Illumination: Lux, Lumens & Foot-Candle Converter

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Published: May 29, 2024 | Last Updated: May 21, 2025

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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:

Conversion Type:
Value:

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Key Terms and Units

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

$\text{Illuminance (lux)} = \frac{125 \times 2^{\text{EV}}}{\text{ISO}}$

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

$\text{Illuminance (lux)} = \frac{125 \times 2^{10}}{100} = \frac{125 \times 1024}{100} = 1280 \text{ lux}$

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:

$\text{Lux} = \frac{\text{Lumens}}{\text{Area in square meters}}$

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

$\text{Lux} = \frac{800 \text{ lm}}{10 \text{ m}^2} = 80 \text{ lx}$

Similarly, the formula to calculate Foot-candles is:

$\text{Foot-candles} = \frac{\text{Lumens}}{\text{Area in square feet}}$

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

$\text{Foot-candles} = \frac{800 \text{ lm}}{100 \text{ ft}^2} = 8 \text{ fc}$

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

$1 \text{ fc} = 10.764 \text{ lx}$

$1 \text{ lx} = 0.0929 \text{ fc}$

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

$\text{Illuminance} \propto \frac{1}{\text{Distance}^2}$

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

Read Next: Want to explore how lighting transforms the mood of a scene?

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Or return to the Cinematography section for lenses, framing, and camera movement techniques.

By Jan Sørup

Jan Sørup is an indie filmmaker, videographer, and photographer from Denmark. He owns FilmDaft.com and the Danish company Apertura, which produces video content for big companies in Denmark and Scandinavia. Jan has a background in music, has drawn webcomics, and is a former lecturer at the University of Copenhagen.

View all of Jan Sørup's posts.