Illumination refers to the amount of light falling on a surface. Measuring illumination is key in cinematography to ensure adequate lighting conditions.

Here’s a converter that lets you easily convert foot-candles to lumens or lux and vice-versa:

## Key Terms and Units

**Lumens (lm)** quantify the total amount of visible light emitted by a source. Unlike Watts, which measures power, Lumens measure brightness.

**Lux (lx)** is the unit of measurement for illuminance, which describes how much luminous flux (light) is spread over a given area. One Lux equals one Lumen per square meter.

**Foot-candles (fc)** also measure illuminance in terms of Imperial units. One Foot-candle is equivalent to one Lumen per square foot.

**Exposure Value (EV)** is a measure of exposure for a given combination of aperture (f-number) and shutter speed. To convert EV to illuminance in lux, you need to consider the ISO sensitivity and use the following formula:

For example, for EV = 10 and ISO = 100:

Watts (W) measure the power consumption of a light source. It is not a direct measure of the amount of light produced but rather how much electrical energy the light uses.

The formula to calculate Lux is:

For example, if a light source emits 800 Lumens over an area of 10 square meters:

Similarly, the formula to calculate Foot-candles is:

For the same light source emitting 800 Lumens over an area of 100 square feet:

Since 1 square meter is approximately 10.764 square feet, the conversion between Lux and Foot-candles can be done using these formulas:

Illuminance decreases with the square of the distance from the light source. This is known as the inverse square law:

If you double the distance from the light source, the illuminance drops to one-quarter of its original value.