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Shooting Mode Dial: Shutter-Priority AE

The (Shooting) Mode Dial is the round dial sitting on the top of your camera, usually on the top right side (viewing from the rear). It has different settings marked on it, such as Auto, PASM, and perhaps C, SCN, etc., depending on your camera. Most beginners leave it on the Auto setting (in the picture above, it’s the iA setting), which tells the camera to go ahead and make all the exposure decisions for you.

Enthusiast photographers may opt to choose one of the other settings, usually one of the PASM settings, giving them more control over the exposure. In this article, we look at the Shutter-Priority AE shooting mode, what it is, why you would want to use it and a couple of practical ways how you can make use of it for more creative photography.

WHAT
The Shutter-Priority AE mode is labeled “S” or “Tv” on the Shooting Mode Dial. It is a semi-automatic mode where you manually choose the shutter speed you want to use and the camera chooses the appropriate aperture for a correct exposure.

On the camera to the left, the Mode Dial has PASM settings, where the “S” setting indicates the Shutter-Priority mode.

PASM: P = Program AE, A = Aperture-Priority AE, S = Shutter-Priority AE and M = Full Manual.

On the camera to the right, there is no Mode Dial, but instead a proper Shutter Speed Dial that lists the shutter speeds available, in this case 1 sec., 1/2 sec., 1/4 sec., etc. all the way to a fast 1/4000 sec. “B” (Bulb) allows you to keep the shutter open for as long as you keep the shutter release button depressed (though with digital cameras, there is always a limit); “T” (Time) is similar to “B” except that you pre-select the long shutter speed, don’t have to keep your finger on the shutter release button, the camera will count down and close the shutter for you. Some people like to think of the “A” here as indicating Aperture-Priority mode, though the “A” here really stands for Automatic, i.e. you are telling the camera to choose the shutter speed for you automatically (which is the case for both Aperture-Priority mode and Program mode). On this camera, Shutter-Priority mode is inferred by you simply selecting a shutter speed and leaving the aperture ring on the lens on “A” (i.e. telling the camera to select an aperture Automatically).

Shutter speeds are usually marked in 1 stop increments, with each stop either approximately doubling or halving the time, depending on which way you are going.

For example, in the camera above right, the Shutter Speed Dial is engraved starting at 1 second, then half of that is 1/2 sec., half of that is 1/4 sec., to 1/8 sec., 1/15 sec. 1/30 sec., 1/60 sec., 1/125 sec., 1/250 sec., 1/500 sec., 1/1000 sec., 1/2000 sec. and, finally, 1/4000 sec. (The 1/180 sec. anomaly is there only because that’s the flash sync speed on this particular camera.)

Using a fast shutter speed means leaving the shutter open for only a very brief amount of time (a fraction of a second: the smaller the fraction, the faster the shutter speed). Therefore, we say that the shutter speed increases as we progress from 1 sec. to 1/4000 sec.

Using a slow (or long) shutter speed means leaving the shutter open for a long amount of time. Therefore, we say that the shutter speed decreases as we progress from 1/4000 sec. to 1 sec.

If all other exposure settings remain unchanged, increasing the shutter speed by 1 stop (e.g. from 1 sec. to 1/2 sec., or from 1/60 sec. to 1/125 sec.) will result in approximately halving the amount of light coming in; decreasing the shutter speed by 1 stop (e.g. from 1/2 sec. to 1 sec., or from 1/125 sec. to 1/60 sec.) will result in approximately doubling the amount of light coming in.

WHY
Most beginner photographers don’t think the shutter speed the camera chooses in Auto mode may affect the picture they take, but in fact it does. Most cameras in Auto mode will try to choose a combination of shutter speed and aperture that will result in a correctly exposed picture.

What the camera does not know is whether you are taking a picture of a kid running with a soccer ball, jumping in the air on his skateboard or skipping rope. If the camera chooses a shutter speed that is too slow, the result is a blurred photo since your kid may have moved during the time the shutter stayed opened to record the scene.

You want to choose a shutter speed that is appropriate for the scene.

Since the shutter speed is the time (measured in full seconds or fractions of a second) that you allow the shutter to remain open, Shutter-Priority mode allows you to manually choose a fast shutter speed (such as 1/250 sec.), a slow one (such as 1/2 sec.) or even an extra slow/long shutter speed (such as 60 sec.).

The primary reason you’ll find yourself using the Shutter-Priority mode is to manually select a shutter speed fast enough to freeze action or a slow shutter speed to blur motion.

HOW
Here are a couple of practical examples on how you can use Shutter-Priority mode to your advantage.

To freeze action (sports, active children), use a fast shutter speed: the faster the action, the faster the shutter speed you want to choose, anything from 1/125 sec. to 1/2000 sec. (or whatever is the fastest shutter speed available on your camera).

In the picture above, if a slow shutter speed were used, the skateborder would be blurred.

To blur motion (or to obtain the water cloud effect), select a slow shutter speed. Fireworks require from 3 seconds and longer. Night photography requires a shutter speed in the double digits.

Blurred motion obtained by using a slow shutter speed can also effectively depict motion, as in the picture below:

In the picture below of a waterfall, a long shutter speed allows the photographer to obtain a smooth, cloud-like effect.

In the picture below, a long shutter speed is required to capture the city lights. Since the shutter remains open for a long time, the tail lights of cars get recorded as a trail of colored lights.

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