Shutter speed? If you own a point and shoot compact digital camera you may never have come across the term “shutter speed” before.
This is because these cameras do pretty much everything for you in terms of exposure so that your photos are well exposed every time.
They tend to do a good job these days too. Years ago cameras didn’t come with “auto” settings.
The photographer had to set the shutter speed and the aperture manually for every photo.
I remember using light meters and making fine adjustments to my camera just so that I could get a well exposed shot.
It was a real pain!
The one thing it did teach me though was how exposure works.
So what is shutter speed? Should you be concerned about it? How can you use it to take better photos? This page will answer your questions!
What is shutter speed?
For any given scene there will be an optimum exposure. The exposure is a measure of how much light hits the sensor of your digital camera (in the old days it was how much light hit the film).
Think of it in these terms;
- A properly exposed photo might need 1,000 “units” of light to hit the sensor.
- If you let in too much light (maybe, 2,000 units) your photo will be overexposed – it will appear bleached out.
- If you don’t let in enough light (maybe, 500 units) then the photo will be underexposed – it will appear too dark.
Your camera can do one of two things to ensure 1,000 units hit the sensor;
The first thing is to open the shutter for a set period of time - this is called the shutter speed. When the shutter opens, the sensor on your digital camera is exposed to light. When it closes no more light can enter.
Example: If opening the shutter for half a second lets in 500 units of light, doubling that to one second will let in the 1,000 units you need for a well exposed photo.
The second way your camera can allow those 1,000 units in is to make the hole at the front of the camera wider (this hole is the aperture).
Example: The shutter speed can stay at half a second, but make the hole at the front of the camera twice as large and 1,000 units of light can enter in that same half a second.
Click here for more on how the aperture works, or click here for more on understanding exposure. (links open in new windows)
Great! But what’s the “shutter”?
I’ve mentioned the camera’s “shutter” a few times, without actually explaining what it is! It helps to think of this in terms of film cameras.
When we used film and not digital sensors to record photos things were a little different. Not much different, just a little!
Film is sensitive to light, so it had to be kept in the dark until you exposed it to take a photo. Once the photo was taken it had to go back into the dark to avoid overexposing it.
So how was this done? Film came in light proof cassettes. You loaded this cassette into your camera. The inside of the camera was also light proof. So once the film was in, it was safely in the dark.
At the front of the camera there was the lens that focussed light onto the film. But stopping the light reaching the film was the shutter blade. This was a thin sheet of metal (or dark cloth in really old cameras), blocking the light.
When you pressed the shutter . . . the shutter blade moved out of the way . . . the film was exposed . . . then the shutter blade moved back to re-cover the film. Phew!
The amount of time the film was exposed is called the shutter speed. Because film is soooo sensitive to light, the amount of time it was exposed was brief – just a fraction of a second. And this is how it’s measured – in fractions of seconds.
A slow shutter speed is considered to be less than 1/30th of a second. Any slower than this (1/15th of a second or less), and it is too difficult to keep the camera still - photos look blurred. If you can keep the camera still enough (by using a tripod, perhaps), then the subject could end up blurred.
A fast shutter speed is considered to be more than 1/500th of a second. Because the film is exposed for such a brief period, movement is frozen. These are the speeds sports photographers use to freeze athletes in motion.
Film? And you thought this was a digital photography site! Yep, it is. All you have to think about when it comes to digital photography is that the film has now been replaced by an electronic image sensor.
So instead of the film being exposed, in digital photography the image sensor is exposed. The effect is exactly the same as if you were using film.
Fast shutter speed, slow shutter speed – what use is knowing that?
Once you know that a slow shutter speed will result in blur, and a fast shutter speed will freeze action, you can put it to creative use.
For example, if you are taking photos of children on school sports day, you might want to freeze the moment when they cross the finish line. You now know that you will need a fast shutter speed to do this!
If you are taking photos where you want to show movement, you could use a slow shutter speed.
Flowing water is a common one - because of the slow shutter speed the water will appear blurred (because it moved when the shutter was open), but anything that didn’t move would be in focus.
Have a look at the photo to the left here. It demonstrates this use of slow shutter speed.
I took this photo in Malaysia. It’s one of the seven waterfalls that make up the Kanching waterfalls.
I deliberately used a slow shutter speed to show the movement in the water, but, because nothing else in the photo moved, the rest of the photo is in focus.
Further reading . . .
Now you have an understanding of what we mean by fast shutter speed and slow shutter speed, you might find the following pages worth a read:
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