Matthew Luckiesh

Fatigue of Convergence Induced by Reading as a Function of Illumination Intensity

The decrement in the amplitude of convergence of the internal recti muscles due to reading for one hour under an intensity of illumination of one foot-candle was found to be three times as great as it was under 100 foot-candles. This symptom of ocular fatigue practically disappeared within a period of ten minutes after the cessation of the reading. The data were obtained by means of a recently designed convergence ergograph and possess a high degree of statistical reliability. These data provide additional evidence that at least 100 foot-candles are desirable for reading under usual conditions. From the Lighting Research Laboratory, General Electric Company.

The visibility of various type faces

Abstract In the absence of an adequate scale for evaluating any contributions to visual efficiency and human welfare, this phase of the present investigation may be presented in general terms.Perhaps the importance of type face, as a variable in seeing, is summarized by the viewpoint that modern visual tasks are so severe and exacting that any contribution towards ease in seeing is definitely worthwhile. Upon this basis, it would seem that the present method of appraising the visibility of type faces might well be applied generally, and in particular, to the type faces used in school text-books. Where the type faces are unchangeable it is seen that illumination (footcandles) can be used to obtain the desired degree of visibility or ease of reading.

The Perfect Reading Page

With the January 1937 issue, ELECTRICAL ENGINEERING presented to its readers the “easy reading” page. This article presents a discussion of the factors that would influence the production of a perfect reading page, and an opinion, founded upon scientific research, concerning this “easy reading” page as an approximation of the theoretical ideal.

Reflex Effects from Critical Seeing

Statistically reliable data are presented which indicate that the performance of critical visual tasks, such as reading, produces certain reflex effects which may be regarded as important criteria for revealing the expenditure of human energy in seeing. The experimental results indicate (1) that nervous muscular tension, developed as a result of reading for prolonged periods, decreases as the intensity of illumination under which the reading is done increases; and (2) that the heart rate progressively decreases as the duration of the visual task increases and that this decrement in the heart rate is much greater under one foot-candle than it is under 100 foot-candles. These reflex phenomena of an integrative character are correlated with experimental data pertaining to threshold visibility and used as criteria for determining desirable levels of illumination for close visual work.

Sampling devices for determining the bacterial content of air.

Appraisal of air contamination by micro‐organisms which are responsible for infectious diseases or result in spoilage of products requires devices for sampling the air to determine bacterial content. The simplest technique involves the use of open petri dishes containing culture media upon which colonies of the organisms can grow. However, quantitative data require the use of devices which will sample the bacterial content of definite volumes of air.Air samplers which yield quantitative data may be roughly divided into bubbler and impinger types. In the former type a definite quantity of air, with or without atomization, is bubbled through water, thus collecting a large part of the organisms. In the impinger types the organisms are deposited on the culture medium, either by use of high linear velocity of the air or by application of an electrostatic field.The authors have developed two types of impinger samplers. One of these, weighing approximately 12 pounds, employs an electrostatic field of about 7000 ...

Recommended footcandle levels for prolonged critical seeing.

Seeing is a complex human activity involving more than the visual sense and its ability to convert the stimulus, radiant energy, into sensations of brightness and color. Seeing is accomplished by the human being operating as a human seeing-machine. Therefore, efficient, certain, comfortable, and easy seeing involves psychophysiological factors and effects of seeing as well as the psychophysical characteristics of the visual task and its environment. There is some confusion and some difference of opinion in regard to levels of illumination that are now being recommended. This is not surprising inasmuch as recommended footcandle levels are very generally compromises involving many aspects of economics, practicability, and conservation. Adequate specifications of light, lighting, brightness, and color do not arise from a single study or even a limited group of studies. Pertinent data are yielded by researches along various major avenues involving achievement, conservation of human resources, subnormal as well as normal vision, supra-threshold as well as threshold visibility, and proper considerations of footcandle level as a means to the ends which are brightness level and visibility level. The author presents data and analyses which reply specifically to certain criticisms and which, he believes, support the conclusion that footcandle levels recommended by the Illuminating Engineering Society, as well as by himself and colleagues, are conservative in relation to the indicated ideal levels for various tasks of prolonged critical seeing.

Visibility and seeing

Abstract Visibility is defined as an attribute of the physical characteristics of the object of regard as determined introspectively by an observer possessing normal vision. Therefore seeing may be defined as a function of the visibility of the object and the visual efficiency of the observer. Techniques for the appraisal of visual efficiency have long been available to visual science; and techniques for the appraisal of visibility are needed in illuminating engineering and throughout all practices involving seeing.The significance of visibility, as a factor in seeing, is presented through the medium of correlations with certain psychophysiological effects resulting from seeing under conditions which afford various degrees of visibility. These analyses reveal that visibility and ease of seeing are closely related. The frequency of involuntary blinking has been developed as a criterion of ease of seeing and correlated with measurements of visibility. By these correlations, visibility measurements become of the utmost importance in the science of seeing whose most important objectives involve measurements and interpretations in the realm of supra-threshold seeing.

Visual Tasks in Sight-Saving Classes

The classification of low-vision subjects by the criterion of visual acuity may result in serious inconsistencies with respect to the actual visual efficiencies of the individuals. Visibility measurements are fundamentally sound and provide knowledge of broader significance and greater practical value. From the Lighting Research Laboratory, General Electric Company.

Researches in Seeing

Artificial illumination is usually inadequate and should be increased. Daylight should be approximated as nearly as possible. From the Lighting Research Laboratory of the General Electric Company, Nela Park, Cleveland. Read at the third annual meeting of the Association for Research in Ophthalmology, New Orleans, May 10, 1932.

A Correlation between Pupillary Area and Retinal Sensibility

An analysis of the experimental data from fifteen subjects indicates that the variation in retinal sensibility between the subjects is of the same order as the variation in the areas of the natural pupils. It is also evident that pupillary area and retinal sensibility are opposing factors with respect to their possible influence upon the level of illumination selected by an introspective appraisal of seeing. In general, the subjects with the larger pupils usually have the lower retinal sensibility, and vice versa. Differences in pupil size and in retinal sensibility account only in part for the wide differences in levels of illumination selected as desirable by various subjects for a given critical visual test, such as reading. Apparently these differences are not chiefly due to physiological factors associated with the visual sense. From the Lighting Research Laboratory of the General Electric Company.