Electronic Shutter

As discussed earlier, all camera systems work on the principle of conversion of light into electric signal. In general terms, more is the illumination, better is the picture. But, too much of illumination also is bad for the image as it tends to shine/bloom in access of illumination. For a evenly illuminated image, we need controlled light. The amount of light that has to be taken in is controlled by a special apparatus called as shutter. Shutters are incorporated in the design of the equipment. Shutters are mechanical or electronic in nature. Mechanism of Mechanical Shutter can be best explained on comparing it with the Iris of our eyes. When we come out of a dark surrounding into sunlight, our eyes contract instinctively. Alongwith this, the Iris, that is the door of sensing aperture, also decreases its open area to restrict the amount of light that enters the eye-ball. This is to avoid the blooming and getting a coherent image that falls in the line of vision. Similarly, the camera also has an aperture through which the light enters and encounters the chip. This aperture’s opening/closing is controlled by the mechanical shutter. This mechanical shutter has moving parts. Obviously, this is prone to damage. Also, the response to light changes is very slow.

Modern day cameras use shutters that control the incoming amount of light electronically. This is achieved by activating the pixels on chip for a limited amount of time. This time of activation is dependant upon the intensity of incoming light. By keeping the activation of pixels only for a limited amount of time in one cycle, we can control the incoming light so as to get a picture with perfect brightness. This control is done automatically. Thus, when we say that a camera is working in auto mode, we mean that shutter control is automatic. Cameras can be used in manual mode also, but this is done only when the light source is in auto mode. It is important to note that when the light source is functioning is automatic mode, the camera has to be in manual mode and when the light source is in manual mode, the camera has to be in auto mode. When the light source is in manual mode and camera is in auto mode, there is no need for any specific arrangement. The light source emits light as programmed manually and the camera, in turn, senses the intensity of reflected light and adjusts automatically using its electronic shutter control. On the other hand, when light source is in auto mode and the camera is in manual mode, it is the light source that has to adjust the emission of light so as to get a quality image. The camera does not adjust for light intensity. In order to facilitate the control on the intensity of emitted light, the light source has to be given a feedback from the camera. This feedback ‘tells’ the light source about the intensity requirements. The light source, that is in auto mode, then adjusts its output so as to get a quality image.