No they are not. Yes you can leave your shutter open for a long time and gather a bunch of light to your sensor to achieve a well-lit picture. However, you have to have your camera set up on a stand where it's not being affected by your motion or the motion of a vehicle or the wind or whatever. It has to hold perfectly still or the shot gets screwed up. Flash enables you to light the scene in an instant without having to set up mounting hardware and getting people to stay out of the line of sight of the camera while it's taking its long ass picture.