NALMCO Certified Apprentice Lighting Technician (CALT) Practice Exam

Light level is measured in which unit?

1. Watts

2. Footcandles

3. Lumens

4. Electrons

The correct answer is: Footcandles

Light level, or illuminance, is commonly measured in footcandles. A footcandle is defined as the amount of light that falls on a surface one foot away from a uniform light source of one candlepower. This unit of measurement is crucial in lighting design and evaluation, as it quantifies how much light illuminates a given area, thus allowing professionals to determine if the lighting is adequate for a particular task. While lumens measure the total amount of light emitted by a source, footcandles specifically address how that light is distributed across a surface. Understanding the difference between these measures is essential for ensuring that lighting installations meet the necessary standards for visibility and comfort in various environments. Watts measure power consumption and do not directly correlate to light levels, while electrons refer to subatomic particles and are not applicable in this context. Therefore, footcandles is the correct unit for measuring light level in practical applications related to lighting.