Your shutter speed controls how long your shutter stays open for an exposure. If you have a lot of light on a subject, the shutter closes fast, if you have low light, the shutter speed is slow. Pretty basic. The faster the shutter speed, the sharper your images. Have you ever taken a picture of your kid wiggling and gotten a very blurry arm or leg, or whole body? That is a slower shutter speed where the object was moving faster than the shutter could open and close.
Take for example this super fast kung foo baby- notice the blur in the last frame? A slightly faster shutter speed would have made that clear, but in this case the motion was emphasized by using a slightly slower shutters speed.
Shutter Speed Exercise
Try setting your camera to shutter speed priority. Have a kid or a spouse or a crazy neighbor pose for you and wiggle around. Start at a slower shutter speed, maybe 1/25. Take the picture and repeat, increasing your shutter speed. Do you notice that the picture is slightly blurred, becoming increasingly sharp the faster your shutter speed? If you can see the information on the photo, notice how the camera has compensated for the different shutter speeds by adjusting the aperture.
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