Understanding Exposure – Part 2: Shutter Speed

by Anthony Morganti

 

This is part two of our four part series, Understanding Exposure. This series of articles will explain everything a photographer needs to know about how the light gets into their camera and how their camera uses light to record the scene.

In Part 1 we discussed ISO — how it works and why you would choose a particular value of ISO.

In this, Part 2, we’ll be discussing Shutter Speed. In my opinion, Shutter Speed is the easiest of the exposure triumvirate to understand — the triumvirate being ISO, shutter speed and aperture.

In most modern DSLR’s the shutter is a curtain that moves vertically up to open and allow light that’s coming through the lens to pass to the image sensor. When the exposure is done, it closes from the bottom.

Common shutter speeds in most modern DSLR’s range from 1/4000th of a second to 30 seconds. Today’s DSLR’s also have a bulb function which means that the shutter opens and stays open until the photographer hits the shutter button again to close it. Shutter speeds of several minutes to hours can be achieved using the bulb function.

A shutter speed is considered slow at speeds below 1/30th of a second. Slow shutter speeds might be needed in very low light situations where the photographer doesn’t want to increase the ISO.

Remember from Part 1 that as ISO increases, noise i.e. grain increases. With a slow shutter speed, one can keep ISO low and the resultant image relatively noise free. Of course at slower shutter speeds you have to be concerned about camera shake so a tripod may be needed in many situations.

A photographer also my want a slow shutter speed to create some creative blur in their image.

 

Lighthouse Bell

In this shot I wanted the background to be soft to offset the hard lighthouse bell. I chose a shutter speed of 1/125th of a second that allowed the flight of the birds to be blurred which contrasted nicely with the tact sharp subject.

 

 

Conversely, when the photographer wants to freeze action, they’ll choose a fast shutter speed. Action sports such as football and hockey dictate shutter speeds upwards of 1/1000th of a second. With speeds that fast, motion is frozen with the image being crisp and blur free.

Finally, sometimes a photographer would like a shutter speed in the middle range — slower than 1/1000th of a second but faster than 1/60th of a second. A photographer will utilize these shutter speeds when they wish to convey some motion yet keep the subject relative crisp and clear.

 

In this shot I wanted to convey the motion yet keep my subject relatively sharp. Panning with a shutter speed of 1/125th of a second allowed me to achieve the look I was hoping for.

In this shot I wanted to convey the motion yet keep my subject relatively sharp. Panning with a shutter speed of 1/125th of a second allowed me to achieve the look I was hoping for.

 

Shutter Priority – Most modern DSLR’s have a setting called Shutter Priority. All this means is that the photographer will set the shutter speed and let the camera choose the aperture to achieve proper exposure. If you remember from Part 1, if the photographer has Auto ISO set, the camera will also pick the ISO needed to expose the shot.

You would use Shutter Priority when you either want to freeze the action or blur the action. As I mentioned, action sport photographers want fast shutter speeds so they’ll often have their camera in Shutter Priority mode and dial in a very fast shutter speed. They’ll than adjust the ISO to get the aperture they desire.

Of course if the photographer wants to induce some creative blur into their capture, they’ll use a slow shutter speed.

 

That is all you really need to know about shutter speed. Remember, if blur or lack of blur is most important to you, put your camera in Shutter Priority mode and pick the shutter speed that will give you the result you seek.

 

In Part 3 of Understanding Exposure we’ll be discussing Aperture — in my opinion, the most difficult of the exposure triumvirate — but still pretty easy!