An incident light meter measures the light reaching its receptor, usually from the subject’s position. Exposure meters convert the measurement into a camera-setting recommendation using the selected sensitivity and exposure time or cine settings.
What the reading represents
The meter reads illumination at its position, so a dark costume and a pale costume do not change the reading simply because they reflect different amounts of light. Moving or turning the receptor can change the result. A hemispherical dome and a flat receptor have different purposes and angular responses.
Practical example
Before an actor walks through a doorway, take readings at the start and end marks with consistent receptor orientation. A one-stop difference means a two-to-one difference in the compared light levels. Decide whether to adjust the lighting, accept the change or plan an exposure adjustment; the meter does not decide the intended look.
Exposure readings and source comparisons
For an overall exposure reading, follow the meter’s guidance for dome position and orientation, commonly toward the camera from the subject. To compare individual lights, use the appropriate receptor configuration and isolate each contribution. Record ISO, frame rate, shutter angle or exposure time, and any compensation. Check the camera image for highlights, practicals and spectral effects that a single incident reading cannot describe.
Related terms
Reflected Light Meter · Lux · Stop · Lighting Ratio
References
Sekonic: incident and reflected metering · Sekonic: L-858D metering functions