Hossam el-Hamalawy's Library tagged Silhouette →  View Popular, Search in Google

Most modern digital cameras have automatic metering which are pretty good at sensing how to expose a photograph so that everything is well lit. The problem with this is that most cameras are so smart that they will light up your subject instead of underexposing it to get a silhouette so you need to trick it. Most cameras work out the exposure levels in auto mode when you push your shutter half way down (at the same time that they focus). So point your camera at the brightest part of your picture and then press the shutter halfway down (don’t let go). Then move your camera back to frame your shot with the subject where you want it and then finish taking the shot. With most digital cameras this will result in a silhouetted subject. In effect what you’re doing is tricking your camera into thinking that the bright part of the image is the mid tone of it so that anything darker than it will be exposed as a nice dark shadow.

Some digital cameras also have ’spot’ or ‘centered’ metering modes that you can switch on which helps with the above technique as they will set the metering on the central spot of your frame rather than multiple spots. This means you can accurately tell your camera exactly which bit of the bright background you want it to set the exposure on.