Practical implications of a new visual performance model

Recommendations of illuminance are imprecise for specifying visual perfomance in lighted environments. A more exact method of determining visual performance in alphanumeric reading tasks has now been proposed. Predictions of visual performance over the range of lighting levels and task contrasts commonly experienced in commercial environments are possible with the model. Predictions of age-related changes in visual performance are also possible. Examples are provided. The model is based on the philosophy of psychophysics of lighting first described and implemented experimentally by Weston fifty years ago, but it and the study on which it is based go further. It is important that practitioners understand this philosophy and that future studies also adhere to its principles.