Rather than researchers having to rely on manufacturers' specifications or an optical or engineering analysis, this paper provides a psychophysical method for determining the horizontal and vertical field of view of an HMD system. The technique employed makes use of a strobe light induced afterimage of two lights that subtend a predetermined size. This after image can then be used to set the width of two bars in the virtual environment and the number of pixels between the bars can be determined. Simple equations are provided to allow a determination of the basic dimensions of the display.