What is the exposure triangle! And you are asking me? The exposure triangle… is the core of photography. And no, we’re not talking about how to give exposure to you work by combining a stunning photography website, engaging social media accounts, and impressive people skills. This is about empowering your creativity by translating your vision into an image.
Regardless of your skill level and preferred genre, learning how to control the exposure is a must to capture good photos. Even those with incredible post-processing skills will find that it’s nearly impossible to turn a badly exposed picture into a great photo. And the secret to nailing the perfect exposure is understanding how the exposure triangle works.
What is the exposure triangle?
Exposure triangle is the photography term that describes the relationship between the three elements that determine the exposure of a photo: shutter speed, aperture, and ISO. The way these three factors are balanced determines the final appearance of a shot and the feelings it evokes.
Knowing its importance, it shouldn’t be a surprise to hear that the exposure triangle is one of the hardest photographic skills to master. On the bright side, once you fully understand it there’s nothing you won’t be able to do.
Before we dive deeper into each of the variables involved, take a look at this visual representation of the exposure triangle and see how each side affects the image.
Measuring light in stops
The amount of light that reaches the camera sensor is measured in stops. This concept was created to unify the three elements involved, as each of them calculates different parameters. A stop doubles or halves the amount of light that reaches the camera sensor. Increasing one stop in any of the three variables results in twice as much light reaching the sensor. Decreasing one stop cuts the amount of light captured by half.
Depending on the camera that you are using, you might be able to work with 1/2 and 1/3 increments. While the creative flexibility might allure you to select this option right away, you should try to master the basics before increasing the difficulty of the task in hand.
If you’re used to shooting in semi-auto modes, you might have realized that these stops are what allow you to modify the exposure with EV compensation in Program, Aperture Priority, and Shutter Priority modes.
The first side: shutter speed
The only reason that we’re calling this the “first side” is because shutter speed is usually the easiest variable to understand. The shutter speed measures the length of time that the camera sensor is exposed to light. During this time, the shutter is open and the position of objects within the frame is captured. That means that if something is moving during the exposure, it will appear blurred on the image.
“Why would anyone want a blurred photo?” You may ask. Think about those stunning night pictures with light trails or the beautiful landscape photos that capture smooth rivers and waterfalls. Learning how to shoot in slow shutter speeds will allow you to see the world from a completely different perspective.
On the other hand, higher shutter speeds are used to freeze the action. This is especially useful to capture unique instants, such as a breaking wave, or avoid blurriness when you cannot use a tripod, like in underwater photography.
While each shot has its own requirements, here are some general guidelines on when to use different shutter speeds, from faster to slower:
1/500 to 1/2000: flying birds
1/250 to 1/1000: sports
1/250 to 1/500: children and pet photography
1 to 8 seconds: motion blurred water
20 to 30 seconds: clear stars
10 minutes and up: star trails (you’ll need to shoot in bulb mode)
The second side: aperture
Aperture is the size of the opening through which light enters the camera. The bigger the opening, the more light captured. The concept is just as easy to understand as shutter speed, if not easier. However, the way it works is slightly more complicated than its counterparts.
For starters, aperture is measured in f-stops. This unit is the result of dividing the focal length of the lens by the diameter of the opening. As numbers get higher, aperture becomes smaller and lets less light in. To make things a bit more complicated, the numbers are doubled every two stops – meaning that the amount of light is four times higher every time the number is doubled. This might sound incredibly confusing right now, but you’ll get the hang of it as you practice.
The other main challenge of mastering the use of aperture is understanding how it affects depth of field. Wider openings, lower numbers, result in shallow depth of field, making it a great tool for portrait photography. Contrarily, narrower openings offer a wider focus depth. The reason behind this is physics, and much too complex to be synthesized in a couple lines. For now, focus on mastering the exposure triangle. There will be plenty of time to find out why things work the way they do.
The third side: ISO
Last, but not least, is ISO which defines how sensitive the camera sensor is to the light that reaches it. In film photography, ISO is more of a constant than a variable as it depends on the film roll sensitivity and cannot be changed once it’s inside the camera. On the contrary, digital cameras allow photographers to easily modify the ISO. Technically, it would actually be more accurate to call it “post processing gain” as the actual sensitivity cannot be changed.
While the three variants of the triangle are given the same weight of importance and need to be balanced, the purpose of modifying the ISO is different than that of shutter speed and aperture. The first two variables are considered creative tools and have a direct effect on the aesthetics of the image. However, ISO is actually considered a way to balance the overall exposure to achieve the desired effect of the previous settings.
Essentially, you’ll want to increase ISO sensitivity when the values you need on shutter speed and aperture are not enough for a good exposure. One of the most clear examples is astrophotography, as it is necessary to use a high ISO in order to compensate for the appropriate shutter speed needed to capture gleaming stars.
The downside of increasing ISO is that it results in images with more noise and less detail. Because of this, it is recommended to stick to low ISO numbers in order to get the best results.
Getting the right exposure
No pressure, but there’s only one mathematically right exposure for each scene. Shooting above this value will result in overexposure and loss of detail on the highlights. On the other hand, shooting below it will crush the shadows and give an underexposed image. Even if you’re actively trying to get one of these effects, it is always better to aim for a balanced exposure in order to capture as much information as possible. After all, it is easier to modify exposure levels in post-processing than to create details that are simply not there.
The good news is there are hundreds of potential settings that can be used to achieve the perfect exposure. And each of them gives a completely unique result. It’s completely up to you to decide how to combine shutter speed, aperture, and ISO to capture the scene based on your vision.
There are two main ways to find the right exposure for a scene: a light meter and the camera histogram. A light meter is a photography accessory that allows photographers to measure the light and find the correct exposure settings based on their preferences. For example, you can preselect your ISO and shutter speed and use it to measure the proper aperture. In contrast, the histogram is built into your camera but might take a bit more trial and error. Simply aim for a balanced curve that extends across its whole length without cutting off at any point.
The most important thing when it comes to exposure is understanding that you must always balance the three variables of the exposure triangle. If you modify one of the settings, you must compensate for the additional or lost light by decreasing or increasing one (or both) of the others.
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