Exposure triangle for beginners /Understanding exposure triangle. What is it? How do you use it?
Basic Photography
Pixean
September 26, 2018

Whenever we talk of photography, the discussion about exposure follows. Exposing an image properly is perhaps the first step in photography. The exposure triangle parameters are the foundation pillars of photography. The three parameters are aperture, shutter speed and ISO. Whatever exposure changes you need to do in your camera will have to be done by adjusting these parameters only. Exposure triangle is nothing but a simple chart showing the stops of light of these three parameters on each side of the triangle. It is basically a cheat sheet for the beginners to learn the very basics of exposures. Before we dive deep into the exposure triangle, let us take a look at each of the parameters...

1)   The aperture:

The aperture is actually the opening of the lens. It is denoted by the ‘f’ number. The wider the opening of the lens the more light enters the camera sensor. The stops of aperture are as follows: f/1 -> f/1.4 -> f/2 -> f/2.8 -> f/4 -> f/5.6 -> f/8 -> f/11 -> f/16 -> f/22 and so on. The increase in number actually means that the aperture is narrowing down since it is an inverse fraction. Wide open apertures result in very shallow depth of fields. So the depth of field due to f/1 will be much shallower than the depth of field due to f/22. The amount of light entering the lens due to f/1 is much more than the amount of light entering due to f/22.

2)   The shutter speed:

The shutter speed is nothing but the speed at which the shutter of the camera operates. This is basically the time duration during which the camera shutter remains open to let the light in. The longer the duration the more the light. The stops of shutter speed are as follows:  1 second -> ½ second -> ¼ second -> 1/8 second -> 1/15 second -> 1/30 second -> 1/60 second -> 1/125 second -> 1/250 second -> 1/500 second -> 1/1000 second and so on. As you can see that the increase in number is actually lessening the duration. The amount of light that enters the camera when the shutter speed is 1 second is much more than the amount of light that enters the camera when the shutter speed is 1/500th of a second. Faster shutter speeds are used to freeze the action while slower shutter speeds are used to create motion blurs.

3) ISO:

This is an International Standard value to denote the sensitivity of the camera sensor to light. The stops of ISO are as follows: 100 -> 200 -> 400 -> 800 -> 1600 -> 3200 -> 6400 and so on. The increase in the numbers results in the increase in sensitivity of the sensor to light. An image taken with ISO 100 is going to be much darker than the image taken using ISO 6400 provided the other parameters remain same.

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Let us take a look at the exposure triangle. Everything in this world is measured by some units. Light in photography is measured by stops. The chart shows the stops of light of each of the three parameters. The left side of the triangle is the aperture side. As we travel upwards, the aperture narrows down which means the image gets darker. The right side of the triangle is the shutter speed side. As we travel downwards, the shutter speed increases which means that the image gets darker again. The base of the triangle is the ISO side. If we travel from right to left, the ISO value decreases which states that the image is getting darker. This entire flow is the basic of the exposure triangle.

Let us take a look at the following sets of exposure values and try to understand the difference in exposure in each

 f/2.8 ;; 1/500 sec ;; ISO 200:

In this setting if you feel you need to change the aperture to get a shallower depth of field, change the f number to f/2. To keep the overall exposure same, we need to adjust either the shutter speed or ISO. Change the shutter speed by a stop to 1/1000th of a second or change the ISO to 400 to get back the original exposure. Hence f/2.8 ;; 1/500 sec ;; ISO 200 is same as f/2 ;; 1/1000 sec ;; ISO 200 and f/2 ;; 1/500 sec ;; ISO 400. However 1 stop is not the minimum change. The minimum amount of change is actually 1/3rd of a stop of light. Between 1/500th of a second to 1/1000th of a second, there are fractional stops like 1/640th of a second (1/3rd stop) and 1/800th of a second (2/3rd stop). 

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The cheat sheet of exposure triangle parameters is the one which denotes the changes each parameter change brings to the table. In the above cheat sheet we can observe the following:

1)   The first row:

The aperture gets smaller from left to right. As a result the depth of field increases. The mountains are sharp on the right and blurred on the left. This shows the relationship between aperture opening and depth of field.

2)   The second row:

The shutter speed decreases from left to right. As a result the runner gets blurred on the right while it is in sharp focus on the left. This shows that fast shutter speeds freeze the action while slow shutter speeds result in motion blur.

3)   The third row:

The ISO increases from left to right. Although the brightness increases from left to right, the amount of digital noise increases too.

Exposure triangle parameter is the first pillar of photography. The stops of light should be inscribed on the back of your hand. You should be absolutely thorough with the concepts of exposure triangle parameters. This blog should help you achieve that and straightaway improve your photography significantly.

Basic Photography
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Pixean
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