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The Exposure Triangle Depicting all the Variables. Figs. 1 (Credit: WClark)

The Exposure triangle is a visual and theoretical understanding of the three main variables required to obtain an exposure. Shutter speed, Aperture and ISO each individually effect the final exposure. The correct balance of these variables produces a properly exposed image. It is very important that a photographer has a strong understanding of the exposure triangle as it is the base fundamental principal of the creation of every image. Understanding the exposure triangle allows the photographer to create a correctly exposed image

The exposure triangle is made up of three elements shutter speed, aperture and ISO. Aperture is the opening in the lens which controls the amount of light that comes through the lens. Aperture also controls the depth of field. Shutter speed controls the duration the sensor of the camera is open to light. ISO is the sensitivity of the camera’s sensor to light. The balance of these three variables allow the photographer to obtain the exposure they want.

Factors needed to understand:

Shutter Speed

Image depicting the same subject with different in shutter speed. Figs. 2.1 (Credit: User:Nevit)

Shutter Speed also called exposure time controls the duration the sensor is open to light. Like other variables shutter speed is measured in lengths of time each step shortens the length of time by a factor of 2. This halves the exposure making it darker.  Shutter speed controls many factors including sharpness. A higher shutter speed results in a freezing time while a longer shutter speed results in a blurry image. Shutter speed directly increases the exposure of the image as it allows the light to enter and produce an exposure. In figure 2.1 it shows the effects of shutter speed on the final image, the image on the left has a much shorter shutter speed in comparison to the image on the right. Figure 2.1 shows that with an increase in shutter speed the result is a blurrier image.

Aperture

Image showing the effect on depth of field with a smaller f number. Figs. 2.2 (Credit: )

Aperture is how open or closed the lens iris is. It works by opening and closing a whole which allows more or less light into the sensor. Aperture is measured in f numbers. A lower aperture, smaller f number will allow more light through as the opening is larger. While a lager f number will allow less light through as the opening is smaller. Aperture also effects depth of field as a smaller f number will result in a narrow depth of field while a larger f number will result in more to be in focus. Figure 2.2 shows the effects of a smaller aperture (smaller f number). It shows a small part of the image is in focus, this is a narrow depth of field.

ISO

Image showing the comparsion of images taken with diffrent ISO. Top portion is at ISO 100 and the bottom is at ISO 1600. Figs. 2.3 (Credit: User:HuttyMcphoo)

ISO is how sensitive the sensor of the camera is to light. As we increase ISO we can work with less light as the camera is more susceptible to light. As you increase the ISO it allows for photos in low light with acceptable shutter speed to avoid shutter shake. As you increase ISO you may also get some adverse side effects such as; lower quality and random background noise. Background noise also called grain produces an unpleasant effect in the image.   Figure 2.3 shows the effects of ISO, it shows that when using higher ISO we see the effects of noise.

Methodology

The exposure triangle is a combination of the three variables which allow the photographer to obtain the exposure they desire. A balance of all three values allows for a correctly exposed image. There are many different types of photography which need different settings to obtain the type of image the user would like. The us of these thee values produces an exposure value. This value usually only displayed from 23 to a -8 stops of light on most digital cameras. This value is a calculation made up of f number, shutter speed and ISO values to produce the final EV value. The EV value shows how close the photographer is to obtaining a correct exposure or how many stops of light they are over or under exposed by.

When a photographer decides to take a photo they will decide on the type of the image they would like. Once that decision is made they will pick one of the three variables they will need to use to obtain the image they would like. After that the photographer will then balance all three variables to allow them to obtain the image they would like.