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Footcandle Recommendations

IES specifies the recommended footcandle levels for different tasks for indoor and outdoor lighting. Let's look at these recommendations and how to calculate the appropriate light level for an application. Keep in mind that certain situations may call for higher levels than IES recommends. A work area for visually impaired workers, as an example.

Indoor IES light levels require a four-step process.

  1. The first step is to define the visual task. The important thing is the task contrast and size. This should be the most important task performed in a given area.
  2. The second step is to define the illuminance category, based on the visual task.
  3. The third step is to decide the illuminance range based on the previous category.
  4. And finally, the fourth step is to establish the illuminance target value based on age, accuracy and room or task surface reflectances. The fourth step uses weighting factors to decide the target value. Check the IES handbook to figure in these weighting factors.

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