Abstract

A résumé is presented of the results obtained in an extensive research into the many ways in which glare affects visibility.

Visibility was studied chiefly by the method of least perceptible contrasts of brightnesses. Results are presented showing the influence of adaptation and of form and size of test-object upon contrast sensitivity.

The results of the investigation show that the least perceptible brightness-difference between an object and its background increases directly with the illumination at the eye from the dazzle-source; varies approximately inversely with the square of the angle which the glare-source makes with the line of vision; and is practically independent of the brightness, size, type, distance, etc. of the dazzle-source.

Considerable study has been given to the variations of the pupil under steady, fluctuating, and glaring lights and of their influence upon vision. Results of the investigations upon irradiation, after-images, blinding-glare and light-shocks are also presented.

© 1926 Optical Society of America

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References

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  1. Luckiesh and Holladay, Tr. I. E. S.,  20, p. 221; 1925.
  2. Luckiesh, Taylor, and Holladay, J.O.S.A. & R.S.I.,  11, p. 311, Oct., 1925.
    [Crossref]
  3. J. P. C. Southall, Mirrors, Prisms, and Lenses, p. 448.
  4. Frank Allen, J.O.S.A. & R.S.I., p. 583; 1923.
    [Crossref]
  5. P. W. Cobb, Lectures on Ill. Eng.,  2, p. 525.
  6. C. V. Raman, Phil. Mag.,  38, p. 568; Nov., 1919.
    [Crossref]
  7. Rayleigh, Phil. Mag.,  41, pp. 107, 274, 447; 1917.

1925 (2)

Luckiesh and Holladay, Tr. I. E. S.,  20, p. 221; 1925.

Luckiesh, Taylor, and Holladay, J.O.S.A. & R.S.I.,  11, p. 311, Oct., 1925.
[Crossref]

1923 (1)

Frank Allen, J.O.S.A. & R.S.I., p. 583; 1923.
[Crossref]

1919 (1)

C. V. Raman, Phil. Mag.,  38, p. 568; Nov., 1919.
[Crossref]

1917 (1)

Rayleigh, Phil. Mag.,  41, pp. 107, 274, 447; 1917.

Allen, Frank

Frank Allen, J.O.S.A. & R.S.I., p. 583; 1923.
[Crossref]

Cobb, P. W.

P. W. Cobb, Lectures on Ill. Eng.,  2, p. 525.

Holladay,

Luckiesh and Holladay, Tr. I. E. S.,  20, p. 221; 1925.

Luckiesh, Taylor, and Holladay, J.O.S.A. & R.S.I.,  11, p. 311, Oct., 1925.
[Crossref]

Luckiesh,

Luckiesh, Taylor, and Holladay, J.O.S.A. & R.S.I.,  11, p. 311, Oct., 1925.
[Crossref]

Luckiesh and Holladay, Tr. I. E. S.,  20, p. 221; 1925.

Raman, C. V.

C. V. Raman, Phil. Mag.,  38, p. 568; Nov., 1919.
[Crossref]

Rayleigh,

Rayleigh, Phil. Mag.,  41, pp. 107, 274, 447; 1917.

Southall, J. P. C.

J. P. C. Southall, Mirrors, Prisms, and Lenses, p. 448.

Taylor,

Luckiesh, Taylor, and Holladay, J.O.S.A. & R.S.I.,  11, p. 311, Oct., 1925.
[Crossref]

J.O.S.A. & R.S.I. (2)

Frank Allen, J.O.S.A. & R.S.I., p. 583; 1923.
[Crossref]

Luckiesh, Taylor, and Holladay, J.O.S.A. & R.S.I.,  11, p. 311, Oct., 1925.
[Crossref]

Lectures on Ill. Eng. (1)

P. W. Cobb, Lectures on Ill. Eng.,  2, p. 525.

Phil. Mag. (2)

C. V. Raman, Phil. Mag.,  38, p. 568; Nov., 1919.
[Crossref]

Rayleigh, Phil. Mag.,  41, pp. 107, 274, 447; 1917.

