A Short Course Book
Using Your Digital Camera
A Guide To Great Photographs

How To Photograph Motion Sharply

 
 
Click to explore how camera-subject distance affects shutter speeds.
 
 
Click to explore how shutter speed affects sharpness.
 
 
On this speeding train, the part closest to the camera looks the most blurred while the farthest part looks sharper. Since all parts of the train are moving at the same speed, this shows how distance affects blur.
The sharpness of different parts of an image helps direct the viewer who tends to look first at the most sharply focused part of the picture. In addition, sharpness itself can be part of the message of the photograph. The immobility of a frozen figure can be made more apparent by blurring people moving in other parts of the image.

Blur in a photo is caused when all or part of a subject focused onto the image sensor moves when the shutter is open. To show a moving subject sharply, the shutter needs to open and close before the image focused onto the sensor moves a significant amount. In other words, you need to use a fast shutter speed. But just how fast is fast enough? The answer depends on several factors which makes it hard to always predict how motion will be portrayed in the final photograph. To be safe, use different settings while taking more than one shot. Try shooting from a different angle or perhaps wait for a pause in the action. You are much more likely to get a good shot if you have several to choose from. Just be aware that sharpness and blur are hard to evaluate on the camera's monitor.

Speed of Subject

The faster a subject is moving, the faster the shutter speed you need for a sharp image. However, it's not the speed of the subject in the real world that determines blur. It's how far the subject moves on the image sensor while the exposure is being made. This depends not just on the subject's actual speed, but also on the direction of its movement, its distance from the camera, and the focal length of the lens.

The shutter speed froze the central dancer but was slow enough to blur the others. This makes the central dancer the most important person in the photograph.
 
To capture fast action, point the camera toward where the action will occur and press the shutter button halfway down to set focus and exposure. Hold the button down until the action happens and you'll be able to get a shot off a lot faster.

Direction of Movement

When the shutter is open, a subject moving parallel to the image sensor will cross more of the pixels on the sensor and be more blurred than a subject moving directly toward or away from the camera. This is why you can use a slower shutter speed to sharply photograph a subject moving toward or away from you, and not the same subject moving from one side of the scene to the other at the same speed.

Distance to Subject and Focal Length of Lens

If a subject is close to the camera, even slight movement is enough to cause blur. A subject—or part of one—far from the camera can move a considerable distance before its image on the image sensor moves very much. The focal length of the lens affects the apparent distance to the subject. Increasing the focal length of your lens—for example, zooming in on a subject—has the same effect as moving closer to your subject. The more you are zoomed in on it, the less a subject has to move in order to have its image move far enough on the image sensor to appear blurred. To visualize the effects of distance on blur, look out the side window of a speeding car (but not when you're driving). The objects in the foreground seem to fly by while those on the horizon don't seem to move at all.

The shutter speed needed to control the sharpness of a moving object is determined by the subject's speed, direction of movement, and distance.
 
HOW TO: INCREASING SHARPNESS OF MOVING OBJECTS

. Photograph fast moving subjects heading toward or away from you.
. Move farther back from the subject or use a shorter focal length lens.
. Switch to shutter-priority mode and select a fast shutter speed such as 1/500.
. Increase the ISO although this adds some noise to the image.


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