Exposure is a balancing act of three elements, shutter speed, ISO, and f stop. Quite often one of these elements will be chosen, at the expense of another.
Shutter speed is one of three elements that are used to create a successful image.
Slow shutter speed will blur the action, i.e. below 1/30 second
Paddys River Falls in flood was shot at 1/15 second. To achieve a slow shutter speed in high contrast sunlight, sometimes a filter is needed to decrease the amount of light hitting the sensor. In this case I used a polarising filter, but a Neutral Density filter can also be used. When using a shutter speed lower than 1/60 second, it is advisable to use a tripod.
Fast shutter speed will freeze fast moving objects, i.e. usually above 1/500 second
If you need a fast shutter speed, to freeze the action as with this pelican in flight. I needed to set my shutter speed to 1/1000 second to achieve this fast action I needed to let more light into the sensor, so I needed to increase my ISO up to 1250 and then choose an f stop to give correct exposure
The piglets racing toward their bucket of mash was shot at 1/320 second
These young footballers were shot at 1/1600 second
This young man playing football was shot at 1/800, but it was still not fast enough to freeze the ball or his boot.
Water skiing on Talbingo Dam, a shutter speed of 1/1250 second is needed to freeze the water spray. To being able to use this shutter speed, I needed to increase the ISO to 500 while maintaining an f stop of 6.3 which blurred the background