Back to basics Part 2- What is shutter speed?

Last week we looked at the exposure triangle and how aperture affects exposure. This week, we will focus on shutter speed and ISO. These two elements make up the remainder of the exposure triangle.

Shutter speed, just like aperture, also controls the amount of lighting hitting the sensor of the camera. Inside the camera, right in front of the sensor, you have two shutters. When you press the trigger to take a photo, the first shutter that covers the sensor drops down and exposes the sensor to light. The second shutter then drops down to close the sensor from light. The amount of time the sensor is exposed to light is known as the shutter speed. On your camera, this is denoted by a fraction of a second, e.g. 1/250^th of a second.

The longer the shutter stays open, the more light reaches the sensor and you have a brighter image or a brighter exposure. This is a slow shutter speed.

The faster the shutters close, the less the light reaches the sensor and the darker the image will be. This is a fast shutter speed.

In food photography, the shutter speed will control the movement in your images. There are two types of movement you can have in food photography, unintentional and intentional.

Unintentional movement is caused by the camera shaking, something you don’t want happening in food photography. This could be from your hands shaking whilst holding the camera or the camera shaking when you press the trigger button. If your shutter speed is too slow, your image will become blurred because of this.

Intentional movement is when your food moves on set- think along the lines of pouring of liquid, drizzling of dressing and stirring or mixing a drink. You can also have hands moving on your set such as a hand mixing batter for example. If you want to freeze the movement and have the movement perfectly in focus, you need a fast shutter speed. If you want to blur the movement (blurred movement implies that something is moving but the actual movement is blurred and the focus is on another part of the image), you want a slow shutter speed.

So what is considered a fast shutter speed and what is considered a slow shutter speed in food photography? Well, this is very much dependent on the lens you are using. Each lens has a cut off point below which movement starts to blur.

You can actually calculate a lens’s cut off point or minimum shutter very simply.  As a rule of thumb, you should use a minimum shutter speed of 1/focal length. So for a 200mm lens, use a shutter speed of at least 1/200^th. For a 50mm lens, use a shutter speed of at least 1/200^th.

Knowing the minimum shutter speed of each lens helps you for two main reasons:

1. You now know what’s the minimum shutter speed you can safely hand hold the camera with that lens and NOT get unintentional motion blur
2. You now know what shutter speed to use to freeze movement and blur movement. Anything above the minimum shutter speed will freeze movement. Anything below the minimum shutter speed will blur movement and the slower you go with shutter speed, the more blur you will get.

For example, if I am using a 50mm lens, the minimum shutter speed will be 1/50^th. Anything above 1/50^th will freeze movement. Below 1/50^th and the movement will look blurred. The slower I go, the more the movement will blur.

To conclude, here are the main points covered:

• Shutter speed is the length of time the camera’s shutters are open, exposing the sensor to light.
• Slow shutter speed means the sensor is exposed to light for longer giving you a brighter image. Large fraction e.g. 1/30^th of a second
• Fast shutter speed means the sensor is exposed to light for a shorter time giving you a darker image. Small fraction e.g. 1/500^th of a second
• Movement is controlled by shutter speed and you have unintentional and intentional movement
• Minimum shutter speed depends on the lens you are using
• To freeze movement, use a faster shutter speed
• To blur movement, use a slow shutter speed.