The Exposure Triangle is one of the fundamentals of photography, it is about three things - aperture, shutter speed and ISO. These are the three variables that determine the exposure of a photograph. There must be a balance between all three of these elements to achieve an accurately exposed image. If one of these settings is changed without adjusting at least one of the others, then this will undoubtedly effect the image, usually in terms of either brightness, colour range/quality or depth of field.
The aperture controls the amount of light coming into the lens. Similar to the human eye, the camera lens has a mechanical component, similar to an iris, that shifts in size to allow more or less light into the lens. The aperture will influence two aspects of your photograph; the shutter speed and depth of field. For macrophotography or portraiture, a wide aperture is preferable, which is a low f-stop such as f/1.4 to f/2.8. A low aperture is generally used to create shallow depth of field to isolate the subject and make it pop. You might notice this in images that have a sharp subject against a blurred background (known as “bokeh”). For landscape photography a narrow aperture, which is a high f-stop such as f/11 to f/16, is desirable for greater depth of field to get as much of the image sharp and in focus as possible.
Shutter speed is the length of time that the camera shutter remains open to let light hit the sensor in the body of the camera. Similarly to aperture, your shutter speed can be influenced by the style of photography you are shooting or your subject. To freeze action a fast shutter is preferable but to emphasis movement a slow shutter speed can be used. Shutter speeds are generally measured in fractions so 1/2 is half a second, while 1/50 is one fiftieth. On most SLR cameras these figures will not be displayed as a fraction, 1/2 will appear as 2 and 1/50 will simply be 50 on your camera display. If you use shutter speeds longer than one second they will display as 1” or 5” which translates to 1 second or 5 seconds.
ISO is the light sensitivity of your camera’s sensor. A higher ISO makes the camera sensor more sensitive to light and a lower ISO makes it less sensitive. Most SLR cameras have the ability to select ISO settings between 100 and 12,800, with a number of predefined increments or what are referred to as “stops” contained within that range. Increasing the ISO allows you to shoot in low light conditions, however, this can come at the expense of the quality of your final image. While it varies between camera models, generally a higher ISO translates to an image with more noise or grain and reduces the quality and colour range captured in the shot. Considering colour and detail are important components of landscape photography it is preferable to keep ISO settings as low as possible depending on the shooting conditions.
So in essence, the idea behind using the Exposure Triangle as a model is to reinforce the importance of keeping the three sides of the triangle - aperture, shutter speed and ISO - in balance with each other. If you increase one of these three settings then you will have to alter one or both of the other settings to maintain that balance. The best way to be able to achieve this is by using Manual Mode (M) on your camera as this gives total control and flexibility. Knowing the exposure triangle is fundamental to taking great images, while it may seem a little confusing at first, it is something that does become intuitive over time.
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