Effects of Illumination Level on Visual Performance and Fatigue*

Ernst Simonson; Josef Brozek

doi:10.1364/JOSA.38.000384

Journal of the Optical Society of America
Vol. 38,
Issue 4,
pp. 384-397
(1948)
•https://doi.org/10.1364/JOSA.38.000384

Effects of Illumination Level on Visual Performance and Fatigue

Ernst Simonson and Josef Brozek

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Ernst Simonson and Josef Brozek, "Effects of Illumination Level on Visual Performance and Fatigue*," J. Opt. Soc. Am. 38, 384-397 (1948)

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Abstract

The purpose of this study was to investigate the relation of the level of illumination intensity to performance and fatigue in visual work. The question of illumination requirements is of considerable importance from the point of view of physiological optics, industrial physiology, and public health. Yet a large part of the research done in the past leaves much to be desired in regard to general approach and specific testing techniques as well as experimental analysis and statistical evaluation. In the present series six illumination levels (2, 5, 15, 50, 100, and 300 footcandles) were studied in repeated experiments in six normal subjects. The work task involved recognition of fine details (letters) and reproduced the essential features of a conveyor inspection operation. In addition to the studying of various criteria of work performance and their change in the course of 2 hours of work, a large battery of visual tests was applied before and after the work so as to characterize the degree of fatigue. Varied illumination affected the performance more than the functional criteria of fatigue. Only one function, the recognition time for stimuli of threshold size, showed a decreasing degree of fatigue up to 300 ft.-c, all other variables, including performance, which changed with a changing level of illumination showed an optimum at 100 ft.-c. The demonstration of an optimum level of illumination makes highly questionable the current practice of recommending “minimum” levels of illumination for industrial jobs, since deterioration of performance and increase in fatigue may result when the optimal level is exceeded. The optimum of 100 ft.-c for the present strenuous visual task is at or below the minimum which should be recommended on the basis of the code of the Illuminating Engineering Society.

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Retinal functions	Units	“Desirable” values
Recognition time	Seconds	Lower
Flicker fusion frequency	Flashes per second	Higher
Brightness discrimination, green	Arbitrary units	Lower
Brightness discrimination, red	Arbitrary units	Lower
Ophthalmological Tests
Abduction	Diopters	Higher
Adduction	Diopters	Higher
Vertical divergence	Diopters	Higher
Accommodation near point	Centimeters	Lower
Convergence near point	Centimeters	Lower
Performance Criteria
Performance average	No. of correct letters	Higher
Performance drop	No. of correct letters	Lower
Performance range	No. of correct letters	Lower
Blinking Rate
Blinking rate average	Blinks per minute	Lower
Blinking rate difference start-finish	Blinks per minute	Lower
Questionnaire Score	Arbitrary units	Lower
Ophthalmographic Measurements
Movement phase	1/100 sec.	Lower
Angular velocity	Arbitrary units	Higher
No. of movement	Rate per second	Higher
Fixation phase	1/100 sec.	Lower
Extent of movement	Arbitrary units	Lower
Discrepancy	Arbitrary units	Lower

	Level of illumination
	5 ft.-c		100 ft.-c		300 ft.-c
Function	mean		mean		mean
Performance average	167.4		189.3		188.0
Performance range	22.6		9.2		12.9
Blinking rate average	9.77		5.80		8.32
	$\bar{d}$	F	$\bar{d}$	F	$\bar{d}$	F
Performance drop	−14.1	29.41**	−6.8	21.46**	−10.9	30.47**
Blinking rate difference	−0.83	1.01	−0.48	0.89	−0.72	0.90
Questionnaire score	−8.4	87.61**	−7.7	62.23**	−8.2	58.19**

