March 14, 2014

Anyone who has spent any time around photographers or photography will have heard the term “the magic triangle”. This concept is vital, particularly if you want to step up from snapshot photography to taking really stunning images.

What is it?

The magic triangle is made up of three elements – shutter speed, ISO, and aperture – which work together to create an exposure by affecting how light comes into and is captured by your camera. Let’s look at each of these settings and what they do:

  1. Shutter speed is how fast the ‘curtains’ over your camera’s sensor open and close.
  2. Aperture is the diameter of the opening inside your lens.
  3. ISO represents the sensitivity of your camera’s sensor, which can be adjusted (many cameras do this automatically for you unless you turn it off).

Each of these settings affects the exposure, but each also affects the image you capture. With me so far? I hope so!! Let’s talk about each setting individually and how it 1) affects exposure and 2) affects your image.

Side One: Shutter Speed

We’ll start here since most of us find this concept the easiest to understand and apply practically.  If you blink really fast, you don’t let much light into your eye, right? Meanwhile, if you open your eyes for a long period of time you let in lots of light. The same with shutter speed: a fast shutter speed lets in less light than a slow shutter speed.

How does this affect your image? It changes how you capture motion. A slow shutter speed gives moving subjects more time to blur. So if you need more light (slower shutter speed) you have to balance this with the ability to capture crisp subjects (faster shutter speed).

Side Two: Aperture

Hopefully this makes sense so far. Aperture is a measurement of the diameter of the lens opening, expressed in a fraction (like f/1.8 or f/5.6). A smaller number equals a larger aperture or opening, since it’s a fraction (f/2 [or 1/2] is bigger than f/8 [or 1/8]). So here a smaller number equals a larger opening, which in turn lets in more light.

Aperture affects depth-of-field – the amount of your image that’s in focus, from front to back. If you want a crisp subject with a blurred background for your next portrait, you want a large aperture. For landscapes where the entire image is in focus you want a small aperture, but remember that lets in less light.

Side Three: ISO Sensitivity

Imagine you are tasked with digging a hole, just you and your shovel, and this will take you one hour. If someone else comes to help you then that cuts the finishing time in half to 30 minutes, if two more people join you after than it’s cut down in half again to 15 minutes. This is how changing the ISO sensitivity works – it cuts down the time required to capture an exposure. You can increase the ISO when you are working with less light.

Likely you have already encountered the effect of high ISO – noise. Noise caused by high ISO results in a grainy appearance (or dark specks), so you need to balance its ability to get the shot with whether the shot is going to be usable due to noise.

Putting it Together

Each side of the triangle works with the other to create your exposure, so if you haven’t yet you should get used to using semiautomatic modes to control aperture or shutter speed, while your camera takes care of the rest.

In Part II of this article we’ll talk about not only how each setting affects your exposure, but also how it affects the other settings, and how you can use this to get the ‘correct’ or ideal image (as well as graduating to fully manual mode). For now, start practicing!


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