark sky? Do you want lighter skin tones or darker skin tones. Black and White give you a lot of creative latitude so be sure to explore the possibilities next time you convert to black and white.