A camera is being used with a correct exposure at f / 4 and...

A camera is being used with a correct exposure at $f / 4$ and a shutter speed of $(1 / 16)$ s. In order to photograph a rapidly moving subject, the shutter speed is changed to $(1 / 128)$ s. Find the new $f$ -number setting needed to maintain satisfactory exposure.

Key Concepts

Exposure Triangle

This concept refers to the fundamental relationship among aperture, shutter speed, and sensor sensitivity (ISO) in photography. These three factors work together to control the exposure of an image, and adjusting any one of them requires compensatory changes in the others to maintain a balanced exposure.

Aperture (f-number) and Light Gathering

Aperture, indicated by the f-number, represents the size of the opening in a lens that lets light in. The amount of light that passes through is proportional to the area of the aperture, which is inversely proportional to the square of the f-number. Therefore, a lower f-number results in a larger aperture opening, allowing more light to hit the sensor.

Shutter Speed

Shutter speed determines the duration for which the camera’s sensor is exposed to light. Faster shutter speeds reduce the time available for light to enter the camera, resulting in less exposure, while slower speeds increase exposure by allowing more light in. This setting is crucial when photographing moving subjects to control motion blur.

Compensatory Adjustments in Exposure

When one exposure setting is altered, such as changing the shutter speed to better capture motion, compensatory adjustments must be made to other settings like the aperture to retain a similar exposure level. This involves understanding the mathematical relationships between these variables, such as the square law linking the f-number to the amount of light entering the camera.

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