The light triangle will help you understand the operation of your camera and the exposure’s logic, to create any picture you can imagine.

There are three basic parameters in any camera in the world; you can take control of, to achieving better results in your photos. By combining these parameters simultaneously, you will obtain several effects. Thanks to this knowledge, you will be able to reflect reality in a completely faithful way, or on the contrary, transform it completely.

Every photograph in the world relies on this three bases pillar. And the control of these variables can make a huge difference in your new pictures. We invite you to discover the secret behind each photograph you should always carry with you to succeed as a photographer.

The Three Vertices of Light Triangle

  • The ASA/ISO Value
  • The Diaphragm Opening
  • The Shutter Speed
Los tres vértices del triángulo de exposición

The Exposition

And The Light Triangle

Light is the basis for creating any photograph.

The final goal will always be to create an image with the correct exposure.

The photograph exposure can be: overexposed, well exposed or underexposed.

A photograph is correctly exposed when it is not underexposed-with very dark areas becoming to black-nor to be overexposed-with “burned” areas turning to white.

To obtain a correctly exposed image, you will have to combine the values of the three light triangle vertices so you will have: the adequate light amount, for the right time and with the appropriate sensitivity.

La Exposición y el triángulo de exposición

First Vertex Of The Light Triangle

The Sensitivity Of The Rolls Or Of The Digital Sensor · ASA/ISO Value ·

The ASA or ISO value is an international standard for all cameras in the world which indicates the light sensitivity of the digital sensor or of the photo roll.

With photos rolls for analog cameras, this value is fixed. The rolls range between ASA 100/1600; being the lowest number; the least sensitive to light and the highest number; the most sensitive to light.

Primer Vértice Del Triángulo de la Luz
La Sensibilidad de los Rollos ó del Sensor Digital
Valor ASA / ISO

In digital cameras, the sensor sensitivity is called ISO. It starts at the value 80 and reaches approximately 12800. The higher the number, the higher the sensitivity and therefore the image digital noise will also increase.

Primer Vértice Del Triángulo de la Luz
La Sensibilidad de los Rollos ó del Sensor Digital
Valor ASA / ISO

At lower ISO value, the sensor to light is less sensitive and vice versa; the higher the ISO value, the higher the sensitivity of the sensor. A low ISO value produces little or no digital noise. But as its value increases, the image begins to become granulated. You must ask yourself how much digital noise you are willing to accept for your photos’ final result.

If the ISO value increases, the grain in the image also increases, as we can observe in the following image.

La Sensibilidad del Sensor. El Primer Vértice del triángulo de exposición – Valor ASA / ISO

When a high ISO value is selected, the sensor can capture more light in a certain time. In digital cameras, this value is dynamic and can be modified with each shot, which will give you more versatility, because depending on the light amount available in the place, you can do more or less sensitive the sensor. In analog cameras, this value is only modifiable each time you change the photo roll.

Second Vertex Of The Light Triangle

The Diaphragm Opening

The diaphragm is the mechanical element inside each lens, which can be manipulated by modifying its aperture. It has a series of metal sheets moving to open or close it to the extent that we establish.

Segundo Vértice Del Triángulo de la Luz
La Apertura De Diafragma

With the diaphragm, we control exclusively the light amount we let through the lens and then reach the digital or negative sensor. This value is known as number “f”, and the jumps from one number to the next are called “steps” or “full stop.”

The larger the aperture-the smaller the number f-more light reaches the sensor.

The smaller the aperture-the higher the number f-the lesser light reaches the sensor.

La Apertura de Diafragma. El segundo Vértice del triángulo de exposición.

Each lens has a maximum and a minimum opening we can adjust. It varies slightly, but the lower diaphragm value is 1.7F, and the highest is 22F. A large aperture F4 allows more light to pass through the lens than a small aperture F16.

Opening the diaphragm as much as possible is a good option if we have a shortage of light. However, this does not only affect the light amount passing through the lens, but it also has another effect consequently: the shortening of the field depth; the sharpness area of an image. In some photographs, this far from being a problem can be an advantage.

Third Vertex Of The Light Triangle 
The Shutter Speed

The shutter is a device located in front of the digital sensor. It opens and closes every time you press the shutter button on your camera. It is responsible for controlling the time during which the sensor remains exposed to light.

La Velocidad De Obturación. El Tercer Vértice Del Triángulo de la Luz.

The shutter speed is measured in seconds or fractions of seconds: 1/1000, 1/500, 1/250, 1/125, 1/30, 1/8, 1/2, 1″, 2″, 5″.

The shutter speed simply controls the time length the shutter will remain raised to let light in; the longer the shutter stays open, more light reaches the sensor and vice-versa.

La Velocidad de Obturación. El tercer Vértice del triángulo de exposición.

Some cameras offer us a mechanism called Bulb: using which we can leave our shutter opens indefinitely to create images with long exposures.


Both expressions are referring to the same parameter although sometimes certain confusion can exist. By increasing the shutter speed the exposure time is reduced and vice versa; a fast shutter speed implies a short exposure time and a slow shutter speed a long exposure time.

Side Effects Of The Light Triangle

Each of the parameters of the Light Triangle, in addition to regulating the exposure, also modifies other image attributes. When these “side effects” is desired and enhanced, your new photographs will result in more creativity.

  • The Diaphragm Opening

In addition to modifying the light amount reaching the sensor, it also modifies the field depth, the distance between the closest point and the farthest point appearing neat regarding the main subject or object. Regulate how clear or out of focus the objects will appear in your image.

Efectos Secundarios del Triángulo de la Luz
  • The Shutter Speed

Besides modifying the light time it also modifies the elements movement appearing in the photograph. It can be about objects movements or subjects inside of the image or movement of the photographer’s hand. This may have artistic purposes or be a problem if we do not have a tripod.

Efectos Secundarios del Triángulo de la Luz
  • The ASA/ISO Value

In addition to modifying the light sensor sensitivity, it also generates noise in the image. Noise is the grain seeing in the images; the higher the ASA/ISO the greater the digital noise. This can also be artistic or be annoying. Increasing the ASA/ISO value is not something only done when the light levels are low, it can be used as a stylistic resource by intentionally generating desirable effects.

Efectos Secundarios del Triángulo de la Luz

Finally, the most important thing is to learn how to generate a balance between the three elements of the light triangle, to make a correct exposure. To achieve this, in conditions where light is scarce, you will need to sacrifice some of the side effects. It is a matter of practice. With the passage of time, the exposition technique will become part of the routine, and you will know how to adjust it easily.

If with this post you learned much more about photography than you already knew, surely you can be interested in other related subjects, such as the “dial modes of your camera,” or any different subject related to digital photography.

The light triangle is present in all the photographs. We could not leave you a gallery of photos on the light triangle because in that gallery would be all the photographs of the whole world. For that reason, in this opportunity, we have decided to share two videos to inspire you:



Be courageous and go out in search of your new photographs!


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