Glare Ratings

Up to the present time, most discussions of glare have, of necessity, taken the form of general statements. It has often been emphasized by the writer that what we need in illuminating engineering is something much more specific, in fact, some simple way of arriving at a discomfort glare evaluation or "glare factor", for any lighting installation; preferable a method as simple as our ordinary methods of lighting calculation. You can visualize how fortunate we would be if, in submitting a design for office lighting, we could state that the installation would be "capable of supplying a maintained illumination of 40 footcandles and that its glare factor would not exceed 10, a figure safely below the accepted limit for office areas." Such a method of rating the discomfort factor in direct glare is about to be proposed to you; whether this proposal, or some modification of it, will stand all the tests to which it may be properly subjected, time alone will tell. Should such a method prove reliable, it does have the advantage of making it simple to compute and to compare on a common rating basis two or more dissimilar system of lighting.