Measurement of the Contrast Rendition Factor for Pencil Handwritten Tasks

This paper examines a procedure for assessment of the difficulty of pencil-handwritten visual tasks by physical measurement of the flux contrast of special pencil targets.

The author recently reported the conceptual framework of a new and more complete method to be used in specifying levels of interior illumination on the basis of visual performance criteria. The new method takes account of five factors which influence the difficulty of a visual task and hence the level of illumination to be specified, in addition to the intrinsic task variables such as size of detail, luminance and chromatic contrast and legibility. The new variables are: (a) the informational requirement of the task; (b) the angle at which the task is viewed; (c) the level of task object contrast in an actual environment, which depends upon the degree of veiling reflections present; (d) the level of task image contrast which depends upon the degree of disability glare in the environment; and (e) the level of visual performance capability in the presence of transitional adaptation, which depends upon the luminance non-uniformities in the actual environment.