Dark picture..not bright picture
The whole point of a webcam is to be able to see the person you are speaking with, and let them see you. When the image broadcasted by your camera is too dark, the person on the viewing end won't see anything but shadows and dark shapes. Learn how to brighten your webcam image so the people you chat with can see you.
Place lamps behind and to the side of the webcam. This casts a light on your face, but the lamps will not wash out the image because they are behind the camera. Turn off lamps that are behind you. You have trouble seeing things when you are looking in the direction of the sun or a light bulb. Your webcam has the same problems. Don't make it stare at a bright light. Open up a white screen on your computer to brighten your face. The white screen will create the brightest possible light from you computer screen and help lighten your webcam image. This option is best when lamps are not available. Open up an empty tab in your Internet browser, or a blank Notepad document, and expand it to the full of your screen. Adjust your webcam settings. The settings available to you will depend on your webcam, but many of them offer a "Brightness" setting that you can increase to lighten your webcam. Open the program that came with your webcam, then look for a "Settings" or "Options" menu. Increase the "Brightness" setting until it has lightened your webcam enough.