Black Backdrop
A black backdrop is very effective for low-key lighting. In this technique a photographer meters on the brightest point of the subject. In metering for the brightest spot, the rest of image appears dark and the shadows are completely black. This technique is used in portrait, still life, fashion and fine art photography.
White Backdrop
The opposite to low-key photography is high-key photography. Using a white background gives images a very clean, pure look when the images are properly exposed, the tendency is for these images to be underexposed as the white background tricks the camera's light meter to read the scene as brighter than it really is. To achieve high-key images, photographers meter on the darkest area of the picture. This creates an image that appears almost as though it was overexposed. As with low-key photography this technique can be used in a number of different studio shooting scenarios, such as portrait, still life or glamour photography.
Exposure Compensation -- Black Background
Cameras read reflective light. With a black background there will be little or no light reflected back to the camera. This will cause the camera to read the scene as darker than it really is and will cause the picture to be overexposed. When shooting with a black background you should underexpose the picture by one to two stops. Especially if a lot of the background appears in the picture.
Exposure Compensation -- White Background
White backgrounds cause the camera to read a scene as brighter than it really is. This will cause the camera to underexpose as the meter is reading light reflected from the white background which can result in a dull, greyish look. When shooting against a white background, overexpose the picture by one to two stops to compensate and even out the brightness. If you are using lights to illuminate the backdrop you may need to set the exposure compensation even higher.