Monday, 7 May 2018

Blog on Exposure Triangle

Photography is defined as drawing with light with the help of a light tight box called camera. To click a picture we need to provide a sufficient light to the camera so that it can identify the subject to be clicked.

To get that amount of light the camera needs to click a good picture we should understand the concept of exposure triangle, because the overexposed and underexposed images are not considered good images. 


Exposure triangle is the combination of aperture, shutter speed and ISO. We must balance these three variables to get a perfectly exposed picture. These three components are parts of camera which depends on each other. So an adjustment in one will require adjustment in others.

   Correctly exposed


Aperture is the hole in the lens through which light enters into the camera.  Size of this hole can be increased or decreased as per the lighting conditions. A wide aperture means more light will enter into the camera while a narrow aperture will allow less light. 

Aperture is denoted by f number which is universal. The usual numerical values for the f-stop are 1.4, 1.8, 2.0., 2.8, 3.6, 4, 5.6, 8, 11, 16 and 22. If we are shooting in low light conditions we need to lower down the f number to 2.0 or 1.8 while for situations where we have more light we need to increase the f number to 16 or 22.

Shutter speed

Shutter speed decides the time for which shutter remains open and thus for how the sensor is exposed to light. Faster shutter speed means less time while slow shutter speed means more time for which light is inside the camera.

Shutter speed is measured in seconds or fraction of seconds like ½, 1/4, 1/100s, 1/250 and so on. 1/100s, shutter speed means that shutter will open for one hundredth part of a second while 1/1000 shutter speed means that shutter will open for one thousandth part of a second. We keep high shutter speeds when we want to freeze the action or capture the motion.


ISO is the sensitivity of the film in case of film camera while image sensor in digital camera. It means how sensitive your film or image sensor is towards light. High sensitive image sensor needs less amount of light to get exposed or click the image while less sensitive image sensor needs more light to get exposed.

ISO value is measured in numbers. Lower the number, the lower the sensitivity to light. Higher values mean it is more sensitive to light. Depending on the camera, the lowest value stars from 50 can go up to 6400. Photographers who want more saturation and less noise and more details in the picture should go for ISO 100 or 200.

Thus by combining the ISO, aperture and shutter speed gives a correct exposure value for a particular setting. One thing you have to keep in mind is that if any one of the elements is changed or adjusted then we also need to change the other two to get the correct exposure otherwise your image would be too bright or too dark or noisy.

Ms. Sanyogita Choudhary
Assistant Professor
Department of Communication studies

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