Understanding the Exposure Triangle

A lot goes into creating a quality image. It’s more than simply having an expensive camera. There are particular skills and techniques that can help a photographer get the most out of his/her camera.

We thought a discussion on the exposure triangle would be a useful exercise for this blog, as it is arguably one of the more important skills a photographer can posses. Nice composition of an aesthetically pleasing scene will almost certainly always be ruined by poor exposure.

Each image we make requires a certain quantity of light to expose it correctly. This piece is all about understanding the components to that exposure, as well as how to find the correct exposure each time.

The exposure triangle is a common way of associating the three variables that determine the exposure of a photograph: aperture, shutter speed, and ISO.

A skilled photographer really must balance all three of these to achieve a desired result. It shouldn’t be luck that defines success with this aspect of photography. Save luck for catching that perfect sky, right at sunrise, precisely on the day that you happen to be standing on a perch with perfect aim at Half Dome towering over the Yosemite Valley. That is luck (and probably putting in a lot of time, but that is for a different post)!

After reading this blog, we hope that you’ll be able to find perfect exposure without the need for luck.

Aperture, shutter speed and ISO make up each side of the exposure triangle. Let’s discuss these individually, first:

Aperture

The first side of the exposure triangle is aperture.

Aperture is the size of the circular hole in the lens. A wider aperture is going to be achieved by setting your camera to a lower f-number. A narrower aperture, which will allow less light to the sensor, will be achieved using a higher f-number.

As landscape photographers we’ll typically want less light to reach the sensor because we are often looking for larger depth of field. Depth of field is a byproduct of aperture. Narrower apertures (higher f-numbers) give a greater depth of field, allowing more of a scene to be in focus. So, imagine for a moment that you are travelling with us on our Canyons of Utah: Zion and Bryce Tour, and we are perched to capture the Watchman in Zion National Park. If your desire is to take in that landscape with your image, you’ll be looking to use narrower apertures (higher f-numbers) to create a wider depth of field for that image.

 

 

If you were looking to close in and isolate a hoodoo, or a series of hoodoos, then you would choose wider apertures (lower f-numbers) to create a narrow depth of field, which can help isolate your subject, such as Russ did in the below image.

Shutter Speed

The next side of the exposure triangle is shutter speed. Shutter speed is a measure of how long the shutter remains open correlating with how long the sensor is exposed to light. A lower exposure is achieved by using a faster shutter speed because it has less time to collect light. Conversely, a slower shutter allows more time for the sensor to collect light, thereby resulting in a higher exposure. So, say you are entrenched up on Barter Island, taking photos of polar bears playing with each other as they frolic across the arctic sea ice. You may look to stop motion by using a higher shutter speed. If your shutter speed is too slow, your camera will record the movement which will result in your subjects being blurry, thus your image being deleted as opposed to framed and hung on your living room wall.

ISO

The last of the exposure triangle is ISO. Making adjustments to ISO is controlling the digital sensor’s sensitivity to light. The lower the number ISO you choose, the less sensitive your camera is to light and the finer the grain. Conversely, the higher number ISO you choose, the more sensitive you camera’s sensor becomes to light, which allows you to use your camera in darker situations. The cost of doing so is a more grainy image.

So, why would we use a higher ISO? You’d really only want to use high ISO if you have to. If you find yourself at a point where you are already utilizing your widest possible aperture and the slowest shutter speed, yet something still needs to be done. Use a higher ISO rather than sacrificing sharpness for a slower shutter speed.

(click graphic for larger Image)

Putting it all together

Now that we know each side of the triangle, let’s put it together to see how aperture, shutter speed and ISO work in concert to produce a photo that is properly exposed. And keep in mind that if one of these variables changes, at least one of the others must also change to maintain the correct exposure.

Even if you haven’t previously heard of the exposure triangle, you may have heard the term ‘stop.’ It is crucial to know and understand what is meant by a stop of light. A stop refers to the doubling or halving of the amount of light that makes up an exposure. Adding a stop of light by doubling the exposure will brighten an underexposed image. Conversely, decreasing an exposure by one stop will darken an overexposed image.

So how do we do this?

To do this, we need to change the aperture, shutter speed, and/or ISO. So let’s us look at each of these individually.

In order to add one stop of light, you’d want to double the shutter speed to do so. So, going from ⅛ to ¼ would double the exposure, increasing a stop of light. Increasing your exposure from 1/1000 to 1/125 would be three stops because it is one stop to go from 1/1000 to 1/500. Then a stop to go from 1/500 to 1/250. Then another from 1/250 to 1/125. Get it? This one is rather easy, actually, compared to what is coming up next.

F-stops, which relate to aperture, are when math stuff can start to kick in, and really who wants to do math? Not I. Perhaps do what you may have done in school and simply memorize the sequence! In the following sequence, each f-stop represents a decrease of one stop: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22.

So what does that mean? If you change your shutter speed down a stop, then you’d better change your aperture up a stop. Or, one stop each between aperture and ISO.

Like shutter speed, ISO makes basic mathematical sense. Doubling the ISO is one stop increase in exposure. Halving the ISO is a reduction of the exposure by one stop.

Back to the simple life, no?

We hope that you take these tips out into the field with you next time you head out in order to get a nice grasp on the components of getting perfectly exposed images going forward. If you already know the exposure triangle, we hope this may have been a nice refresher!

Kenton Krueger

 

 

 

 

 

 

Kenton Krueger has spent the past several years guiding guiding backpackers, hikers and photographers into the wild places of the American West such as Havasu Falls, Grand Canyon and Yellowstone National Parks as well as in the Grand Staircase Escalante in southern Utah. In addition to backpacking and camping, his adventures include rock climbing, exploring the slot canyons of southern Utah, mountain biking, and bagging 14ers in Colorado’s San Juan Mountain Mountain Range. Kenton is a trail runner, former pilot, newspaper photographer and writer. Kenton looks forward to utilizing his years of guiding experience, combined with his passion and experience behind the lens to provide memorable and unforgettable experiences at the wild places we will visit together.

1 reply
  1. Kerry
    Kerry says:

    Thank you so much! I am relatively new to photography and have talked to two professional photographers who have given me two different responses to this question: should all of this be in manual. One of them (who has a gallery in Hawaii) utilizes the camera’s “brain” to do some of this thinking for him. He will use one of the three in a fixed mode so that it get priority, and allow the camera to adjust accordingly. His theory is that the camera has this powerful brain that can adjust far faster than he can, allowing him to capture an image quickly rather than lose it while adjusting (maybe the moment a wave crashes and the foam of the surf is just right). The other photographer (specializes in photographing children in highly artistic settings) believes that heresy. She does straight manual. Would love your thoughts on this!

    Reply

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