Understand the exposure triangle

Mats Learning Leave a Comment

If you’re getting into photography, there will usually be someone a little more experienced there who starts telling you about shutter speeds and apertures and maybe you even try to get it, but you just want to take pictures so what you’re told goes in through one ear and out through the other. Spend a little time learning this and i promise you that understanding exposure will forever change your photography and help you take better pictures.

On a physics level, photography is about capturing light waves. Things around us radiate or reflect light of different strength and color and that makes up our subject. A camera has three different ways to regulate light: ISO, shutter speed and aperture. These three parameters work in unison to make up your exposure. This is often called the exposure triangle.

Exposure triangle

It’s not a complicated as it sounds. Let me explain it in a few minutes.


Light comes in through your lens and is captured by a sensor, which processes the light into digital information. You can think of the sensor as an area covered with buckets. There might be 4000 by 3000 buckets or even more if you have a high-end DSLR camera. Each of these buckets collects light. Actually it also separates red, green and blue light, but we’ll leave that to some other post. One bucket will be one pixel in your final image. If you zoom in far enough in a digital image, you can see each individual pixel like this:


By changing your ISO value, you’re making the sensor more sensitive (higher ISO value) or less sensitive. The basic ISO value is 100 and you will usually have access to values 200, 400, 800 and on some cameras 1600 and 3200. Some advanced cameras will allow even higher ISO values.

When you find yourself taking pictures in low light situations, you can increase your ISO setting to make your sensor register more light. But there’s a flip side to this. The higher you take your ISO settings, the more noise you will get in your image. Noise means that some of the pixels are irregular either in its luminosity (too light or to dark) or in color, which makes it appear in a totally different color than the surrounding pixels. A noisy image taken at high ISO may look like this if you zoom in close:


So the conclusion is that you want to keep your ISO as low as possible. Find the ISO setting on your camera and experiment with it until you have an understanding of how it works. Find out what the maximum and minimum values on your camera are. ISO is usually set on a separate button on your camera or in the menu system. Get your manual out and learn exactly how it works. The effort will be well worth it

Shutter speed

The next parameter you can use to control light is shutter speed, sometimes called exposure time. This means how long the sensor will receive light. The camera opens the shutter and keeps it open as long as the shutter speed setting says. This can range from as short as 1/8000 of a second on some modern cameras up to 30 seconds. Many cameras also have the “B” setting (Bulb), which allows you to open the shutter and keep it open as long as you want.

The thing with shutter speed is that if it gets too long, you may get blurry images. This is because you, the camera or the subject moves while the shutter is open. As a rule of thumb, you want the shutter speed to be at least as short as the length of your lens if you’re hand holding your camera. So for a 50mm lens, you want 1/50 of a second or shorter shutter speed. For longer shutter speeds or telephoto lenses, you may need to put your camera on a tripod to get sharp images. Also, the closer the subject is, the bigger the chance of getting motion blur because your shutter speed is too long. This is because a moving subject closer to the camera will move more in relation to a more distant subject in the same amount of time.


Aperture is the third parameter. The aperture is a variable sized opening in your lens through which light flows while the shutter is open. With a small aperture, the sensor will get less light and with a bigger aperture, it gets more.

Aperture numbers are also known as f-number or f-stops and they are a little confusing. There is a logic to it, but we’ll leave that to some other post. What’s important is that you understand that a smaller aperture number means a larger opening and a larger number means a smaller opening. The maximum and minimum aperture values vary from one lens to another. The smallest aperture may be f16 or f22 and the largest may be f1.4, f3.5 or f5.6. This image shows some common aperture numbers and what they look like:


How to learn

So how do you learn all this? The best way is of course to get out and experiment with your camera. It depends on what camera you have, of course, but usually, there will be a dial with a few presets, an auto mode (dont use it or you’ll never learn!) and then the interesting stuff. Look for these three modes:

  • Aperture priority (A), where you choose the aperture and the camera selects a shutter speed
  • Shutter priority (S or Tv), where you select the shutter speed and the camera selects the right aperture
  • Manual (M), where you select both aperture and shutter speed

Camera dial

Get your camera out and start experimenting. Set up different situations and subjects and adjust parameters and see how they affect each other; how a larger aperture gives you shorter shutter speed in A mode, how a longer shutter speed gives you a smaller aperture in S mode and so on.

Test shooting moving subjects with different shutter speeds to see at what speed the camera can no longer take a sharp picture.

Shoot a still subject with increasingly longer shutter speeds to see at what speed you get blurry images from camera shake.

And don’t forget to experiment with different ISO settings. Try shooting in a darker environment and experiment with increasing the ISO value to still get a short enough shutter speed to get a sharp image. Notice how you image quality decreases from noise at higher ISO values. Learn what is the maximum ISO value at which your camera will give you an acceptable image quality.

Hey, please leave a comment and let me know what you learned and how it helped you take better pictures.


Lämna ett svar

E-postadressen publiceras inte. Obligatoriska fält är märkta *

Denna webbplats använder Akismet för att minska skräppost. Lär dig hur din kommentardata bearbetas.