What is Shutter?
1. The shutter is a device that is positioned in front of the camera sensor to prevent light coming in through the lens from reaching the sensor.
2. The shutter can be opened for a specific period to expose the sensor to light and capture the image.
3. The shutter speed determines the amount of time the sensor is exposed to light and consequently has an impact on the exposure.
How does the Shutter work?
1. Most modern DSLR cameras use a Focal Plane shutter.
2. It’s called a focal plane shutter because it sits right in front of the focal plane i.e. sensor or film of the camera.
3. It consists of 2 parts namely the first curtain and the second curtain.
4. In its initial position when an image is not being taken the first curtain is positioned in front of the sensor and the second curtain is positioned above the first curtain.
5. When the shutter button is pressed to take the image the first curtain drops from the front of the sensor thus exposing the sensor to light for the amount of time specified by the shutter speed and then the second curtain drops to cover the sensor and complete the exposure.
6. Once the exposure is completed the two curtains are reset to their original position.
In the initial position the first curtain covers the sensor
When the shutter button is pressed the first curtain drops exposing the sensor to light.
After the interval set in the shutter speed, the second curtain drops completing the exposure.
1. The shutter speeds can vary from 30 seconds tupto 1/8000th of a second in DSLR cameras.
2. What is interesting is that the physical speed of the curtains do not change.
3. It remains the same irrespective of the shutter speed that is set.
4. So how does the shutter reduce the exposure time? In case of higher shutter speeds the two curtains move down simultaneously keeping the gap between them in such a way that all portions of the sensor are exposed to light only for the duration of the shutter speed set.
In case of fast shutter speeds the two curtains move simultaneously.
Impact of Shutter Speed on exposure and motion capture
1. The shutter speed has an impact on the exposure time and also the way motion is captured.
2. The slower the shutter speed the greater the exposure of the sensor to light. The exposure decreases with increase in shutter speed.
3. The shutter speed also determines the way the camera captures motion. If the shutter speed is faster than the movement of the subject, then the subject will be frozen and if the shutter speed is slower than the motion of the subject, then the moving subject will be blurred. This type of blur is referred to as Motion Blur.
