Exposure Triangle Simplified

Exposure Triangle is a way of visualizing the relationship between the three primary controls of a camera that controls the amount of light reaching the sensor. The three primary controls are Aperture, Shutter Speed and ISO, the only controls we need to master to make a jump from Auto to Manual. Not saying, other controls are not important, it’s just that we can park those aside for now, at least when we are just getting started in Photography. Here is a blog “Exposure Triangle Simplified” to help simplify the concept for you.

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1. What is Exposure in Photography?

Exposure in simple words refers to how bright or dark an image is in Photography. It’s a delicate balance all photographers strive to achieve. A photograph can be Underexposed, Overexposed or properly exposed.

Exposure is an interplay of the three primary controls of a Camera: Aperture, Shutter Speed and ISO, which eventually controls the amount of light hitting the sensor. It is a fundamental concept that helps us visualize the interconnectedness of these three primary controls in exposing a photograph.

2. What are the three primary controls controlling the Exposure in Photography?

The three primary controls are:

1. Aperture – It is the opening in the lens, controlling the amount of light that passes through the lens opening. The larger the opening, the larger is the amount of light passing through the lens and vice-versa.
2. Shutter Speed – It is the duration for which the camera shutter remains open. It controls how long the light is allowed to pass through. The longer the duration, the longer the light is allowed to pass through the lens opening to the sensor and vice-versa.
3. ISO – ISO in simple words, in a digital world, is a brightness control right inside the camera. A high ISO would increase the brightness, whereas a low ISO would do the opposite. ISO is usually related to the sensor, for now, let’s just say ISO is sensitivity to the light in an image. We will cover this topic in detail in another blog.

3. Exposure Analogy

A good photo needs to have a balanced exposure, and a balanced Exposure calls for balancing the three primary controls of the camera:

1. Aperture
2. Shutter Speed
3. ISO

Just like when we bake a cake, we need to balance:

• The oven temperature (Aperture): It relates to the cooking rate. Imagine there’s an imaginary door in the oven that controls the amount of heat entering. This is similar to the aperture in a camera lens, which controls the amount of light entering. A wider “door” (larger aperture) allows more heat (light) in, cooking the cake faster, while a narrower “door” (smaller aperture) lets in less heat (light), taking longer to cook.
• The baking time (Shutter speed) – It relates to the control of overall duration of baking the cake at the selected temperature, similar to the duration for which the light entering through the lens opening is allowed to reach the sensor.
• The cake ingredients (ISO) – It relates to ingredients’ sensitivity to the overall taste, just like increasing or decreasing the sensitivity of the sensor to the light, in turn, making the image brighter or darker depending on the case.

We misjudge one element, the impact of other elements on the cake also either increases or decreases. A perfect cake requires a harmonious balance of these factors. Similarly, for a well exposed photo, the 3 primary elements Aperture, Shutter Speed and ISO, controlling the amount of light hitting the sensor, are interrelated. If one element is off, it can significantly impact the outcome, either overexposing or underexposing the image.

4. Exposure Triangle Simplified

Now, since, we have some basic idea of what exposure is and the three primary controls of the camera, let’s dive in deep to understand how the interconnectedness of these controls play out when we click a photo. But before we have a look at the Triangle, let us understand how each of these three controls impact the scene in an image when the respective values are changed:

4.1 Aperture

We have learned, Aperture is the opening in a lens which controls the amount of light reaching the sensor. When we rotate the Aperture dial, it either broadens or narrows the lens opening, depending on the selection made. Let me list the key points that we must understand and remember about Aperture:

• The Aperture values on your camera will look like f/1.4, f/2.0, f/4.0, f/5.6, f/8.0, f/11.0, etc. reaching all the way up to f/22.0.
• These are f-stops or f-numbers, a measure of the size of the opening of a lens.
• Remember, larger the number, narrower the opening and smaller the number, wider the opening.
• It controls the Depth of Field (DOF) in a scene.

a. What is Depth of Field (DOF)?

Depth of Field (DOF) is a simple concept: it’s the range of distances in a scene that appear acceptably sharp in a photo.

Imagine you’re taking a picture of a line of ten objects. Depending on how you set up your camera (aperture, focal length, and subject distance), some of those objects will be sharp, while others will be blurry. This range of sharp focus is the Depth of Field.

b. What are the Key Factors Affecting DOF?

Aperture: A wider aperture (lower f-number like f/1.8) creates a shallower DOF, with only a few objects in focus. A narrower aperture (higher f-number like f/16) creates a deeper DOF, with more objects in focus.

Focal Length: Longer focal lengths (telephoto lenses) tend to produce shallower DOF, while shorter focal lengths (wide-angle lenses) tend to produce deeper DOF.
Subject Distance: The closer your subject is to the camera, the shallower the DOF will be.
By understanding these factors, you can control the amount of the scene that’s in focus, allowing you to create images with the desired level of sharpness and blur.

Spend some time analyzing the images below. Determine which photograph indicates the use of a wide aperture and which photograph suggests a narrower aperture.

CLICK TO EXPAND

c. What is Shallow DOF?

