Shutter Speed defines how long the camera’s “window” is open to capture the available light and therefore the image. The shorter the Shutter Speed, the more light is required (or the more a camera’s sensitivity to light matters) to get a proper exposure. Alternatively, a longer Shutter Speed has more time to gather light and can be over-exposed if there is too much light.
Examples of a shot requiring a fast shutter speed would be of a hummingbird’s wings mid-flight or a Formula 1 race car at top speed. In these cases, a very short Shutter Speed (into the 1000th of a second or more) is necessary to freeze the action.
An example of a longer Shutter Speed might be anywhere from a half-second to a multi-minute or longer exposure maybe in an evening venue or photographing the evening sky filled with stars.
So how can you figure out what SS is required for a given shot? You can just put your camera on Auto and then check to see what settings the camera picked, you can decide on a desired SS and select Shutter Priority (S for Nikon Tv for Canon) and let the camera pick the Aperture to get the proper exposure or you can go to my new favorite setting Manual and set SS, Aperture and ISO for yourself!
So what if you want a faster SS than you can achieve with your widest Aperture? You can bump up your ISO to make the sensor more sensitive to light. This is a good place to experiment. Depending on how new/good your camera is you may be able to bump ISO up above 1000 to get that faster SS you need for your shot.
On the other end of the spectrum, you may find yourself wanting to do a longer exposure to achieve a silky effect on flowing water or to give a surreal look to moving clouds during the day. In this case you may need to apply a neutral density filter that blocks some of the light. ND filters come in varying densities that can add multiple “stops” worth of light blocking to allow you to take longer exposure shots during the day.
I’ll write a future post on photographing star-trails, light trails and other long-exposure trickery. Next up: ISOby Rich