the exposure triangle explained

What is the exposure triangle?

A tip that’s often given to new photographers, is to study the exposure triangle. But what is the exposure triangle and why should I know about it? For a beginner photographer it might be an intimidating concept to grasp, but I’ll try to explain it as simple as possible. Let’s start at the beginning: a very important aspect of taking a photograph is light. Many say it’s even the basis of photography. Just looking at the word itself, “photo” meaning “light” and “graphy” meaning “writing”, photography is essentially “writing with light”.

In connection to the light we use in photography, there is exposure. Exposure is the amount of light that is cast onto the light-sensitive medium of the camera. It might sound complicated, but let’s break that down. Inside your camera is either a film (analogue) or a sensor (digital). The outcome of the picture is a result of how much light is shed onto the film or sensor and how light-sensitive it is. More light makes a lighter picture, less light makes a darker picture.

But my camera shows me if the exposure is right

Modern cameras have a built in exposure meter. This means that when you use the automatic settings of your camera, the camera will try to expose the photo correctly by automatically setting the parameters in a way that it thinks is best. If you use one of the partially manual settings of your camera, like aperture priority or shutter priority, then you can manually set some of the parameters. The camera will then automatically set the remaining parameters to achieve a correct exposure. In full manual mode, you’re on your own. In that case the camera will just accept your settings and not do anything to correct the exposure. So when exposure is off, you will end up with an underexposed or overexposed photo.

Then what camera mode is best to use? The one that you feel comfortable with! Using a (partially) manual mode gives you greater creative freedom, but if you don’t understand what you’re doing, you will still end up with bad pictures. Also, if you do know all the ins and outs, you are not required to always use the full manual mode. Sometimes it’s just more convenient to use a semi-automatic mode, for example in fast changing circumstances.

How exposure works

There are three factors that determine the exposure:

Shutter speed: regulates the amount of time the shutter opens, letting light into the camera and onto the film or sensor. So, selecting a short shutter speed only opens the shutter for a very short period of time, thus letting in only a small amount of light. On the other side, a longer shutter speed will open the shutter for a longer period, letting in more light. The shutter speed is measured in seconds, or a part of a second. Because it controls the time of your pictures, shutter speed influences the movement in your picture. You can use it stop or create motion in your photographs.
E.g. 1/4000s (one four thousandths of a second) is a very short or fast shutter speed, where 1s (one second) is a very long or slow shutter speed.
Aperture: I will explain more in detail about this in another blog, but the sort explanation is; this determines the size of the opening in your lens. Basically a larger opening lets in more light, and a tighter opening will let in less light. The important thing to know about aperture is, that a larger opening has a lower number and a smaller opening has a higher number. The aperture also controls depth of field in your photo. Aperture size is indicated with an f-number.
E.g. f/2 is a large opening letting in a lot of light, where f/32 is small opening letting in a small amount of light.
ISO: this controls the light-sensitivity of the film or sensor. When using a low light-sensitivity, you will need more light to fall onto the medium to get a correct exposure. Opposite, using a high light-sensitivity requires less light to get a correct exposure. This sounds easy enough, but unfortunately a higher ISO comes at a trade-off. It will introduce noise into your photograph, which could decrease the quality of your photo.
E.g. ISO100 is a low light-sensitivity, needing more light to fall onto the medium. ISO12800 is a high light-sensitivity requiring less light to enter the camera.

The triangle

This leads us to the exposure triangle. We have the three factors mentioned above, controlling the amount of light and the light-sensitivity, which in unison control the exposure of a photograph. Now the trick is, that changing on of the three will also affect the other two. This means when you have a correct exposure but you want to change one of the settings, most likely one of the other two will also have to be changed to keep getting a proper exposure. On the other hand, if you have a bad exposure, you can use your knowledge of the triangle to correct the exposure.

This all can be shown in a graphic way like the diagram below:

You can see our three parameters aperture, shutter speed and ISO are in the sides of the triangle. Alongside each side there are values that correspond with the parameters. The arrows in the middle represent the move from darker exposure to lighter exposure. For each setting it shows what a change in either direction will do for the exposure. The text on the outer ring of the triangle shows the artistic consequences of changing the settings.

How to use the exposure triangle to your advantage

By studying the exposure triangle and the dynamics behind it, you can learn what the effects of changing the parameters will be. Also you can figure out how you should change the setting(s) to get the desired effect. To exemplify, if you are experiencing underexposure (a dark picture) there are three things that can be changed for a better exposure:

Decrease your shutter speed to let in more light
Increase your aperture to let in more light (beware, a larger aperture is represented by a smaller number)
Increase the ISO to have a greater sensitivity to the light coming in

Another example, looking at it from an artistic point of view, could be that you are photographing a windmill. If you want to show the movement of the blades in your photograph, you need to slow down your shutter speed. The consequence of this would be that you let in more light, causing an overexposed image. The solution would be to either lower your ISO, or close down your aperture to correct the exposure.

You don’t have to use all of your options, but you are always free to use more one depending on your needs. It all depends on the conditions of the surroundings and the type of picture you are trying to take. To get the most out of photography you need to understand these three principals and how to use them to your advantage in every situation.

Conclusion

Mastering the exposure triangle, and the three components it is made up off, will help increase the quality of your photos. It will also give you options to showcase your creativity. Knowing how to manipulate the shutter speed or aperture to your advantage, will give you the power to create the type of picture you envisioned. If you keep practicing this, your photography will improve massively.

I hope I managed to shed some light on the situation with this blog (pun intended). If there are still things that are unclear, don’t hesitate to ask me for clarification. If there are any other comments you would like make regarding this article, you can also reach out to me in the comment section below!