The method for establishing illumination requirements for various visual tasks developed by one of us and currently in use in the U.S.A. involves: A- the level of visual capacity to be provided by lighting B- the field factor to take account of condition of observation of a task; and C- methods of assessing the basic difficulty of a task. The present report contains further studies of B and C. Field factors were determined for luminous disc targets varying in size and informational content, using a field task simulator. Variations in these factors were found to be related primarily to the degree of off-axis viewing involved in performing the tasks. Task difficulty of both luminous disc and print sample tasks was studied both in the simulator and with a modified Visual Task Evaluator. Agreement between the results of the two methods of assessment was generally good, indicating the validity of the task evaluation method used.
Samenvatting