The Exposure Triangle: Understanding Aperture, Shutter Speed and ISO
Hello and welcome to another tutorial from my photography blog, teaching you the basics and essentials that will help you to develop your skills and become a master photographer!
In this blog post, we will be covering the core theory that will apply to every photo that you have ever taken and will take in the future; How your photos are exposed. By mastering and understanding this basic theory, your shooting will not only drastically improve, but you will find that you have greater control over how you expose your photos in every possible situation.
The above diagram, known as “The Exposure Triangle”, demonstrates how your camera’s Aperture, Shutter Speed and ISO settings work together to correctly expose your image. In case you’re wondering, “exposure” essentially means how much light is being let into the camera’s sensor. Each of the three elements, when either increased or decreased in value, will allow more or less light into the camera, therefore directly effecting the overall exposure of the shot.
For example, (as shown in the Exposure Triangle) the lower you set your Aperture, the more light you let into the camera. Therefore, your image will gain more exposure. However, changing your aperture will also affect your “depth of field”. Bare this in mind as we delve into each of the three elements; when you change either the Aperture, Shutter Speed or ISO to correctly expose your photo, you will also be affecting another component of your overall composition. Let’s take a look at that in further detail, shall we?
As we discuss each section of the Exposure Triangle, ensure you keep referring back to the diagram, for a visual aid of what it is we are looking at!
The Left Edge: Aperture
The Aperture is essentially a measure of how wide the cameras Iris is. A wider aperture (also known as a lower “f-stop“ or f-number, such as f/1.4) will let more light into your camera sensor, simply because the Iris is opened wide. A narrow aperture (also referred to as a higher “f-stop” or f-number, such as f/22) will let in less light into the camera, as the Iris is now no longer wide open.
Therefore, the lower you set the aperture, the more light you let into the camera. The higher you set it, the less light you let in.
However, changing the Aperture will also affect your “Depth of Field”. This refers to how much of your image is going to be sharp and in focus. A narrow aperture (e.g. f/16) will result in more of the image being sharp and in focus (larger apertures are therefore commonly used for landscape photos).
A Wider Aperture (e.g. f/2.2) will lead to less of the image being in focus. Lower apertures are frequently used for portrait work, keeping the subject sharp while blurring the background or elements in the foreground.
The diagram below demonstrates how changing your Aperture will affect the depth of field in your image.
IN CONCLUSION: When directly changing the Aperture on your camera, remember:
LOW APERTURE = MORE LIGHT/LESS DEPTH OF FIELD
HIGH APERTURE = LESS LIGHT/MORE DEPTH OF FIELD
The Bottom Edge: Shutter Speed
The Shutter Speed is a measurement of how long your camera shutter is left open for. The longer the shutter is left open, the more time the camera’s sensor has to collect light. Therefore, if the camera’s shutter speed setting is set to 1/1000 (one thousandth of a second), the camera will not have much time to capture much light. But, if the shutter setting is set to 5” (5 seconds), the camera will let in more light, creating a greater exposure for your image.
Changing your Shutter Speed however, will also affect the sharpness of your image. For example, if you are shooting a moving object (a car, wildlife, people walking etc.) you will want a higher shutter speed to freeze their movement and keep them sharp. Such as 1/1500 (fifteen hundred of a second)
On the other hand, if you are shooting a river and want to blur the movement of the water, you will want a slower shutter speed to create that blurred effect, such as 3” (3 seconds).
The diagram below shows how changing your Shutter Speed will create either frozen frames or blurred movement in your images.
IN CONCLUSION: When changing the Shutter Speed on your camera, remember:
FASTER SHUTTER SPEED = LESS LIGHT/GREATER SHARPNESS
SLOWER SHUTTER SPEED = MORE LIGHT/LESS SHARPNESS
I have written a separate blog post on Shutter Speed and the various techniques that you can apply to your photography for a range of effects in your photos. Click on the link below to check it out!
The Right Edge: ISO
Last, but certainly not least, we have the ISO. In a nutshell, the ISO is a post-image gain of the signal in the camera. But, the easiest way to think of it is as the “sensitivity of the camera sensor”. When you increase the ISO to a higher value (e.g. 2000) you are forcing the camera to create exposure with electrical signals instead of natural light. Unfortunately, in doing this, you will also increase the noise and grain in the image. That’s why it is important to always try and keep the ISO as low as possible (ISO 100 is usually the lowest setting on most DSLR’s). The lower the ISO, the less noise and therefore the sharper the image will be.
However, there will be situations in which you will need to raise your ISO value in order to correctly expose your image. An example of this would be a situation with very little light, where you have already lowered your Shutter Speed and Aperture to the maximum before compromising the sharpness of your image.
The diagram below demonstrates how raising your ISO will result in a noisier, grainer image:
IN CONCLUSION: When directly changing the ISO on your camera, remember:
LOW ISO = LESS LIGHT/LESS GRAIN
HIGH ISO = MORE LIGHT/MORE GRAIN
Putting it Together: “Stops” in Exposure
To correctly expose your image, you will need to decrease and increase the Aperture, Shutter Speed and ISO settings so that they coincide together harmoniously for the picture you are taking. When these three elements are combined together to expose your image, it is referred to as the “Exposure Value” (EV).
As we have briefly mentioned before, each of the exposure elements are measured in “stops”. For example, “Stops” in Aperture include 1.8, 2.0, 2.2 etc. For Shutter Speed, they include 1/100sec, 1/125sec, 1/160sec etc. For ISO, they include ISO 100, 125, 160 etc. These “stops” are basically “steps” up or down in the amount of light being let into the camera.
If your image is too dark and under exposed, you may want to decrease your Shutter Speed (for example) by 2 stops to let more light into the camera. Of course, it all depends on the image you are taking. If you are focused on shooting light trails and night, you will want to leave your Shutter Speed as it is and raise either the Aperture or ISO by two stops to let more light into the camera. If you’re shooting a portrait, you may be happy with your Aperture settings and want to change either the Shutter Speed or ISO for more exposure in your image.
TIP: Most DSLR camera’s will have an Exposure meter for you to view that will give you an idea of how well the image is exposed. Some cameras will display them in the menu on the screen, while others will have them in the viewfinder, below what the camera is looking at.
If the little squares are all the way to the left on the meter, the image is under exposed. If they are all the way to the right, they image is over exposed. You are aiming to have no squares heading left or right of the centre point in the meter. If there are no extra squares (except for the one under the “0”), then the shot is near enough exposed correctly.
This is a nifty tool to use before taking your photo to judge the exposure of the image. You can then adjust the stops in either your Aperture, Shutter Speed or ISO accordingly to expose your image.
OVER TO YOU
Now that you know the basics of the Exposure Triangle and how each element will individually affect how your image is exposed, its time for you go out and practice. Find different situations with different lighting and chop and change your Aperture, Shutter Speed and ISO settings to see how they affect the exposure of your shots.
Understanding these elements is a crucial part to mastering the composition and lighting of your photos, so once you have it down, everything else will become easier. So, get out there, flip your camera into Manual Mode (don’t be scared, you can do it!) and experiment with the three sides of the Exposure Triangle in your photos!