Aperture and Shutter Speed

Aperture

The definition of aperture is a hole or an opening through which light travels. When we discus aperture settings we're talking about the size of that opening or how much light it is allowing to hit your image sensor.

Common aperture settings (sometimes called f-stops) are 1.4, 2.0, 2.8, 4.0, 5.6, 8.0, 11, 16 and 22. You can see that every other number is doubled in value. Each of these movements is a complete stop. We will cover this more when we discus exposure. But it is good to understand that from 4.0 to 5.6 is 1/2 stop. From 4.0 to 8.0 is one stop.

As you can see in the picture above, the smaller the f-stop number the larger the opening...meaning more light can come in. The higher the number, less light is allowed on to your image sensor. It can seem confusing since the smaller number is actually the larger aperture.

Aperture size is one of the major advantages in owning a DSLR. Point and shoot cameras are usually small and cheap. They almost always have very small apertures. Professionals love the ability to choose their aperture size. There are times when large is best, and there are times when small is best. The point is knowing when you need each one, and we will discuss this later.

One factor that determines the cost of a lens is its maximum aperture. A cheap lens may have a maximum aperture of 5.6. A professional lens may have a maximum aperture of 2.8 or even 1.4. You can expect to pay big bucks for a quality 2.8 lens. But for a professional it's worth it.

Shutter Speed

The shutter speed is measured in seconds, or fraction of a second. The shutter speed works in conjunction with the aperture in order to get the proper exposure.

There are times when you are shooting something in action like someone running, and you want to stop motion. For this you would need a faster shutter speed. Maybe 1/2000. There are other times where you want a slower exposure. Taking a picture of a waterfall is a good example. Taking the exposure over time will cause the water to flow while the shutter is open giving you a nice, smooth image of the water showing motion.

In this picture of a creek you can see the flowing nature of the water by setting the shutter speed to 1/8 of a second.

Most of the time you will be more concerned about aperture, and you adjust your shutter speed to match the aperture for proper exposure. But there are times where the shutter speed is most important.

The thing to remember with exposure is that the longer the shutter speed the more light your sensor gets. With a shorter the speed you will get the less light.

When we are dealing with fractions of a second, the larger the second number the faster the shutter opens and closes. For example, 1/100 is 10 times slower than 1/1000. A setting of 1/2000 is somewhat fast, and 1/60 is fairly slow.

Look at this picture at a football game shooting at 1/4000 of a second. That is an extremely fast shutter speed. Notice how he is stopped in mid air without any motion blurring? If you want to stop action and have a sharp picture of your subject then focus on using a fast shutter speed.