Exposure Triangle

Preston Andrew Schlund

Exposure Triangle

The exposure triangle is a common way of associating the three variables that determine the exposure of a photograph: aperture, shutter speed, and ISO. One must balance all three of these to achieve a desired result.
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Shutter Speed

  • In photography, shutter speed or exposure time is the length of time when the film or digital sensor inside the camera is exposed to light, also when a camera's shutter is open when taking a photograph. The amount of light that reaches the film or image sensor is proportional to the exposure time
  • Whenever a scene contains moving subjects, the choice of shutter speed therefore determines which of these will appear frozen and which will be recorded in a blur
  • You can use slow shutter speed to use blur to focus on a certain object in a image
  • Anything that moves on the scene of a slow shutter speed will blur
  • A fast shutter speed could be considered anything over 1/500th of a second.
  • One of the most common is to freeze movement in sport. Pro sports photographers use fast shutter speeds to capture the action.

Aperture

  • A device that controls the amount of light admitted through an opening. In photography and digital photography, aperture is the unit of measurement that defines the size of the opening in the lens that can be adjusted to control the amount of light reaching the film or digital sensor.
  • Without a doubt, it is the most talked about subject, because aperture either adds a dimension to a photograph by blurring the background, or magically brings everything in focus.
  • A smaller f-stop means a larger aperture, while a larger f-stop means a smaller aperture. Most people find this awkward, since we are used to having larger numbers represent larger values, but not in this case. For example, f/1.4 is larger than f/2.0 and much larger than f/8.0.
  • One important thing to remember here, the size of the aperture has a direct impact on the depth of field, which is the area of the image that appears sharp. A large f-number such as f/32, will bring all foreground and background objects in focus, while a small f-number such as f/1.4 will isolate the foreground from the background by making the foreground objects sharp and the background blurry

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ISO

  • One of the three components of exposure of photographs is the sensitivity of your image sensor or film inside your camera. This measure of sensitivity is expressed as ISO speed – and it's kind of a big deal when your light is less than ideal.
  • Higher ISO settings are generally used in darker situations to get faster shutter speeds.
  • For example an indoor sports event when you want to freeze the action in lower light. However the higher the ISO you choose the grainier your shots get.
  • If there is plenty of light, I want little grain, I’m using a tripod and my subject is stationary I will generally use a pretty low ISO rating.
  • Concerts – also low in light and often ‘no-flash’ zones
  • Art Galleries, Churches etc- many galleries have rules against using a flash and of course being indoors are not well lit.
  • Birthday Parties – blowing out the candles in a dark room can give you a nice moody shot which would be ruined by a bright flash. Increasing the ISO can help capture the scene
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