Final answer:
Light meters are calibrated to 18% reflection to establish a standardized baseline for correct exposure, which is essential for photographers and videographers.
Therefore, the correct answer is: option a) 18
Step-by-step explanation:
A light meter (or illuminometer) is a device used to measure the amount of light.
In photography, an exposure meter is a light meter coupled to either a digital or analog calculator which displays the correct shutter speed and f-number for optimum exposure, given a certain lighting situation and film speed.
Most light meters are designed to average out a subject to match middle gray which reflects 18% of the light that falls on it. The correct option is (a) 18. This value is significant because it allows photographers and videographers to establish a standardized baseline for correct exposure in a scene.
To measure the light intensity, light meters use a sensor called a photodiode. A photodiode is a semiconductor that converts the incoming light to electrical current.
The sensor conducts electrical current directly proportional to the amount of light that it measures. Filters and built in lenses make up the photodiode.It is also a reference point for calibrating the brightness of monitors and printers in post-production workflows.