Shutter Speed And Motion

To make a sharp picture of a subject in motion, you need a fast enough shutter speed to freeze the motion. How fast is "fast enough"? This depends on several things.

Look at this sequence of photos of a motorcycle going about 30 mph taken at 1/15, 1730, 1/60, 1/125, 1/250, 1/500, and 1/1000 of a second.

The shorter the exposure, the sharper the image. At 1/1000 we have certainly "frozen" the image. But is that the effect we w^ant? Maybe, and maybe not.

Let's say that our desire is to express the daredevil speed of the motorcyclist. Does the frozen image express this? Does it express motion? We think not. The slightly blurred image at 1/125 may better express the feeling of motion even though sharpness of detail is lost. To express motion as a pure concept, rather than a specific person in motion, the totally blurred image at 1/15 or 1/30 of a second may be the right shot.

The right shutter speed is the speed at which you get the effect you want - the shutter speed that helpsyou express your theme.

1/60

1/125

1/250

Frame Gu2365

1/1000

4. Focal length of the lens. The longer the lens, the larger the image of the subject on the film. The larger the image, the faster it will move across the frame.

50mm

105mm

3. Distance from the moving object. The closer the camera is to the moving object, the larger the image of the object will be on the film. The larger the image on the film, the faster it will move across the frame. Look at the next two photos. They were taken with the same lens at the same shutter speed - 1/60 second. The only difference is that the first was shot from 20 feet away and the second, from 40 feet away. To compare the blurring of the image, we have enlarged the motorcycle in both to the same size.

As you can see, the motorcycle is much more blurred when shot from 20 feet away than 40 feet away. From this you know that the farther you are from a moving object, the less the blurring caused by the motion. The closer you are to a moving object, the more the blurring caused by the motion.

4. Focal length of the lens. The longer the lens, the larger the image of the subject on the film. The larger the image, the faster it will move across the frame.

Using a longer lens is equivalent to moving in closer to the moving object. As you already know, if you move in closer, the moving object will be more blurred in the image. Look at the next two pictures to see how the same happens if you use a longer lens. Both these pictures were taken with the same shutter speed — 1/60 — from the same distance. The only difference is that one was taken with a 50mm lens and the other with a 105mm lens. To compare the blurring of the image, we have enlarged the motorcycle in both to the same size. Clearly the image is more blurred with the 105mm lens.

50mm

105mm

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