How can you control exposure?
As I mentioned, obtaining correct exposure is a setting combination of ISO, aperture and shutter speed. For example, your camera’s light meter may have measured a need for an aperture of F8 at a shutter speed of 1/30 sec at ISO 200. If you press the shutter release button now, your camera will close up the iris to an aperture of F8 and open the shutter for only 1/30 sec. to obtain a correctly exposed picture. The amount of light that squeezes through that opening for that amount of time goes to expose the image sensor.
Digital Camera Bootcamp for beginners is an 8 week program