PART 3 Visualizing the Story Auto-iris systems work by measuring the brightness of the lens image falling on the sensor chip. Most auto-iris systems concentrate on the center area of the frame. Some are designed to avoid being over-influenced by the top of the frame, where bright skies, for example, could falsely reduce the exposure. The best systems judge exposure by sampling all parts of the image. MANUAL IRIS ADJUSTMENT Turning the iris/diaphragm ring on the lens barrel (see Figure 7.41) allows the camera operator to decide exactly how the image should be exposed. The overall picture brightness can be adjusted and compensation can be made for features in the scene that would fool the auto-iris system. REMOTE IRIS CONTROL When a camera is connected to a CCU (see Figure 7.21), usually in a multicamera situation, its lens aperture is usually set to suit prevailing light conditions by the video operator, who is also known as a shader. During a production, the lens aperture of each camera can be remotely controlled, either with coarse adjustment (several stops) or more usually with a fine control (e.g., half a stop) to vary exposure subtly for the best image quality. Camera Lens Filters Filters of various kinds can be attached to the front of the lens, located in the camera's internal filter wheel or inserted into a matte box on the front of the