The simplest explanation of Shutter Speed on the internet

Having looked at the concept of aperture and depth of field, the next crucial function to understand in the operation of a camera is shutter speed. As the name suggests, shutter speed is the measure of the time the shutter is open when taking a photograph.

The aperture controls the flow and intensity of the light through the lens. The length of time the shutter stays open controls how long the light hits the sensor or film to create an appropriate exposure.

The fireworks explode and the glowing particles move outward rapidly. This is a fairly long exposure at 1 second; it shows the distance the particles moved during the exposure. The camera was on a tripod to hold it still.

The Shutter

The shutter is a very thin, light-tight curtain in the camera body that sits between the lens and the sensor or film. When the camera is fired, the shutter stays open for a measure of time that is set with the shutter speed dial. The speed settings of the shutter are straightforward to understand as they are expressed in seconds or fractions/parts of a second. Generally, the preset speeds range from 30 seconds right up to 1/8000th of a second. When on B or “bulb” setting the shutter can be kept open manually for any length of time you choose. This would be useful for shooting night skies or in very low light conditions.

As always with photography, there is a myriad of possible treatments for every situation, so remember none of the information in these basic tutorials is definitive. There is always an exception to the rule. Your job is to find what works for the subject in front of you!

To make an appropriate decision for shutter speed a few things need to be considered. How still is the camera? Is the subject moving, and if so, how fast? Do I want to show a moving subject frozen still or blurred?

Images taken at less than 1/125th of a second can easily suffer from camera shake which a blurred image because the camera moved during the exposure. To avoid camera shake, the camera is either held very still or on a tripod. Images taken at speeds longer than a 1/60th of a second will almost always need a tripod or monopod. You can brace yourself against a wall or a tree as well. Think laterally and use whatever is at hand that could offer stability.

Balancing act

Just so you get a handle on the principles, if the first diagram below represents a correct exposure using a midrange aperture, the next two diagrams illustrate how changing the aperture effects shutter speeds. Because the shutter speed is being adjusted equally to accommodate the aperture all three settings would create an identical exposure with pronounced differences in the depth of field in the photographs. A fundamental thing to know at this point is, every full F stop is of equal measure to every full step in shutter speed and every full step in ISO (sensor sensitivity). The three work as an interlocking system, each full step being of of equal value or measure. This means you can maintain an exposure you want and still make choices around shutter speed and depth of field.

Shallow Depth of Field

Aperture with a small number = large hole in the lens = shallow depth of field = less of the image appears sharp = more light coming into the camera = shorter shutter speeds

Deep Depth of Field

Aperture with a large number = small hole in the lens = deep depth of field = more of the image appears sharp = less light coming into the camera = longer shutter speed

If the aperture is changed by a stop the shutter speeds must be adjusted by a stop to maintain a correct exposure. The fact that aperture and shutter speed affect each other to such an extent is the compromise that underpins many of the decisions you will need to make in photography, but more about that later. 

Freeze!

Let's look at the ideas around freezing motion. If it’s important to capture sharp detail the shutter needs to be opening and closing faster than the movement of the subject. The faster the subject, the faster the shutter speeds will need to be. Getting a sharp image of someone walking may work at 1/125th of a second, whereas the speeds needed to shoot a racing car or to freeze the ball from a tennis serve will be upward of 1/2000th of a second.

This image was taken at about 1/2000th of a second.

Blur’s Greatest hits

To achieve a controlled blurring of motion in a photograph will take some experimentation. This is one of the huge benefits of digital cameras as you get to see the results and make adjustments to suit your desired outcome. As an example, let’s say we are shooting the inside of a building. Set up the camera on a tripod and with a deep depth of field (small aperture) to take a relatively long exposure of ½ a second. The camera is in a fixed position and the subject is static so all going well our photograph would be sharply in focus. So, what if whilst we were taking a ½ a second exposure you got someone to walk through the shot? In a ½ a second they could take a good stride. The photo would still show the inside of the building in sharp detail because the camera and the building are still. It would also show a blur across the image starting where the person was when the shutter opened and finishing at the point they reached when the shutter closed. To show more detail in the moving person you can open the aperture slightly, which in turn will allow you to speed up the shutter or get the person to move slower through the frame. This long exposure of a moving subject is how that “cotton wool” effect is achieved when shooting the movement of water over a waterfall. The droplet is shown as a blur as it falls or splashes.

This image was taken at about a 1/4th of a second. A tripod is the go at these slow speeds.

ISO/ASA

I should mention that the camera’s ISO function is the control of the light sensitivity of the sensor. It’s basically the same as ASA/film speeds, which is its measure of sensitivity or “speed” of the film. As you increase light sensitivity there is an increase in the pixelation/noise in digital or grain in film. At really high ISO an image will lose some of its smooth tonal gradations and some detail becomes pixelated. This is particularly obvious when images are enlarged. Remember that aperture dictates shutter speeds and vice versa. If you change the ISO of the camera to a faster setting or use faster film you can maintain small apertures and get faster shutter speeds. The whole deal is a compromise hinged on the decision you make about what you need from the photograph.

50 – 200 ISO = fine detail

400 – 800 ISO = fair detail, faster shutter speeds

1600 – 6400 ISO = compromised detail, very fast shutter speeds

The thing to remember is that there is no such thing as a perfect setting for all photography. There are a series of choices or options for different situations.

Experimentation is the key, shoot subjects in a wide variety of ways and let the process lead you down new paths. Understanding how to drive a camera is an accumulation of a lot of photography in many and varied situations. Actively applying this information whilst it is fresh in your mind is the way to convert it from information into your knowledge base.