The exposure triangle for beginners

How can you leave automatic mode and finally learn your camera settings? In this article, you will learn how to:

• Understand aperture, shutter speed and ISO without technical jargon
• Use manual mode in photography
• Master your camera in the field

Like you, after spending several hundred euros on a camera, I had to learn how to use it.

A few technical basics are enough to transform your images, even if they are not the only thing that matters!

Why leave automatic mode?

Let’s talk a little about automatic mode. The camera takes an exposure reading (see the next chapter) and then “adjusts” these settings to produce a properly exposed image.

However, you have probably already experienced getting blurry photos in low light conditions. Or perhaps you have felt that your subject was lost in its background.

You will understand the purpose of each setting, what it changes in your final image, and I will even share the exercises I used to become familiar with my camera.

You will finally understand how to isolate a subject from its background or even create dreamy atmospheres by smoothing the movement of a waterfall.

Exposure metering

Before talking about technique, it is important to understand what a camera actually does: capture light on film or, more recently, on a sensor. Today, cameras are mostly digital, so I will focus on those in this article. The principle remains the same:

• Your sensor (or film) starts in complete darkness (at this stage the final image is black)
• It is then exposed to light, and the image gradually becomes brighter (until it eventually turns white)

I use this comparison from black to white because it helped me greatly understand exposure. The more your sensor is exposed to light, the brighter or “whiter” the final result will be. This is true regardless of the scene you are photographing (landscape, portrait, etc.).

But before discussing special cases such as images that are too dark or too bright, let’s look at the general case: proper exposure.

Cameras continuously perform a measurement called exposure metering. It has no direct impact on your final image; it is simply information provided by your camera.

This measurement does not directly affect your image. It simply tells you whether your settings will produce a properly exposed photograph.

In automatic mode, we are often unaware of this measurement, but it becomes very useful when we want to achieve a specific result, such as keeping a subject sharp while creating a blurry background.

We will now see how to manually adjust these settings to achieve proper exposure and, more importantly, understand their impact on the final image.

Understanding the exposure triangle simply

To properly expose an image, the camera must allow a certain amount of light to reach the sensor. We can adjust three settings, all linked to one another:

• Aperture
• Shutter speed
• ISO sensitivity

The relationship between these three settings is called the exposure triangle.

If you change one of them, you will need to compensate with one of the other two.

Let’s imagine a simple scene: you are photographing a landscape in manual mode (you control every setting yourself) and your exposure meter is centered. If you open the aperture wider, more light reaches the sensor. You will therefore need to compensate either with shutter speed or ISO to return to a balanced exposure.

There are therefore many possible combinations of settings that can produce the same exposure, but the final results may look very different. This concept may seem complex at first, but with practice and exercises, it will become much easier to understand.

Aperture: choosing what stays in focus

Aperture and its effect on exposure

Aperture refers to the opening inside your lens. Blades inside the lens allow more or less light to enter. When they are closed, less light reaches the sensor. When they are opened, more light enters.

If this setting is not properly controlled and the aperture is too closed, your image will be dark because not enough light reaches the sensor. Conversely, if the aperture is too open, your image may become completely white.

Except for specialized equipment, aperture follows a standardized scale where each step lets in either twice as much or half as much light. A larger f number means the blades are more closed, while a smaller f number means they are more open.

There is a physical limit to how far your lens can open or close, and these limits are indicated on the lens itself.

Aperture and its effect on the image

But how does aperture affect your photograph?

Besides its effect on exposure, there is another concept to consider that I will not cover in detail in this article: depth of field. This is the area of your image that appears sharp. Anything in front of or behind that area will appear blurry.

Aperture directly influences depth of field. Closing the aperture increases depth of field.

Here are some practical examples:

• The more you close the aperture, the greater the depth of field becomes (useful for landscape photography, for example)
• The more you open the aperture, the shallower the depth of field becomes, allowing you to create a blurry background (very useful for separating a subject from its background, such as in portrait photography)

However, as we saw above, if you close the aperture too much, less light reaches the sensor, so you will need to compensate using the other two settings.

Conclusion on aperture

• The lower the number (for example f/2.8), the more light reaches the sensor, but the shallower the depth of field becomes.
• The higher the number (for example f/22), the less light reaches the sensor, but the greater the depth of field becomes.

Shutter speed: freezing or smoothing motion

Shutter speed and its effect on exposure

The second setting is shutter speed. Imagine a door in front of your sensor. When you press the shutter button to take a photo, this door opens so that light can reach the sensor and then closes again. Shutter speed corresponds to the amount of time the sensor is exposed to light.

The higher the shutter speed, the faster the door opens and closes, meaning the sensor is exposed for a shorter period of time.

As with aperture, a shutter speed that is too fast can result in a dark image, while a slow shutter speed can produce an image that is too bright.

Shutter speed and its effect on the image

Shutter speed directly affects how motion appears in your photograph.

A fast shutter speed freezes movement.

For a slow shutter speed, let’s take an extreme example: a shutter speed of 10 seconds. The shutter opens and the sensor is exposed to light for 10 seconds. If your subject moves during that time, it will appear blurred in the final image.

