When a camera takes a photo, the camera opens its shutter and allows light in through the lens and into the sensor which is then made into an image. There are three settings on your camera which will help you to determine how much light you want to let in. These settings are: Aperture, Shutter Speed, and ISO— also known as the exposure
triangle. Note: all three settings work together, so modifying one will mean you have to modify another in the opposite direction.
Before we go any further, I want to define the term exposure. Exposure is referring to the brightness or darkness of a photo—when we refer to an image as overexposed, we are saying the image is too bright (too much light was let into the camera’s sensor) and when we refer to an image as underexposed, it is describing the image as too dark (not enough light was let into our camera’s sensor).
Photography is all about controlling and capturing light. Most beginners think the magic of photography happens in the body of a camera, but the true source is light. A well-lit subject can still be captured poorly; light is everything.
Let’s go into a bit more detail on each of these settings:
Aperture: This is the size of the lens opening and they are often displayed in the form of f/8, f/5.6, etc. The smaller the number, the bigger the lens opening (or wider the aperture) and the more light is let into
your camera. In addition, aperture also effects depth of field (which will affect how much of your images is in focus).
Shutter Speed: This is how long the shutter is left open and are often displayed in the from of 1/60, 1/250, etc. The slower the shutter speed, the more light is let in. Shutter speed also affects you’re camera’s sensitivity and ability to stop motion. The slower your shutter speed, the more motion blur your image will have.
ISO: Your ISO is how sensitive your camera sensor is to light and is often display in the form of ISO 200, ISO 1600, etc. Higher ISOs will allow you to take photos in darker situations. Note: the higher the ISO more the noise or ‘grain’ your image will have.
In addition to determining the amount of light allowed on your camera’s sensor, these settings also control different photographic criteria as well and need to be taken into consideration before making any final artistic decisions. Aperture changes the depth of field, shutter speed stops motion or can introduce motion blur, and ISO modifies the noise levels of your images.
Now the exposure triangle is important to understand to help you take the photos you envision. It is an in-depth topic which we will dive more deeply as time moves on, but before we do it is important to understand the basics.
For a visual representation of how these three settings interact with one another, check out this website: http://photography-mapped.com/interact.html. Or check out the image below from lifehack.org. Either one will help you to visually see the changes the choices you make with these three settings will have on your exposure.