A Shallow DOF means only a little area of the scene in a photograph is in sharp focus.
Visual Effect: A shallow DOF creates a dreamy background blur effect in a Photograph, also known as Bokeh effect. This helps the subject standout in the image by separating the subject from the background.

d. How to achieve shallow DOF?

To achieve shallow DOF, a wide aperture, a long focal length and placement of subject closer to the camera is essential.

• Aperture: A wide Aperture i.e. an aperture with a low f value.
• Focal Length: The longer the focal length of the lens (Telephoto) shallower the DOF.
• Subject Distance: The closer the subject is to the camera, the shallower the DOF. Additionally, worth noting, farther the subject is placed from the background, again the subject separation from the background will be further enhanced.

e. When to use shallow DOF?

Shallow DOF can be used in those types of Photography which requires a blurred background and a sharp subject. Example, Portrait Photography, Macro Photography, Product Photography, etc.

f. What is Deep DOF?

A Deep DOF means a large area of the scene in a photograph is in sharp focus. A deep DOF will have the foreground as well as background in focus.

g. How to achieve deep DOF?

To achieve a deep DOF, a narrow aperture, a short focal length and placement of subject farther to the camera is essential.

• Aperture: A narrow Aperture i.e. an aperture with a large f value.
• Focal Length: The shorter the focal length of the lens, deeper the DOF.
• Subject Distance: The farther the subject is to the camera, the deeper the DOF.

4.2 Shutter Speed

Shutter speed is like a camera’s eyelid. It controls how long the sensor, which is like the camera’s eye, stays open.

• Slow Shutter Speed: When the shutter stays open for a long time, it’s like keeping your eye open for a long time in a dark room. More light enters, making the photo brighter. However, moving objects appear blurry.
• Fast Shutter Speed: When the shutter opens and closes quickly, it’s like blinking really fast. Less light enters, making the photo darker. But moving objects appear sharp and frozen in time.

Shutter speed is measured in fractions of a second, like 1/15, 1/30, or 1/60. Smaller numbers mean a slower shutter speed, and larger numbers mean a faster shutter speed. Can you visualize the reason for such shutter speed in the images below? Share your thought process in comments.

4.3 ISO

ISO in a camera (specifically a film camera) can be likened to an amplifier for light.

• Film Sensitivity: In film photography, ISO directly correlates with the film’s sensitivity to light. Higher ISO film is more sensitive to light, allowing for shorter exposure times in low-light conditions.

• Light Amplification: Imagine ISO as an amplifier boosting the strength of the light signal that reaches the film. This increased sensitivity allows the film to record an image even with limited available light.

• Digital Cameras: While the concept of ISO originates from film photography, its implementation in digital cameras is slightly different. In digital cameras, ISO primarily controls the gain of the electrical signals generated by the image sensor. Higher ISO settings amplify these signals, enabling image capture in low-light situations.

a. Higher ISO:

• More Sensitive:

  A high ISO setting allows you to capture images in low-light conditions by increasing the camera’s sensitivity to light.

  • Film Photography: In film cameras, higher ISO film is more sensitive to light, allowing it to record an image with less exposure time.

  • Digital Photography: In digital cameras, a high ISO setting increases the gain of the analog signal. This amplifies the electrical signals recorded at the sensor, effectively making it more sensitive to light.

  This increased sensitivity enables you to capture images in low-light situations with faster shutter speeds or smaller apertures, which would otherwise result in an underexposed image.”

• More Noise: This increased sensitivity/ gain can lead to noise or grain in the image, especially at very high ISO settings, however, conditions applied. Stay tuned for an advanced photography blog on the topic.

b. Lower ISO:

• Less Sensitive: The film is less sensitive to light, whereas a digital sensor has less gain, resulting in cleaner images.
• Need for More Light: This often requires more light, either from a brighter scene or additional light sources.

Spend a few moments analyzing the images below. Try to understand why the specific ISO for each shot. Share what you think in comments.

In essence, ISO balances the need for light with image quality. A higher ISO allows you to capture images in darker environments, but it comes at the cost of potential noise. A lower ISO produces cleaner images, but you may need more light to achieve proper exposure.

5. How Exposure Triangle work?

Now that we’ve discussed aperture, shutter speed, and ISO individually, let’s explore how they work together in a concept known as the Exposure Triangle.

Imagine you’ve dialed in the perfect exposure for a scene. But what if you want to make a creative adjustment? For example, if you want to blur the background and focus on your subject, you’d open the aperture wider (let’s say, by two stops).

To maintain the same exposure, you’ll need to compensate for the increased light entering the camera. You can do this by either:

Increasing the shutter speed: This reduces the amount of time the sensor is exposed to light.
Decreasing the ISO: This lowers the sensor’s sensitivity to light.
However, increasing the shutter speed too much can lead to motion blur, especially in low-light conditions or when photographing moving subjects. Decreasing the ISO, on the other hand, can produce a cleaner image with less noise.

The choice between adjusting shutter speed or ISO depends on your specific photographic goals. By understanding the exposure triangle and how these three elements interact, you can create stunning images in a variety of lighting conditions.

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If you found this blog (Exposure Triangle Simplified) helpful, here are few other blogs to get you some practical tips on Photography:

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Don’t hesitate to connect with me at my Insta handle @pankajsinghphotographie