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.