Photography Exposure Triangle


As we all know… Light is the key to photography. The Exposure Triangle is how we control the available light for an image. The elements are ISO, aperture, and shutter speed. These settings are adjusted to get the image to look the way you want.


ISO is the numerical exposure index of a photographic film under the system adopted by the International Standardization Organization, used to indicate the light sensitivity of the film's emulsion (Formally known as ASA, American Standards Association). In the Digital Photography Era, ISO is the measurement of how sensitive the camera's image sensor is.

Shutter Speed

Now shutter speed… There is a shutter in front of the sensor that opens and closes, when the shutter release button is pressed. The duration of the shutter opening is the shutter speed. This is the amount of time that the sensor is exposed to light. I like to think of shutter speed as one of the creative controls on my camera. You can creatively freeze action or blur action.


Aperture is the opening in the lens that allows light into the camera and to the sensor. You adjust the aperture to determine the amount of light to allow in. I also think of aperture as a creative control. The wider the aperture is opened, the shallower depth of field in your image. The smaller your aperture, the more depth of field.

The Sink!

The Sink!

Here's a very creative explanation of the triangle. This is how it was explained to me. Okay... Think of a faucet. The spicket is the shutter speed. The opening of the faucet is the aperture. The sink area with little tiny workers represent the ISO. So, you turn the spicket (I wonder does everyone know what a spicket is) to start the water. The opening of the faucet is set. Let's say the faucet (aperture) is wide open. For the duration of the spicket being turned (shutter speed), water (light) enters the sink (sensor). The workers (ISO) paint the image. But because of the wide opening, the workers only have time to paint the important parts of the image (the part of the image that is focused on). This leaves the rest of the image blurred or out of focus. If the faucet opening (aperture) was small, the workers (ISO) would have an easier time painting the whole frame (sink). I hope this makes sense. It was easier for me to see it this way.

The Sink!

Do you have a creative way to explain exposure? Do you shoot in Aperture Priority mode or Shutter Priority mode from time to time?