Understanding shutter speed – and how it can help your photography

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.

The graph below shows the relationship between shutter speed and aperture.

Moving along the bottom of the graph from left to right the graph shows that as the shutter speed gets less the aperture gets bigger to compensate.

At all points along the bottom the exposure will still contain the full 1,000 units needed for a correctly exposed scene, the change is the proportion that is made up by the aperture and how much is made up by the shutter speed.

Take the mid-point; 500 units of light will be let in through the aperture, and 500 will be let in by a specific shutter speed.

Move to two thirds of the way along the graph and the aperture part of the exposure is now worth more. At this point the aperture lets in 650 units of light with the other 350 units coming from a faster shutter speed.

image showing the relationship between shutter speed and aperture in order to get a properly balanced exposure in photography

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.

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: