General office lighting visibility specifications were analyzed with respect to optimization of cost effectiveness. Cost effectiveness is a function of visual performance, not visibility per se. It was found that the present procedures which utilize ESI are not readily adaptable to cost optimization calculations. An alternative procedure using log VL is presented which appears suitable for this use. A sample calculation of net benefits versus light level is presented. For the same calculation the net benefits from visibility saturate at lower levels of visibility than are normally prescribed for office environments.