In camera, shutter speed, ISO and aperture are the three most basic tools to help you control the exposure. These three elements work together in what is known as the exposure triangle, which explains how all three components are related. When the shutter speed, ISO and aperture are all balanced, it creates a perfectly exposed image. This week, I will break down the basics of these three tools and explain how all three are important in changing the brightness or darkness of an image.
Shutter Speed
In its most basic form, shutter speed controls the amount of time allowed for light to enter the camera. The faster the shutter speed, the less time there is for light to enter; the slower the shutter speed, the more time there is for light to enter. In technical terms, the shutter is a small ‘curtain’ in the camera that rolls over the sensor, controlling how much time is allowed for light to hit the sensor. The easiest way to remember what shutter speed does is to remember that the ‘speed’ is equivalent to the amount of ‘time’ you expose the image. A quick shutter speed will give less time for light to hit the sensor, producing a darker image; whereas a slow shutter speed will provide more time for light to hit the sensor, producing a lighter image. It also controls how much motion blur is in an image.
You can see this in the example below. The left image was shot at 1/160 sec, freezing the motion of the waves. In contrast, the right image was shot at 1/4 sec, not only blurring the motion of the waves so they appear more smooth, but also producing a lighter image.
In simple terms: fast shutter = less light, less motion blur.
slow shutter = more light, more motion blur.
Aperture
The aperture also controls how much light enters the camera through a set of blades in the lens. The blades open and close, acting in a similar way to the pupils in our eyes. When they are wide open, they allow more light in; a smaller opening means less light is let in, the same way our pupils adapt to bright and low light! In basic terms, a wide aperture will let more light in, while a narrow aperture will let less light in. The aperture is set in f-stop numbers and the lower the number, the wider the aperture.
The depth of field is also controlled by the aperture. While a wide aperture (low number) will let more light in (brighter image), there will be less in focus, producing a shallow depth of field. Whereas a narrow aperture (high number) will let less light in (darker image), but there will be more in focus, producing a higher or ‘full’ depth of field. Below, you can see the left image, which has an aperture of f/4 (wide), has a blurred background, whereas the foreground is in focus, creating a shallow depth of field. In contrast, the right image has a slightly narrower/higher aperture of f/9, resulting in more definition and focus in the background in comparison to the wider aperture, so the depth of field is higher/fuller.
This can be quite confusing to get your head around, I still get confused myself sometimes! So I’ve found this diagram online from Improve Photography which explains visually.
ISO
I have left ISO until last, as it is typically the last thing you would change if your exposure still wasn’t correct for your liking. This is because it controls how sensitive your camera is to light. A higher ISO such as 1,600 will produce a much brighter image, but it will also create an image with a lot of noise. Noise is obvious when your image looks grainy, in a similar way to how photographic film carries grain the higher the ISO it is. Naturally, using a lower ISO number, ideally 100, is preferred to prevent grain on your images. This is the primary reason why changing the ISO number is a last resort to correct the exposure.
Cameras have varying levels of noise they can handle. You will notice that images you take with your phone at night often look slightly grainy or just not their best. That is because the phone is trying to compensate for the lack of light, creating more noise. Entry level cameras can typically handle an ISO of around 400 maximum, while pricier cameras can handle much higher levels. Each camera is different, so test your camera at increasing ISO levels to gauge the maximum ISO you can shoot at without your images looking too grainy.
Putting it all together
You might be wondering why you can’t just change one of the settings. The reason is because creating an exposure takes a balance of all three settings. You don’t want to overcompensate with a slow shutter speed to create an image with full depth of field, because it would result in a lot of motion blur. Additionally, you don’t want to overcompensate with a high ISO because you want to freeze motion with a fast shutter speed, or you’ll end up with noisy images. Below I provide an example of balancing the three elements together to create an exposure.
For this image, I wanted the entire shot in focus, so set my aperture at f/22 to get a full depth of field. Naturally, this created a very dark image! This also made the water quite choppy, which I didn’t want. Instead I wanted the water to appear smooth as it made its way around the rocks down the waterfall. To counteract the darkness of the image, and motion of the water, I lowered my shutter speed to 1.3 seconds. This made the water much smoother, creating a contrast between the sharpness of the rocks, and the movement of the waterfall. However, the image was still on the darker side. The last setting available to adjust was the ISO, which I increased from 100 to 200. With the three elements now balancing one another, I created the image!
Getting to grips with these three settings will help push you out of ‘auto’ mode and into ‘manual’ mode with your camera, and with this you will gain so much more control over the images you make! The final image shown just shows the importance of taking full control over your exposure settings and the potential images you can create. Once you understand how these three elements work together you can really start to get creative and experiment! Don’t worry about making mistakes, getting the balance can be confusing at first, but with practice comes progress.
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