Shutter speed in digital photography

By: Akash Deep

Digital cameras have made life so easy for budding photographers as cameras come with pre determined settings for shooting in different conditions. But if you want to capture images realistic images, it is important to understand the various settings available in the camera to take you out of the auto mode.

There are three main elements which can be manually adjusted to change the exposure of shots taken. These three areas are shutter speed, aperture and ISO. We have already looked at ISO adjustments and now it is time to get to grips with shutter speed.

Definition of Shutter Speed

In simple terms, the shutter speed is a measure of the time for which the shutter of the camera remains open. Higher times will result in more light on the image sensors which can result in various effects on the images.

When compared to the analog photography, in digital photography shutter speed is the time for which the image sensor captures the photograph which is similar to the exposure time of the film in analog photography.

We will now break down shutter speed into easy to understand pieces which will help you in understanding this element more clearly.

Unit of measurement of shutter speed

The unit of measurement of shutter speed is fractions of seconds. The lower the shutter speed, the faster it is. In other words, 1/1000 is faster than a 1/500. In literal terms, this defines the length of time for which the shutter of the camera was open for the light to be captured by the image sensor.

Shutter speed settings in digital cameras

Most of the digital cameras today come with shutter speed settings which approximately double with next setting. Therefore, commonly the shutter speed options on your digital camera will be something like 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500.

It is important to remember that with each setting in the increasing order, you are cutting down on the light received on the image sensor by almost half. It is important to understand this basic concept. This setting works similar to the aperture setting as each next setting (moving the setting from f16 to f11) approximately lets in twice the amount of light than the previous setting.

Therefore, when you increase the shutter speed by one setting and decrease the aperture by one setting, it results in almost same exposure levels. This will be discussed in much detail in later posts.

How to choose shutter speed

Choosing a shutter speed to capture an image depends on the scene you are trying to capture. Faster or slower shutter speed will depend on the movement of any object in the scene and the effect you want to have.

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If there is a moving object in the scene and you would like to freeze the moment, then you should choose faster shutter speeds as it will capture light for a very short amount of time and there will not be any motion blur (this result in giving a sense of movement to the object in the image).

If you want to blur the movement of the object in the scene, you should choose a slower shutter speed as it will allow you to capture the light for a longer period of time which will result in a motion blur. The exact shutter speed depends on the speed of the object and how much the motion needs to be blurred.

Most of the time, still images do not need to capture a motion but there are certain images which just come into their own with motion. There are many digital camera owners who have felt the need to shoot with a lower shutter speed.

Take the example of a waterfall or a racing car. In case, you want to capture the flow of water or you want to capture the feeling of speed in the racing car, it will be better to use slower shutter speed to capture the full effect. Slower shutter speed is also useful in capturing a star scape which shows the movement of stars over a long period of time. Faster shutter speed in the above cases will result in very different lifeless images. The slower shutter speed will make the image come alive.

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There are some cameras available in the market that has the option of extremely slow shutter speeds. The speed is so slow that it is measured in seconds and not fraction of seconds. So, one can expose the sensor for something like 10 seconds, 20 seconds or 40 seconds and so on. These cameras are made for special situations like when one has to shoot in very low light. These are also useful for capturing a large movement in a single shot.

There are also cameras known as Bulb cameras. These bulb cameras have the option to keep the shutter open as long as the button is kept pressed.

What is camera shake?

When the camera keeps moving on with its shutter open, it results in a blurred image and this is known as camera shake. Most of the digital cameras today come with in built image stabilization feature which cancels the camera shake to a large extent. You can also use a tripod in case you are capturing images with slower shutter speeds (this is essential for shutter speeds slower than 1/60). Click here to read more on getting sharp images.

Relationship between shutter speed and focal length

Focal length of the camera also affects the shutter speed to be chosen for a particular scene. Camera shake is accentuated by longer focal lengths. To stabilize the image, you will need to use faster shutter speed with longer focal length cameras.

If you do not have image stabilization available, then always choose a shutter speed which has a denominator bigger than the focal length. So, if the focal length of the lens is 200 mm, the shutter speed should be close to 1/250 and 1/125 shutter speed is okay for focal length of 100 mm.

Although, we have covered the topic of shutter speed in great detail above, it is important to remember that shutter speed does not work in isolation. The other two elements, aperture and ISO are also important. Changing shutter speed can be compensated with changes in these two other elements.

To give you an example, increasing the shutter speed from 1/250 to 1/125 will result in halving the amount of light into the camera which can be compensated by a fast ISO rating (moving from ISO 100 to ISO 400).

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