	Compared levels of illumination
	5:100 ft.-c		5:300 ft.-c		100:300 ft.-c
Function	$\bar{Δ}$	F	$\bar{Δ}$	F	$\bar{Δ}$	F
Recognition time	−2.6	6.79*	−3.6	8.58**	−1.0	1.53
Performance average	−21.9	102.67**	−20.6	112.99**	1.3	1.57
Performance drop	−7.2	8.49**	−3.2	1.85	4.1	8.69**
Performance range	−13.4	40.72**	−9.6	17.38**	3.8	8.56**
Blinking rate average	−3.97	49.80**	−1.44	3.19	2.52	15.93**

	Level of illumination
	5 ft.-c		100 ft.-c		300 ft.-c
Function	$\bar{d}$	F	$\bar{d}$	F	$\bar{d}$	F
Recognition time	−3.69	16.55**	−1.10	3.69	−0.12	0.02
Flicker fusion frequency	−0.93	18.33**	−0.90	17.16**	−1.15	28.68**
Brightness discrimination, green	0.05	0.15	−0.12	1.31	−0.09	1.67
Brightness discrimination, red	−0.20	2.69	−0.03	0.08	0.04	0.25

	Level of illumination
	5 ft.-c		100 ft.-c		300 ft.-c
Function	$\bar{d}$	F	$\bar{d}$	F	$\bar{d}$	F
Abduction power	−0.11	0.34	−0.22	3.24	0.10	0.59
Adduction power	1.35	4.97*	0.88	1.90	0.82	3.10
Vertical divergence	0.01	0.006	−0.04	0.56	−0.01	0.05
Accommodation near point	−0.14	0.47	0.31	2.38	−0.01	0.005
Convergence near point	−0.08	0.27	−0.17	2.24	−0.15	1.11

		Illumination level ft.-c significance
Subjects	Lamp	5	15	50	100	300	50:100	100:300	50:300
6 trained	Frosted	5	3.7	2.2	1.7	2.5	**	**	no
14 untrained	Frosted	5	3.9	2.4	1.3	2.5	**	**	no
6 trained	Natural white	5	3.7	2.2	1.8	2.3	**	**	no
14 untrained	Natural white	5	3.7	2.5	1.3	2.5	**	**	no
6 trained	Verd-A-Ray	4.8	3.5	2.2	1.8	2.8	*	**	no
14 untrained	Verd-A-Ray	4.9	3.9	2.3	1.5	2.5	*	**	no

	Level of illumination
	5 ft.-c		100 ft.-c		300 ft.-c
Function	$\bar{d}$	F	$\bar{d}$	F	$\bar{d}$	F
Movement phase	−0.87	5.94*	−0.15	0.57	−0.18	0.42
Angular velocity	−0.53	2.42	−0.27	0.83	0.03	0.005
No. of movements	−0.18	7.87***	−0.26	30.00***	−0.25	10.71***
No. of movements	−0.19	4.46	−0.24	10.86**	−0.18	1.18
Fixation phase	−1.10	1.32	−1.48	5.48*	−1.36	2.64
Extent of movement during fixation phase	−0.5	2.65	−0.21	0.84	0.38	0.78
Discrepancy between fixation point and target	−0.15	0.18	−0.64	2.40	−0.45	0.93

	Level of illumination
	5 ft.-c		100 ft.-c		300 ft.-c
Function	$\bar{d}$	F	$\bar{d}$	F	$\bar{d}$	F
Movement phase	−0.87	5.94*	−0.15	0.57	−0.18	0.42
Angular velocity	−0.53	2.42	−0.27	0.83	0.03	0.005
No. of movements	−0.18	7.87***	−0.26	30.00***	−0.25	10.71***
No. of movements	−0.19	4.46	−0.24	10.86**	−0.18	1.18
Fixation phase	−1.10	1.32	−1.48	5.48*	−1.36	2.64
Extent of movement during fixation phase	−0.5	2.65	−0.21	0.84	0.38	0.78
Discrepancy between fixation point and target	−0.15	0.18	−0.64	2.40	−0.45	0.93

Abstract

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Figures (7)

Tables (7)

Equations (8)

Journal of the Optical Society of America