The exposure triangle
The exposure triangle is a simple illustration allowing to understand how exposure is controlled.
So before defining the exposure triangle, Let's start by understanding exposure.
Exposure defines how light or dark each element of your photograph will be. There is no absolute unit of measure of exposure, but there is a relative measure, which is the f-stop. By relative measure, I mean that you can compare two exposures of the same subject in terms of f-stops.
Think of it this way. The same object can appear in a photograph as being very dark, very light or midtoned. What you should know is that, in the photographic spectrum, the difference between very dark and very light is 5 f-stops.
These images illustrate the concept of exposure:
So before defining the exposure triangle, Let's start by understanding exposure.
Exposure defines how light or dark each element of your photograph will be. There is no absolute unit of measure of exposure, but there is a relative measure, which is the f-stop. By relative measure, I mean that you can compare two exposures of the same subject in terms of f-stops.
Think of it this way. The same object can appear in a photograph as being very dark, very light or midtoned. What you should know is that, in the photographic spectrum, the difference between very dark and very light is 5 f-stops.
These images illustrate the concept of exposure:
The exposure triangle - understanding exposure
Now how can you control exposure?
The factors controlling exposure can be summarized in a simple diagram called the exposure triangle.
The factors controlling exposure can be summarized in a simple diagram called the exposure triangle.
The exposure triangle
In the exposure triangle shown here, the three red triangles result in the same exposure, while the yellow one is overexposed vs. the red ones by three stops.
Going through the exposure triangle, we can see three ways to control exposure:
o aperture and exposure: the aperture is the diameter of the opening of the diaphragm through which the light enters and reaches the sensor (or film). Aperture is measured in ratios of focal length. For example, an aperture of f/16 (usually called simply 16) with a focal length of 100mm means that the diameter of the hole is 100/16=6,25mm.
o shutter speed and exposure: The shutter speed, measured in seconds or fractions of a second, is the time during which the diaphragm remains open, allowing light to get to the sensor (or film). The longer the shutter speed, the more light on the sensor (or film).
o sensitivity and exposure: Sensor or film sensitivity is measured in ISO and defines how the sensor or film reacts to a certain quantity of light. The higher the ISO, the higher the sensitivity to light.
The first two levers allow to control the amount of light reaching the film or sensor, while the last one defines the reaction of the film or sensor to a certain amount of light.
All these concepts can be summarized in the exposure triangle. If you are planning to start using manual exposure, or even semi-automatic, you need to develop a good understanding of the exposure triangle concept. This is one of the basic concepts you need to know about photography, and that you will find in all photography 101 classes.
For more info on the exposure triangle, you can view this excellent video by Mark Wallace.
o aperture and exposure: the aperture is the diameter of the opening of the diaphragm through which the light enters and reaches the sensor (or film). Aperture is measured in ratios of focal length. For example, an aperture of f/16 (usually called simply 16) with a focal length of 100mm means that the diameter of the hole is 100/16=6,25mm.
o shutter speed and exposure: The shutter speed, measured in seconds or fractions of a second, is the time during which the diaphragm remains open, allowing light to get to the sensor (or film). The longer the shutter speed, the more light on the sensor (or film).
o sensitivity and exposure: Sensor or film sensitivity is measured in ISO and defines how the sensor or film reacts to a certain quantity of light. The higher the ISO, the higher the sensitivity to light.
The first two levers allow to control the amount of light reaching the film or sensor, while the last one defines the reaction of the film or sensor to a certain amount of light.
All these concepts can be summarized in the exposure triangle. If you are planning to start using manual exposure, or even semi-automatic, you need to develop a good understanding of the exposure triangle concept. This is one of the basic concepts you need to know about photography, and that you will find in all photography 101 classes.
For more info on the exposure triangle, you can view this excellent video by Mark Wallace.
