Black-and-white photography has made a well-deserved recovery from its near death when color began to dominate publications in the 1980's and 1990's. Black-and-white now has become a "fine-art" medium reserved for "special" photography. Now I don't believe that is true at all. Black-and-white is a wonderful way of photographing that can invigorate any photographer's work and even make their color imagery better.
A challenge I consistently see among photographers wanting to work with black-and-white is to consider it simply photography without color. When one believes that, then you think only in terms of finding a good color image and removing its color to get a good black-and-white shot. That will not give you the best in black-and-white. That will lead you astray to a very wrong place for good black-and-white work.
Black-and-white is its own medium and needs to be thought of that way. I like to think of translating not simply converting color to black-and-white. Anyone can learn to convert one language to another, for example, but that won't mean they will communicate very well with it. To translate from one language to another is an art if it is to be done well.
The same thing occurs with how color is changed to shades of gray for a black-and-white image. You can just "convert" the image by removing the color, but that won't get you a truly effective translation of the color image into black-and-white. None of the photos here are simple conversions to black-and-white that just removed color. How you change colors into specific shades of gray, for example, should the red be a dark or light gray, and how will that affect a dark or light green, is important.
Contrast is a key element in defining any image, but in black-and-white, you are quite limited by having none of the color contrasts that are possible. A big problem many photographers have when translating color to black-and-white is that they are so impressed by the great color contrasts of a photo that they remember these contrasts even after the image has been converted to color. They still see details in the image because of that color memory even though no one else will because they only see the shades of gray of the black-and-white photo and those grays are too similar to be easily discerned.
Here is a shot of California poppies in bloom and it is translated in two different ways. You can see how much tonalities change based on how colors are rendered in shades of gray.
There are three basic contrasts that can help you think about black-and-white when shooting for the medium and two of them affect what you look for in order to best translate color to black-and-white:
1. Tonal or brightness contrast. This is the big one and it can dominate everything else. Anytime you have your subject brighter or darker than its surroundings, you get a tonal contrast. The stronger the difference in brightness, the stronger the contrast. Such contrasts can come from light and shadow as well as different inherent brightness of the subject and its surroundings. If you recognize how important this is, you will watch for inadvertant tonal contrasts, such as an unwanted bright sky at an upper corner of the image. Tonal contrasts do not have to just be between subject and surroundings -- you can also use them to create a rich pattern of light and dark to define a composition. Tonal contrast is one of the most important contrasts to look for as you translate a color image into black-and-white. Every black-and-white conversion software I have used includes the ability to change how colors are translated into different shades of gray to affect this contrast. My favorite is Nik Software Silver Efex Pro, but I find that a lot of photographers are distracted by the special effects that are in the previews and forget to use the very important color filter settings on the right -- that is one of the first things I do after choosing a basic look on the left.
2. Texture or pattern contrast. Anytime you have a big difference in the appearance of one texture or pattern next to another, you create contrast. This can make for very rich looking black-and-white images. Putting two textures next to each other, even if different, won't do much unless the textures are quite different so there is a real contrast between them. This is a secondary contrast and can be overwhelmed by a strong tonal contrast, which can especially be a problem if there is a bright sky creating a tonal contrast that overpowers everything else. Textures and patterns are definitely affected by how colors are translated into shades of gray, too.
3. Sharpness contrast. This is the classic black-and-white photojournalist contrast because often he/she did not have any other way of separating the subject from the background. This happens any time you have a very sharp subject surrounded by out-of-focus background and/or foreground. The new popularity of fast prime lenses, such as a 50mm f/2 or f/1.4, has occurred in part because of the amazing sharpness contrast that happens when a subject is shot at f/2 or f/1.4. Don't be afraid to shoot any lens wide-open for its dramatic sharpness contrast potential. This cannot be affected by how colors are translated to black-and-white, though there is software that can create sharpness contrast. It can also be overpowered by inappropriate brightness contrast.
My BetterPhoto.com class, Mastering Black-and-White, is a course that covers both shooting and working with black-and-white in the computer. Every lesson includes multiple video lessons to help you see what is possible in black-and-white.
All of the desert images are from Death Valley. The poppies are from Montana de Oro State Park in Los Osos, California. These images are not simple translations, either. They use the full range of traditional black-and-white darkroom controls to affect things like the brightness of edges, local brightness and contrast and more.