Triangles in Photography: Shutter Speed, ISO, & Aperture

Triangles in Photography depends on light; without it, there can be no photograph. The first step in learning photography is understanding the fundamentals, such as the exposure triangle and the terms used to describe it as well as how your camera operates.

Even though this step isn’t particularly exciting, skipping it would be a grave error in your quest to learn photography.

Triangles in Photography
Triangles in Photography

The best way to learn from your mistakes, adapt to all shooting scenarios, and, most importantly, control the light is to be familiar with your camera’s basic settings and know how to use them wisely.

By doing this, you will be able to exit automatic modes and move closer to getting the shots you desire.

How Does A Camera Work?

The first and most important step is to understand how your camera operates.

Don’t worry; I won’t get too technical and will keep it short and simple. Just keep in mind that there are three factors that can affect how light enters your device and is converted into an image. The light will enter the camera as soon as you press the shutter button:

The diaphragm of the objective: It is similar to the pupil of the eye. By increasing or decreasing its diameter, it adjusts the amount of light that passes through the lens.

The shutter: It’s like a little curtain that opens more or less wide to let in a certain amount of light.

The sensor: It is thanks to its photosensitive cells, called “photosites,” that the light will be transformed into an image.


Exposure is the amount of light that passes through the lens and impinges on the sensor, causing the brightness of an image to vary. Its value is expressed in IL (illumination index) or EV (exposure value). The term “STOP” is also used.

When an image lacks light, it is said to be underexposed. Conversely, an image that contains too much light, that is, is too white, is said to be overexposed.

Photo cameras offer a light measurement system called a light meter. You will find it at the bottom of your viewfinder or on your camera screen. It is symbolized by a ruler such as this:


The light meter interprets the amount of light that passes through the lens by taking into account the light reflected off the subject to be photographed.

This cursor tells you if your image is underexposed (cursor to the left of 0), correctly exposed (cursor in general, close, or on 0), or overexposed (cursor to the right of 0).

This measurement is only an indication; measurements may be inaccurate if there are too many dark or white tones in your scene. 

light meter interprets
light meter interprets

The Three Elements of the Exposure Triangle

As we saw above, you must take action on three factors in order to alter the amount of light entering your camera and subsequently correctly expose your photograph.

To ensure that your shot is properly exposed, you must also change the other two if you change one of them. Understanding the relationship between these three parameters is thus imperative.

Shutter speed :

Shutter speed Also called exposure time, it is expressed in fractions of a second (for example, 1/1000) or in seconds (for example, 3 s). This corresponds to the time during which the shutter will remain open to let the light pass.

The longer it stays open, the more light will hit your sensor, and vice versa. Please note that the speed is also affected by the movement of the subject. If you use too long an exposure time on a moving subject, it will blur.


ISO is the sensitivity of the sensor to light. It is used to artificially manage the perception of light by the sensor. For the same aperture and shutter speed, a higher ISO sensitivity will increase the exposure of the shot.

This can be interesting when the lighting conditions are low. But be careful, the more you increase the ISO to gain brightness, the more your camera will generate digital noise in return. It’s a real balance to find.

ISO sensitivity
ISO sensitivity

The Opening of the Diaphragm (Aperture)

The aperture is measured in f/, such as f/10. You have certainly already seen this inscription on the screen or in the viewfinder of your camera. This value is the diameter of the diaphragm. 

It changes the amount of light that passes through the lens, but it also impacts the depth of field, which is to say the area of sharpness in your photo.

Attention! There is a small trap in the inscription of this value; otherwise, it would lack spice. The higher the number following the f/, the smaller the diameter of the diaphragm, and conversely, the smaller the number, the more the diaphragm is open.

opening of the diaphragm
opening of the diaphragm

Here is how the exposure triangle is characterized:

The Exposure Triangle

Adapt to All Circumstances

Triangles in Photography

In landscape

When we take landscape photos, we generally try to have the greatest depth of field possible so that the sharpness of the photograph is at its maximum.

To do this, you will need to close your diaphragm. In landscape photography, an aperture between f/8 and f/11 is generally used.

You let less light through your lens by closing the diaphragm. To correct this, you will need to increase your exposure time or your ISO. By increasing your exposure time and passing a certain threshold, you risk, if you are shooting freehand, having motion blur.

If this happens to you, you will then have to increase the ISO because of the risk mentioned above, the “noise rise.” To avoid this, I advise you to use a tripod. 

This will allow you to be stable during your shot and therefore be able to use a slow shutter speed without having to increase the ISO.

In Portrait and Animal Photography

In these two situations, we try to freeze the subject’s movement. To prevent it from being blurry, you will need to use a fast shutter speed. To compensate for the loss of light, you will then have to open your diaphragm, which will reduce the depth of field

It’s a welcome effect because in portrait or animal photography, we try to detach the subject from the background. If after that you still don’t have enough speed to freeze the subject, you will have to mount the iso.

The Night

In night photography, two approaches are possible. In both cases, you will absolutely need to use a tripod to avoid camera shake and a very large aperture to capture as much light as possible.

    The first is to use a high enough ISO to minimize the exposure time. This will allow you to have no blur if there is a moving subject in the scene, with the risk that this entails in terms of noise.

    The second part consists of keeping the ISO fairly low, which will result in increasing the exposure time and avoiding too much noise.

    This technique can add quite dynamic effects to your photos, like streaks of clouds. However, as you will have understood, it is not suitable if you want to freeze a movement.


    At first, all of this might seem confusing, but the best way to learn these fundamentals is through practice. I encourage you to persevere because mastering the exposure triangle is necessary to succeed in photography.

    If you still have questions after reading this article, please post them in the comments section and I’ll be happy to respond.

    Bryan Silveira

    Bryan Silveira

    Photography is a powerful medium for capturing and preserving memories, telling stories, and expressing one's creativity. The art of photography offers endless possibilities for exploring your creativity and expressing yourse