Shutter speed determines how much light reaches the camera’s imaging sensor (chip).
It is the amount of time during which the digital sensor inside the camera is exposed to light. The shutter speed is most often measured by fractions of a second (e.g., 1/800 sec.).
However, longer shutter speeds can expose the sensor to light for longer periods of time, such as minutes, hours and occasionally days. Shutter speed is incredibly important in terms of the creative control of images and different speeds can create very different images. A faster shutter speed can captures images frozen in time, while slower speeds can create a blur.
However, it is important to consider the light levels present.
With very bright lights you can use a faster shutter speed because enough light is going into the sensor; yet in low-light conditions you must use a slower shutter speed.
Similarly, in bright conditions a slower shutter speed will expose the image to too much light, which will make it washed out and very bright. While this may seem confusing at first, it is simply a matter of understanding that shutter speed determines the effect in the image – e.g., the showing of motion and blur, or the freezing of moments and capturing a snapshot in time.
It is closely linked to light levels and must be adjusted accordingly.