Understanding the basic functions of the camera requires an in depth understanding of the relationship between aperture, shutter and ISO. Mastering these makes camera operation second nature and allows you to concentrate on the image rather than the process of taking it. The camera records light and the amount of light that is captured is dependent on the amount that is presented to the sensor. This is a function of aperture and shutter where the aperture determines the amount of light that passes through the lens and the shutter the time the sensor is exposed to the available light. Aperture can be equated to the iris, in that a large f stop number of f/22 is a relatively small pupil that allows less light through, while an aperture number of f/2.8 is effectively a wide pupil or in other words allows the maximum amount of light to reach the retina or sensor. In order to achieve the correct exposure the amount of light passing through the lens, defined by the aperture setting and sensor sensitivity to the light is controlled by the shutter.
The relationship between these three elements are vital to capture the image correctly, i.e. exposure. The shutter is effectively a door that is opened for a predetermined time to allow for the correct exposure of the image given the amount of light passing through as defined by the light meter and the sensitivity of the sensor to that light. Sensitivity is defined by the ISO number, where the higher the number the greater the sensitivity and the less time is needed for the shutter to be open for the correct exposure. There is a trade off with high ISO and that is digital noise or grain. This can be a creative tool that can be used to add mood to an image. Similarly aperture can be used to control depth of field to enhance an element of an image, such as a nature shot with a bird taken at f/2.8 will make any distracting detail blurred in the background. Panning is another creative feature, where a slower shutter for correct exposure of a fast moving subject can bring it into sharp relief with a blurred background such as a motorbike.
The relationship between these three elements are vital to capture the image correctly, i.e. exposure. The shutter is effectively a door that is opened for a predetermined time to allow for the correct exposure of the image given the amount of light passing through as defined by the light meter and the sensitivity of the sensor to that light. Sensitivity is defined by the ISO number, where the higher the number the greater the sensitivity and the less time is needed for the shutter to be open for the correct exposure. There is a trade off with high ISO and that is digital noise or grain. This can be a creative tool that can be used to add mood to an image. Similarly aperture can be used to control depth of field to enhance an element of an image, such as a nature shot with a bird taken at f/2.8 will make any distracting detail blurred in the background. Panning is another creative feature, where a slower shutter for correct exposure of a fast moving subject can bring it into sharp relief with a blurred background such as a motorbike.
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