Adjustments to aperture, ISO and speed all have different advantages and disadvantages, so understanding what happens with each element of the triad is important in understanding which one you want to adjust when setting your exposure. In this post, I am focusing on shutter speed.
Shutter speed is another way of controlling the light coming into your camera. The faster the shutter speed the less light passes through the lens and onto the sensor. The slower the shutter speed the more light passes through the lens, but if there is movement in the scene motion blur may occur depending on the speed of the movement, your field of view and the speed of the shutter. So Shutter speed is controlling two things the amount of light and whether or not things in motion, including your hand, create a blurred image.
How do you know the Shutter Speed?
On most cameras, you will see the shutter speed on the barrel of the lens, in the Electronic View Finder, on the back of the rear screen and occasionally on a small screen on top of the camera. The numbers in most cases are fractions such as 1/2 which represents half a second or 1/60 which represents one-sixtieth of a second. In the diagram below you can see the typical range of shutter speeds on the left. The chart only lists full stops, so every stop means either a halving or doubling of light.
Avoiding a Blurred Image on 50mm lenses or less
There are two things you need to consider if you wish to avoid blurring in your image. The first is no matter how still you think you are holding your camera there will be a slight shaking coming from your hands. This shaking will either soften the resolution of your image or blur the image. Typically most people can hold a camera steady somewhere between 1/60 to 1/125 with a lens whose field of view is 50mm or less. I have found with higher-resolution cameras I have a better result at 1/125. If your camera is new you may need to run a test to see what speed works for you. Keep in mind if you are using an APSC camera and not a full-frame then 35mm is equivalent to 50mm.
Avoiding a Blurred Image on 50mm lenses or Greater
When dealing with a telephoto lens the rule usually followed is to use the focal length to set your shutter speed, in other words, if you are using a 200mm lens then the speed should be no slower than 1/200. Keep in mind this is not a perfect rule and higher-resolution sensors may need a higher speed or the shakiness of your hands may require a higher speed. So it is important when you get a new lens to do your own tests and decide for yourself where you need to set the minimum speed.
Avoiding Blurred Subjects that are Moving in the Image
In most images, things can move, whether it is leaves in the wind or cars moving in the street so it is important to understand what speeds might freeze these movements. The chart below gives you a rough idea of what speed is appropriate for subjects that are moving.
Image Stabilization and In Body Image Stabilization IBIS
Many telephoto lenses have image stabilization to help reduce the camera shake from your hands, this may help you reduce the speed you use depending again on how steady you hold the camera. This usually helps reduce up and down and left and right movement or two axis of movement. Newer cameras, especially mirrorless cameras now have In Body Stabilization (IBIS) which controls for 5-axis: adding pitch, yaw and roll. The Sony A7R V for example advertises an eight-stop advantage using the IBIS system in the camera. This means if you can hold the camera steady at 1/125 with a 50mm lens you should be able to reduce your speed to 2 seconds, however, I have not been able to get this sort of advantage from my IBIS system. In addition to this as the telephoto lenses can, depending on their field of view, magnify camera shake to such a degree that the IBIS system does not work effectively. All that to say you need to test your camera to see what speeds work for you with your IBIS system on.
Keep in mind that IBIS does not freeze things moving in your image, so a moving bike at a low speed will still be blurred even though the rest of the image may be tack sharp.
Is Blurring Necessarily a Bad Thing?
As you can see in the chart above there are some times when a low speed works to your advantage such as fireworks, where slowing the shutter speed down to 2-8 seconds will capture more of the fireworks than a quick shutter. Often slowing the shutter down can give a softer look to clouds and water. There are also stylistic reasons why you might want to introduce some blur into an image, as you can see from the examples below.
2010, Gelatine-silver print, 16 x 20 inches, Phyllis Schwartz
Slow Shutter
Slowing the shutter down does allow you to do some interesting things with your camera on a tripod, as the images below illustrate.
Port Angeles Light, Edward Peck
