Shutter Speed

Last time, I finished up going over aperture. Next aperture, we have shutter speed which should be a lot more simple.

Shutter speed is a measure of how long the shutter stays open.

Your digital SLR sensor like a bat; it is very sensitive to light. Since it's so sensitive to light, it 

prefers to be in the dark until the moment a photo is taken. The sensor hides behind a light-proof door called a shutter.

A shutter is made up of two separate curtains, much like curtains on a theater stage.

Every time you press the button on your camera to take a shot, one curtain opens and exposes the sensor to light, then the second curtain closes to block the light. In the case of very fast shutter speeds, the second curtain begins to close before the first is fully open.

Since the button that you press to take a photo sends a signal to the shutter curtains to open and close, it's also commonly called the "shutter release".

The amount of time that the shutter stays open is called the shutter speed.

Shutters are not lazy: they rarely stay open for very long. Most shutter speeds are measured in fractions of a second. A shutter speed of 500 actually means that the shutter is only open for 1/500th of a second.

Like aperture, there is a scale of common shutter speeds. In this case, the fraction is left out, and the shutter speed is just a single number (2000 = 1/2000th of a second).

These shutter speeds are getting slower from left to right. 1/4000th of a second is significantly faster than 1/4 of a second.

You can also set shutter speeds longer than a second. Once you cross over the second mark, shutter speeds are followed by a quote mark so that they are not confused with the fraction numbers.

A shutter speed of 2 seconds will display as 2". A shutter speed of 20 seconds is 20".

You camera might also have a shutter speed setting called "bulb". In this mode, you press the shutter release once to open the shutter and again to close it. In "bulb" mode, you can keep the shutter open for an hour if you like. It's useful in astrophotography, but other than that it isn't used much.

Shutter Priority

On a digital SLR control dial, the shutter priority setting is often labeled as "S" or "Tv".

In shutter priority mode you can manually change the shutter speed, while the camera selects a matching aperture to ensure a good exposure.

Unlike aperture which you can manipulate to your heart's content, you can't always set any shutter speed you want in shutter priority mode.

The problem here is that apertures have a limit. It's called the maximum aperture of the lens.

Without going into great detail about the aperture/shutter speed relationship (which will be covered in the future) I'll say this: getting a photo that is correctly exposed requires aperture and shutter speed to be balanced.

• As you slow down your shutter speed, letting more light into the sensor, aperture will narrow to let less light pass through the lens.
• As you increase your shutter speed, letting less light in, aperture must open wider to let more light pass through the lens.

Let's use the following example: you're using a 50mm lens with a maximum aperture of f/3.5 and you're trying to take photos on an overcast day. You set your camera to shutter priority mode, and select a shutter speed of 1/250th of a second.

The camera has no problem with this, and it picks a matching aperture of f/5.6 so that enough light hits the sensor to create a decent exposure.

Now you set the shutter speed to 1/500th of a second. Faster shutter speed = Wider aperture. The camera opens the aperture from f/5.6 to f/4 to balance the exposure.

Finally, you try to push the shutter speed up to 1/1000th of a second. The camera wants to open the aperture up to f/2.8 to get a proper exposure, but it can't. The problem: the maximum aperture of your lens (the widest it can open) is f/3.5.

Under these circumstances, your digital SLR will do one of two things:

1. It will let you take the photo, but the photo will be under-exposed (it will look too dark)
2. It won't let you take the photo, and will flash the aperture number in the viewfinder

If the second one happens to you, just slow down the shutter speed until the aperture number stops flashing, and then you'll be able to take photos again.

Shutter Speed in The Real World

Like aperture, shutter speed controls the amount of light entering the camera.

As shutter speed slows down, the camera's sensor is exposed to more light.

The amount of time the shutter must stay open is directly related to how much available light exists:

• Taking photos outside on a sunny day you can use a shutter speed of 1/1000 since there is plenty of light to get a correct exposure.
• Now you're outside on an overcast day, since with less light to work with, the shutter must stay open longer (say 1/250th of a second) to take the same photo.
• If you're taking photos indoors, the shutter may have to stay open closer to 1/60th of a second.
• At night, you'll need to use shutter speeds that are 10 seconds or longer.

Fast shutter speeds freeze motion Since the shutter is only open for a fraction of a second, you can catch a dog or a child in mid-leap, or you can show every drop of water falling into a pool. generally speaking, fast shutter speeds are used for action and sports photography, to freeze the motion of an athlete at a precise moment in time.

Slow shutter speeds blur motion. While the shutter stays open, objects that move in front of the camera lens appear blurry. This is typically used by landscape photographers to make water look silky and smooth, but can also be used to illustrate motion when taking photos of bustling city streets.

There are many times when photographers deliberately choose a shutter speed to achieve a desired effect. However, shutter speed mistakes can cause blur in a photo where there shouldn't be any.

This is basically the end of the two fundamental topics in photography.

I've talked the concept of aperture and shutter speed, and how these two camera settings affect the photos you take.

Both aperture and shutter speed are used to control the amount of light let into the camera, but one affects the depth of field while the other affects motion capture respectively.

I'm going to be mentioning these two things quite frequently later on so it's best to be familiarized with these two terms.

In the near future, I will be going into more detail between the relationship between aperture and shutter speed. I'll also be going through exposure, and why you sometimes have to override your camera's automatic settings to get a better photo. In the meantime I hope this was helpful to you.