Cornell University Ergonomics Web

Lighting Visibility Calculator

As the workforce ages there is a need for greater light levels on paper documents in offices, while at the same time for computer screen work there is a desire for lower light levels. This calculator estimates the illuminance required on a target to achieve the same visibility for people of different ages. You input the measured light level into the calculator, and if then estimates the required light level for equivalent visibility for people of different ages and tasks requiring different visual demands. The estimated equivalent light levels are based on data on the increase in the optical density of structures in the eye as a person ages. Use the visibility calculator to help you choose the an appropriate light level (illuminance) for a person and the work they are doing.

Cornell Visibility Calculator
This calculator estimates the light level needed for a level of visibility that is equivalent to what a 20 years old person sees at the light level that has been specified. It assumes that the target will be reflective (e.g. paper) and that it will have a good contrast level.
Input your Office Light Level (footcandles) here then click the "Update" button
    to execute the calculation
small target
IESNA Recommended Light Level (fc) 30 50 100
Employee Age (years) Required light level for equivalent visibility (fc) Required light level for equivalent visibility (fc) Required light level for equivalent visibility (fc)
Also remember that aging eyes:      
Need more light, especially for low contrast tasks.      
Are more sensitive to glare.      
Function better with high contrast.      
Need better lighting uniformity.      
Take longer to refocus, especially in dim light      
*NOTE: High contrast, small target is equivalent to Low contrast, large target  
CONVERSION: 1 footcandle =- 10.76 lux  
© Prof. Alan Hedge, Cornell University, Sep. 2008      

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