Last post, “Lens Aperture Explained – Exposure Triangle Pt.1″ was the first part in this 3-part series on the Exposure Triangle. If you haven’t read it yet, you can go there now.
Today we’ll be going over Shutter Speed, what it is and how to use it to your advantage.
If you’ve ever taken a picture, you know that you must press the shutter button in order to capture the image. But what exactly is the shutter?
According to Wikipedia:
- “In photography, a shutter is a device that allows light to pass for a determined period of time, for the purpose of exposing photographic film or a light-sensitive electronic sensor to light to capture a permanent image of a scene.”
The camera’s shutter is always closed until you press the shutter release. This prevents light from entering the camera and hitting the sensor until you’re ready to capture an image.
In TTL (through-the-lens) cameras, there is also a mirror that moves out of the way when the shutter button is pressed. With the high-end digital cameras there is an option to have the mirror move out of the way on the first press of the shutter. Then a second press of the shutter button opens the shutter to take the picture. When the shutter button is released both the shutter and the mirror move back into place. This is know as “mirror lock-up”, and you can find more information about that in your camera’s manual.
So now that we have an understanding of what the shutter is, let’s look at how it affects your exposure.
As mentioned above, an open shutter allows light to hit the sensor, creating an image. Therefore, the longer the shutter is left open, the more light enters the camera. The less time the shutter is open, the less light enters. Pretty straight forward so far.
If you’re taking pictures outdoors on a nice sunny day, you want a faster shutter speed. This will allow less light in giving you the correct exposure.
On the other hand, if you’re taking pictures indoors, or outdoors with less light, you need a slower shutter speed to allow more light to enter the camera.
How is shutter speed measured?
Shutter speeds are represented by fractions of a second; 1/30, 1/60, 1/80, 1/100, etc. This is usually shown by just the second number. For example, “500″ means 1/500th of a second. Shutter speeds of 1 second or longer are represented with a ” after the number. For example, 30″ represents a 30-second exposure.
There’s one more symbol you might see relating to shutter speed, “B”. This is the “Bulb” setting, which allows you to keep the shutter open as long as the shutter button is pressed.
How do you adjust the shutter speed?
On digital cameras you can adjust the shutter speed by using the cameras menu system and dials. Each camera make and model will have its own system of selecting these modes. If you’re not sure how to do it with your camera, refer to the camera manual.
So now we know that the shutter speed has a direct impact on exposure.
Next, let’s take a look at some examples of how shutter speed affects the image exposure.
Under Exposed
Over Exposed
Correct Exposure
*Note: The white balance of these images is wrong. But that’s not what we’re worried about now!
You can see that the shutter speed is very important in achieving the correct exposure!
Next, we will be covering ISO and how it affects the Exposure Triangle. Stay tuned!
by Nate
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