Three basic concepts of photography relate together to properly exposed a photograph, hence the term triangle, the three basic elements are the ISO, shutter speed and the aperture of a camera. The aim of this article is to explain in the simplest way how ISO, shutter speed and aperture work hand in hand to produce the perfect exposure for an image. Before we talk about exposure, let us look at these three basic photography element and understand them.
Before we talk about ISO, shutter speed and aperture, let us understand the term “stop”. The halving or doubling of the amount of light responsible for the exposure of an image is what is termed as a stop. If a picture is underexposed, you add a stop of light which then doubles up the exposure and the image is brightened, also, halving the amount of light will darken an image that is overexposed.
The aperture is a small opening in the lens that only opens up when the camera is fired to allow light reach the image sensor. When the opening of the aperture is doubled, the exposure on the image is increased by a stop and when halved, the exposure is decreased by a stop and less light hits the sensors.
The ISO deals with the level of sensitivity of your camera to the amount of light available. With an increased sensitivity, your camera performs better in low light conditions, so at a very high ISO value, your sensors do not need much light to have good exposure but low ISO value means there is a need for a greater amount of light to create a correct exposure.
The shutter speed is the length of time the camera shutter stays opens to allow light hit the image sensors. So at the shorter shutter speed, a lesser amount of light hit the sensors and we have decreased exposure but when the shutter speed is increased from say ¼ seconds to 1 second, we have increased the exposure by two stops.
This three have to combine perfectly for have the right exposure for an image, there is no universal formula to the correct exposure neither is there a general exposure for images. It all depends on how artistic a photographer wants to be and the scene or mood to be portrayed. If an image is underexposed, then there should be an increase in the opening of the aperture and length of time of the shutter speed and for the overexposed image, the reverse is the case.
A mastery of the ISO, aperture and shutter speed is the major key to understanding photography, it goes beyond the exposure of an image.