What is the Exposure Triangle?

EmeraldHike

Well-Known Member
  • #1
Out of all photography topics out there, this one is my favorite. I love teaching others about the theory behind what we do and if I can help someone understand this simple concept, I think they'll run with it. The ideas behind the exposure triangle, while seemingly daunting early on, are actually rather simple. Once a budding photographer is able to grasp how light reaches a camera's sensor, the faster they'll excel at the hobby or profession.

There are three parts to the exposure triangle. They are aperture, shutter, and ISO. Each affects either how much light is able to reach the camera's sensor or how the sensor reacts to the light that reaches it. Two of these parts are physical, meaning they're mechanical aspects of the camera or lens, and one part is electronic, meaning it doesn't contain any moving parts; it's controlled by circuitry.

Each of the three parts of the exposure triangle are simple to explain and are rather straightforward concepts. The aperture is contained in the lens. It acts like the iris acts in an eye. It shrinks and grows, depending on how small or large either the camera or the photographer wants. The smaller it is, the less light that passes through the lens into the camera. The larger, the more light that passes through. It's that simple.

The camera's shutter is situated directly in front of the sensor inside of the camera itself. It's a plastic or metal shade that moves away and exposes the sensor when the time is right. The length of time the shutter moves out of the way is called shutter speed. The longer the shutter is out of the way of the sensor, the more light that's able to touch the sensor. The less the shutter is out of the way, the less light that's able to pass.

The ISO controls how sensitive the camera's sensor is to light. It acts sort of like a stereo amplifier acts. As you turn up the volume on an amp, the sound gets louder. As you turn the volume down, the sound gets quieter. As you turn up ISO values, the more sensitive the sensor becomes. As you turn the values down, the less sensitive the sensor becomes.

The main crux behind learning photography is learning how these three parts of the camera work together. For every change you make in one part of the triangle, another is affected. Everything is a negotiation in photography. These negotiations can be frustrating, yet rewarding and fun.

Aperture sizes are represented in f-stops. If you've been learning about photography for any length of time, you surely have heard of these. Basically, each f-stop you hear of is just another size of the aperture hole. Lenses vary in the number and sizes of f-stops they offer, but some sizes are standard. Take a look at the graphic below to get an idea of what aperture sizes look like.

FboDXKmLgXgSMfmjEuLf6C-1200-80.jpg
Thank you TechRadar.

In a typical lineup, each f-stop is either a doubling or a halving of light that passes through the lens. If you start at a large aperture size and go to a small size, you'll be halving each step of the way. These sizes are f/2, f/4, f/5.6, f/8. f/11. and f/16. Larger hole sizes are represented by lower f-stop numbers, such as f/1.2 and smaller hole sizes are represented by higher numbers, such as f/22.

Shutter speeds work similarly to aperture sizes. For each "stop" in a shutter speed, there is either a halving or doubling of light that's allowed to pass through to the sensor. Typical shutter speeds range from 30 seconds to 1/4000th of a second. Take a look at the following graphic to see how slower and faster shutter speeds can affect the exposure of an image.

speedvalue_1.jpg
Thank you B&H.

A camera's ISO is set in stops as well. The ranges of ISO values are varied from camera to camera, but they usually start at a low number (and sensitivity) like 100 and climb all the way up to 16,000 (high sensitivity) and higher. Again, each stop is either a halving or doubling of sensitivity (exposure), so an ISO 100 is half as sensitive as ISO 200 is.

These are the basics of the exposure triangle as it pertains to photography. There's much more to each of these areas, but for now, this is plenty to chew on if you're new at this. Going forward, we'll discuss how each change in any one of these aspects can alter the outcome of a photo. I'll talk about the goods and bads of altering aperture, shutter speed, and ISO.
 
Top