Conclusion on shutter speed

• The slower the shutter speed, the longer the sensor is exposed to light.
• The slower the shutter speed, the more movement will appear smooth or blurred.

ISO: light… and noise

ISO and its effect on exposure

ISO refers to your sensor’s sensitivity to light.

Your aperture and shutter speed are fixed and allow a certain amount of light to reach the sensor. The higher the ISO value, the brighter your image will appear.

Let’s take a common situation in nature photography. Imagine you are in a dark environment. Your subject is moving slightly, so you need a relatively fast shutter speed. The scene then becomes too dark, so you open the aperture. If the image is still too dark, you can increase the ISO and obtain a properly exposed photograph.

In most situations, ISO is the last setting photographers adjust because of its impact on image quality.

ISO and its effect on the image

You may have already heard of “digital noise”. This is the main consequence of using high ISO values. Digital noise often appears as colored grain in the darker areas of an image.

Every photographer has a different tolerance for noise. I recommend performing tests like the ones shown below to determine at which ISO level the result becomes unacceptable for you.

Conclusion on ISO

• In challenging lighting conditions, if shutter speed and aperture do not allow you to achieve proper exposure, you can increase the ISO.
• Be careful: if the ISO value becomes too high, digital noise will appear in the darker areas of the image.

The best way to learn: aperture priority and shutter priority modes

To gradually move away from automatic mode, the A (or Av) and S (or Tv) modes on your camera are excellent tools before switching to manual mode. Here is a brief description of these modes:

• A mode (or Av): aperture priority mode. The photographer selects the aperture, while the camera automatically adjusts shutter speed and ISO (although ISO can remain fixed if desired).
• S mode (or Tv): shutter priority mode. The photographer selects the shutter speed, while the camera automatically adjusts aperture and ISO (although ISO can remain fixed if desired).
• M mode: manual mode. This mode should be used once you feel comfortable with the three settings. Here, the photographer controls everything.

Aperture priority and shutter priority modes are particularly useful when starting out because they help you understand how each setting affects the final image.

The exercises that helped me improve

These are the exercises that genuinely helped me understand the exposure triangle.

The subject itself does not matter, nor does whether you are indoors or outdoors. However, I recommend working in good light conditions to avoid ending up with too many dark images.

Aperture exercise

For this exercise, set your camera to A mode (aperture priority). Place a stationary subject in front of your camera at a fixed distance and try to have a background that is well separated from the subject. If the background is too close, it will be difficult to notice the effect of the aperture.

Take a series of photographs using every aperture available on your lens, from the widest aperture to the narrowest (or vice versa).

When comparing your results, you should notice that aperture can either blur the background or make it more visible.

Shutter speed exercise

For shutter speed, I am fortunate enough to live by the sea, but a simple clock or any other moving subject will work just as well. To make the exercise more meaningful, your subject should ideally move at a constant speed.

For this exercise even more than the previous one, I recommend placing your camera on a tripod or at least on a stable surface.

As I explained earlier, a slow shutter speed smooths movement. However, you should be aware that the photographer also introduces movement through small vibrations, even when simply pressing the shutter button. Your camera therefore needs to remain completely still for this exercise.

Set your camera to S mode (shutter priority) and select a fast shutter speed. Gradually decrease the shutter speed, taking a photo at each setting.

When comparing your images, you should notice that movement becomes increasingly smooth, or in other words, that the moving subject becomes progressively blurrier.

ISO exercise

For this exercise, your image should contain a dark area.

Set your camera to M mode (manual). Set the ISO to its lowest value, then adjust shutter speed and aperture until the exposure meter is centered.

Take one photo for each ISO value, but remember to compensate using shutter speed and/or aperture to maintain the same exposure.

When comparing the images, you should notice digital noise becoming more visible as the ISO value increases.

Exposure compensation

Now that you are familiar with A, S and M modes, it is useful to understand exposure compensation.

When performing your tests in A or S mode, the camera automatically calculated the settings required to achieve a centered exposure.

However, if you intentionally want a brighter or darker image, you can simply apply positive exposure compensation (brighter image) or negative exposure compensation (darker image).

FAQ

Should I always use manual mode to improve in photography?

No. It depends on the situation. Use the mode that best suits your needs.

Personally, I photograph almost everything in aperture priority mode while keeping an eye on shutter speed and ISO values.

Why are my photos too dark?

If you are using A or S mode, the problem may come from your exposure compensation setting. Make sure it is set to 0 if you want a neutral exposure.

If you are shooting in manual mode, you will need to adjust your settings. Use the exposure meter to help ensure proper exposure.

What is the difference between A mode and S mode?

A mode is aperture priority mode. In this mode, the photographer controls only the aperture. The camera automatically adjusts shutter speed and ISO.

S mode is shutter priority mode. In this mode, the photographer controls only shutter speed. The camera automatically adjusts aperture and ISO.

How can I lock ISO in A or S mode?

Most cameras allow you to either fix the ISO value or define a maximum ISO limit.

Look in your camera menu for options such as “ISO settings”, “Auto ISO control”, or “Maximum ISO”. These settings allow the camera to adjust exposure more precisely while staying within the limits you choose.