This series of articles is excerpted from Rocky Nook’s Enthusiast’s Guide to Exposure by John Greengo covers the controls — shutter, aperture and ISO. The week, John explains how to use the shutter to stop action.
Camera shutter speeds
Most cameras have shutter speeds that range from 1/4000 to 30 seconds, with some models extending beyond these settings. In terms of exposure, shutter speeds are a great way of controlling the amount of light entering the camera, since every camera has so many from which to choose. Beyond using shutter speeds for exposure control, we can also use them to affect the look of moving objects in the frame. Moving objects can be rendered either frozen or blurry depending on the chosen shutter speed and the movement of the subject.
What is a fast shutter speed?
A fast shutter speed is one that is quick enough to freeze the motion of a moving object. Generally speaking, shutter speeds of 1/30s and longer can be considered slow; speeds of 1/250s and shorter can be considered fast. For fast human action, like running or dancing, 1/500 should freeze the action. With casual human motion, like walking or talking, 1/60 will likely do a good job at stopping the motion. These examples are very general rules of thumb, and there are many exceptions. Your average runner going through the local park will likely be frozen with a shutter speed of 1/500s, but a professional athlete may need 1/1000s or 1/2000s. For a slug moving through the garden, a shutter speed of 1/30s may do a perfectly good job. The concept of a fast shutter speed is all relative to the motion of the subject, but 1/250s and faster is a good rule of thumb.
Right and wrong shutter speeds
When it comes to right and wrong shutter speeds, it all depends on the desired outcome of the photographer. Don’t ask another photographer what shutter speed to use unless you are trying to get your photo to look just like theirs! Sometimes we want our subject to be frozen so that we can clearly see every detail, from the shoelaces to the hair blowing in the wind. Other times we want to create a more artistic abstract of a moving subject with the blurred lines showing their movement during the exposure.
The best fast shutter speed
For subjects that move, there does seem to be a best fast shutter speed and a best slow shutter speed. The best fast shutter speed is the slowest one that clearly stops the motion of a subject. If you want to freeze the action of a subject, you’ll use a faster shutter speed, possibly 1/250s or faster. If the subject shows movement or looks blurry at 1/250s, go to the next faster shutter speed of 1/500s. Continue that experiment until you get to a shutter speed that will clearly freeze the motion of your subject. An overly fast shutter speed will certainly stop the motion of the subject, but it also lets in less light, meaning you’ll have to compensate by changing the aperture or ISO setting.
Let’s take the example of a runner that could be frozen at 1/500s. In this case, let’s say that 1/500s is doing a perfectly good job freezing the action. For the rest of the exposure, suppose we have an aperture of f/4 and an ISO of 100. Suppose we now change our shutter speed to 1/8000s to stop every last bit of possible motion. What’s the effect? Going from 1/500s to 1/8000s is 4 stops of light less. In other words, our image just got 4 stops darker and we’ll need to compensate for this by changing either the aperture or the ISO, or a combination of the two. We could open up the aperture by 4 stops (f/4 to f/2.8 to f/2.0 to f/1.4 to f/1.0), but there are very few f/1.0 lenses available, so this is an unlikely option. We could make our image brighter by raising the ISO (ISO 100 to 200 to 400 to 800 to 1600), which would compensate for the 4-stop change. The problem here is that sensors will have more noise at ISO 1600 than they will at ISO 100 and our image will not be as clean and smooth in detail as a result.
Back to our running subject, which was frozen at 1/500s: by going to 1/8000s to freeze more action, we’ve lost 4 stops of light. If you recall, we said 1/500s was doing a perfectly good job of freezing the action, so going faster would have no discernible benefit. Losing 4 stops of light does cause a negative impact on our other settings. Changing the aperture to compensate may not be a viable option, and changing the ISO results in a noisier image. A 1/500s shutter speed is the best fast shutter speed in this case because it sufficiently stops the motion of the runner and allows the aperture and ISO to be set with optimum settings.
Read excerpts from other Rocky Nook Enthusiast’s Guides.