Shutter speed is an ace feature in a camera that lets you shoot impressive shots. It can freeze time and compose a digital painting with time as well. Shutter speed is a crucial element in the exposure triangle. Let’s understand how a camera’s shutter work, what is shutter speed and how is it used in photography.
What is Shutter in Shutter Speed?
Simply put, the shutter is a piece of plate that controls the duration of exposure to light by closing and opening the sensor. The photographer can program the camera to assign this duration. However, a shutter in modern DSLRs or mirrorless cameras is not so simple. They use a focal plane shutter with two curtains.
A modern camera has two shutter plates. When we click the shutter release button, the first plate in the setup goes down exposing the camera sensor. Then, the second plate slides upwards to stop exposure after the programmed duration. This duration is called the shutter speed. Later, the shutter plates go back to their original positions.
Unlike still photographs, videos cannot use a mechanical shutter. For video recording, a camera supports an electronic shutter. The electronic shutter simulates the opening of the shutter by turning on and off the sensor. This way, the camera can store video without a mechanical shutter movement.
Shutter Speed in Photography
Now that you have understood how a shutter works, let’s move on to shutter speed. Shutter speed is the duration for which the shutter remains open for sensor exposure. Modern cameras offer shutter speeds from 1/8000s to 30s. Continuous shooting (burst) speed is also dependent on how fast the shutter can perform. Cameras such as Sony a9 II boasts up to 20 fps continuous shooting speed with an electronic shutter (10 fps with mechanical shutter).
Shutter speed also controls the amount of light entering the camera. Slower shutter speeds allow more light into the sensor. However, a blur can be induced in the image due to moving objects while using slow shutter speeds. A photographer can produce interesting images with slower or faster shutter speeds.
Shutter speed is classified into fast shutter, slow shutter, and long shutter:
Fast Shutter Speed
Cameras are sometimes referred to as time machines. Its ability to freeze time and capture it allowed this comparison. In photography, shutters speeds faster than 1/1000th of a second falls into the category of fast shutter speed. It assists in capturing fast-moving action scenes. Animal photography, bird photography, sports photography, and anything that involves fast movement require fast shutter speed. Adversely, this will in effect reduce the light entering the camera. Tweaking the aperture and ISO without compromising in the depth of field or noise is crucial.
Slow Shutter Speed
Shutter speed slower than or up to 1/100 s falls into the category of slow shutter speed. We can capture stills of slow-moving objects that we see daily within this shutter speed range. Portrait photographers and street photographers can use this speed range to get better results.
Long Shutter Speed
Anything longer than 1s is called long shutter speed. Modern cameras support up to 30 s shutter speed. Make sure to use a tripod at this speed if you don’t have steady hands. You can capture long traffic trails, or take a picture of Milky way, or make a light painting with this speed range. Photographers all over the world are trying out new things every day, maybe you can do something unique with this too. I made this picture when I was a student. It is not aesthetic, but that is how a long exposure shot is made. I set the shutter speed at 6s, and then went in front of the camera and played with my torch after turning it on.
Rolling Shutter & Global Shutter
Now that we have looked into shutter and shutter speed, let’s move on to something deeper. There are two methods to read an image falling into the sensor. Global shutter sensors read each pixel data simultaneously. They were most common in CCD sensors. The advanced DSLRs or mirrorless cameras feature a CMOS sensor. And CMOS has a readout mechanism different from the global shutter.
Unlike global shutter, rolling shutter sensors read out pixel data row by row from top to down. The circuitry is simple and inexpensive for a rolling shutter. However, rolling shutter induces distortions when there is relative motion between camera and subject. You might have already noticed this effect when shooting anything that moves fast. This effect skews the image in the opposite direction of the camera’s motion.
Rolling shutter is not intrinsic to the CMOS sensor. Even though, all present CMOS sensor cameras have this issue. The higher-end cinematic video camera manufacturers like Blackmagic, ARRI, etc, have managed developed circuitry that efficiently removes the effect of rolling shutter. But this is not practical in still photography cameras as it will drastically increase the camera price. Therefore, it is best that you understand your camera. Learn what you can shoot, and what you cannot. Choosing a slower shutter speed when there is any very fast action can induce blur and compensate the skew. However, it is not possible in every situation.
Shutter Speed and the Exposure Triangle
Controlling shutter speed allows you to control the incoming light. In addition, the aperture also controls the amount of light entering the camera. But here is the catch, aperture compromises on the depth of field whereas shutter speed compromise on the risk of motion blur. The photographer has to analyze what he/she is shooting and decide the shutter parameters. ISO can be of real help at these moments to boost you with an exposure enhancement. However, increasing the ISO will also induce noise.
Prolonged exposure may also induce a disturbing shade into the image due to light pollution. This is visible during long exposure shots of a city, or interference of the light while taking sky photos. It is crucial for a photographer to understand his/her camera to get better results. You can control the shutter speed either in shutter priority mode or manual mode.
Shutter Priority Mode
Shutter priority mode allows the user to control the shutter speed. However, this mode does not allow a user to change the ISO or aperture. The camera uses metering to set ISO and aperture values in shutter priority mode. Even though the system tries to use minimum ISO, chances of getting a noisy image are higher in low light conditions.
Switching to manual focus allows the user to control the three options flexibly. The crisp control over these options allows the user to set the right settings that suit the shooting environment. A photographer should master the skill to analyze a shooting environment and judge the exposure parameters.