In my last post, I explained that with a little understanding of a few key basics, you can take your camera off automatic mode and take full creative control – it will change the way you take photographs forever!
The camera has three key ways for you to control the light that enters the camera, namely; Aperture, Shutter Speed and ISO. All three of these work together to help create a well exposed photograph. I previously set out how using the camera’s aperture control effects the outcome of your pictures and you can read that blog post here http://antonyz.com/aperture/
In this post, I am going to explain why you would choose to control the shutter speed. In case you are not sure, the shutter is the ‘doorway’ inside the camera that shields the camera’s sensor from light. When you press the shutter button you are telling the camera to open the shutter and let in light for a set amount of time. This light is recorded on the camera’s sensor as your final image. You can control this timeframe depending on your specific camera but this often ranges from between an 8000th of a second to 30 seconds and beyond.
So on a bright sunny day, or in a scene where there is a lot of artificial light, you would not want your shutter to remain open too long as all that light would flood into the camera and leave you with a white or overexposed image. Therefore you would want to choose a faster shutter speed in these circumstances. Conversely, using a slower shutter speed will let in more light to the camera when it is darker and there is less ambient light and this will help the camera make a more balanced and correct exposure. Accordingly at dusk or night time you would choose a slower shutter speed.
However, as seen with aperture in the last post, you can also use the shutter speed to an additional creative effect when taking photographs.
If the subject is moving quickly then you can use a faster shutter speed to record this fast movement as sharply as possible and in effect freeze the action.
A slower shutter speed will allow the camera to record a scene for a longer amount of time giving parts of the scene time to move and this movement be recorded in the final photograph. This technique can be useful to capture the essence of movement in an image and adds an additional dynamic to your photographs.
Another common example of using a slow shutter to record this kind of movement is where cars drive through a dark scene with their lights on and you want to record the light trails as streaks of light through the image. Here are a few examples of this (the shutter speed times in these images range from between 10-30 seconds):
A further common example of using a slow shutter speed is to blur the movement of water, such as the ocean tides and waterfalls. Again the following images had shutter speed times of over 15 seconds or more.
The final common usage of using a slower shutter speed if to help the camera take in more light in a dark scene and record a well balanced image. This is commonly used in night photography where there is not much ambient light available to light up the scene.
It is important to remember that when you are using a slower shutter speed that you will need to support your camera with a tripod or something else stable to avoid shaking the camera and blurring the image. A usual rule of thumb is that you should use a tripod if the shutter speed is shorter than the focal length you are using, so for example using a 100mm lens, if your shutter speed is less than 1/100 of a second.