In this tutorial, we’ll answer the following questions:
- What is a shutter?
- What is a shutter speed?
- How do I change the shutter speeds?
- What are those funny numbers?
- What effect does changing shutter speed have?
What is a shutter?
A shutter is a mechanism in your camera that allows light to pass through it while it is open, and prevents light from passing though when it is closed. There are many different types of shutters on different cameras, but the most common type, found in all SLR cameras is a focal plane shutter.
A focal plane shutter is simply a thin metal or cloth gate, which is parallel to the film inside your camera.
The shutter is normally closed, preventing light from reaching the film, but opens for a predefined period of time when you press the ‘shutter release’ button, which is the button you use to take a photograph.
What is a shutter speed?
When you take a photo, the shutter opens for a predefined length of time. This time is referred to as the shutter speed. This is one of the two major methods of controlling how much light reaches your film (the other being the aperture). Shutter speeds are measured in seconds, or fractions of a second. Typical shutter speeds range from between 1 second to 1/4000 of a second, although using a shutter speed of several hours is not unheard of.
Each time you double or half the shutter speed, you are doubling or halving the amount of light you are letting through.
How do I change the shutter speeds?
This depends on what camera you have. On a manual exposure camera there is normally either a dial on the top right of the camera or a ring around the lens.
On an automatic camera you need to set your camera into the correct exposure mode (basically whichever one allows you to choose the shutter speed rather than getting the camera to do it for you) and then typically there is a control dial. This does vary a lot between different cameras so if in doubt, ask someone to show you.
What are those funny numbers?
Shutter speeds are fortunately very easy to understand. When changing your shutter speed you will see a series of numbers such as 500, 250, 125, 60, 30, 15, 10, 4, 2. Often a few numbers such as (1, 2, 4) will follow this, but they will either be a different colour (typically red) or followed by a . symbol.
The first set of numbers represents fractions of a second. So if you select 250, you will actually be using a shutter speed of 1/250 second, if you select 4 you will be using a shutter speed of a quarter of a second.
The second sets of numbers are whole seconds. So 1 is 1 second, 2 is 2 seconds and so on.
What effect does changing shutter speed have?
The main effect of shutter speed is to control the amount of light reaching the film. However there is a second, and very important effect – that of movement!
If you use a shutter speed of 1 second, then you are not taking a photo of an instant of time, but of a 1 second long period of time. Most things will move over the duration of 1 second.
Once something has been exposed to the film, its image will remain on the film. So if something is moving across the frame of your photo during the 1 second of your exposure, it will blur, as every part of the photo that the object has moved though, will record an image of it. However as it will not be at any one place for the entire second, it will appear fainter than if the object had remained still for the entire second.
So, you might want to use a fast shutter speed (1/500 – 1/1000) for movement such as martial arts or wildlife photos whilst some interesting effects can be achieved by using a slow shutter speed (1-2 sec) at night of a street with cars driving passed, most everyday photos however speeds of 1/45-1/250 are normally used
The other aspect of movement is about you, your movement, and that of your camera. Continuing the example of a 1 second long exposure, unless you are using a tripod you are not going to be able to hold the camera perfectly still for 1 second.
When you also consider that the shutter is moving in the camera, and there is a big mirror, which has moved very fast, it becomes clear that your camera is going to shake slightly whenever you take a photo. This shake will cause your images to appear blurry.
There is a rule of thumb that tells you the slowest shutter speed you can use, while holding the camera in your hands, and not expect to see the effects of this camera shake. The shutter speed should be the reciprocal of the focal length of your lens, or faster.
The reason for this is that longer focal length lenses magnify the image, and so magnify the effect of camera shake. Also longer lenses tend to be physically larger, and so harder to hold still.