Tr. I. E. S. (1)

Luckiesh and Holladay, Tr. I. E. S.,  20, p. 221; 1925.

Other (1)

J. P. C. Southall, Mirrors, Prisms, and Lenses, p. 448.

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Figures (40)

F. 1
F. 1

a, by reflection; b, by transmission; c, by scattering or diffusion.

F. 2
F. 2

Arrangement of apparatus used in investigating veiling-brightness.

F. 3
F. 3

Forms of test-objects employed in investigating glare and visibility.

F. 4
F. 4

a, with test-object shown at A in Fig. 3 when visual angle d = 1.1 min.; b, with test-object A when d = 4.1 min.; c, with test-object B when d = 5 min., and d, with test-object C when d = 4.25 min.

F. 5
F. 5

a, with photographic blue light; b, with Mazda C1 light; and C, with red light.

F. 6
F. 6

a, with test-object A; b, with test-object D.

F. 7
F. 7

a, with test-object A; b, with test-object D.

F. 8
F. 8

Diagram illustrating ease of seeing with various contrasts of brightness between test-object and background.

F. 9
F. 9

Arrangement of apparatus used in investigating dazzle-glare.

F. 10
F. 10

a and b, with test-object E when dazzle-source made angles D of 5 and 10 degrees respectively with the line of vision; c, with test-object C when D = 10.6 degrees.

F. 11
F. 11

Arrangement of apparatus used in the study of dazzle-glare.

F. 12
F. 12

Curve showing a straight line relationship between log EF and log D.

F. 13
F. 13

Showing that the least perceptible difference in brightness ΔF between a test-object and, Us background varies directly with the illumination E at the eye from the dazzle-source; and varies approximately inversely as the square of the angle D that it is elevated above the line of vision.

F. 14
F. 14

Arrangement of apparatus used in the comparative study of veiling-brightness and dazzle-glare.

F. 15
F. 15

Curve a shows the variation with angle D of the ratio of illumination E from the dazzle-source to the veiling-brightness B1 having an equal obscuring effect; curve b shows relation of EF to D.

F. 16
F. 16

Arrangement of apparatus used in studying the effect of relative positions of test-object and dazzle-source.

F. 17
F. 17

Arrangement of apparatus used in studying the effect of viewing a test-object through the center of the equivalent of an annular shaped dazzle-source.

F. 18
F. 18

Showing a straight line relationship between log EF and log (d − 0.5) for test-objects, D, when the dazzle-source is elevated 10 degrees above the line of vision.

F. 19
F. 19

Showing the average increase of the least perceptible difference in brightness with various strengths of positive or negative spherical lenses interposed in the line of vision of an emmetropic eye.

F. 20
F. 20

Showing a beam of light through the media of an eye where there is scattering of light from the media upon the fovea.

F. 21
F. 21

Curve a shows period of lime T1 in seconds for an after-image to decay to the apparent brightness F of the adapting field after the eyes had been preadapted to the brightness of F ml and then exposed for four seconds to a light-source of brightness B ml. Curve b shows the period of time T2 for the after-image, similarly formed, to decay so as to be unobservable when viewing any portion of the adapting field.

F. 22
F. 22

Showing the number of seconds T which must elapse after an exposure of the eyes for T0 seconds to a light source of brightness B ml before a test-object upon the screen can be seen, the eyes having been previously adapted to the brightness of F ml. The test-object is of form shown at D in Fig. 3 and visual angle d = 5 min.

F. 23
F. 23

Curves showing the visual angle A in min. of an opaque test-object rendered just invisible by irradiation due to viewing it against a background of brightness B2 ml, at five different adaptation brightnesses F of the surrounding field.

F. 24
F. 24

Curve a is plotted to logarithmic scales and curve b to arithmetic scales (upper and right-hand scales).

F. 25
F. 25

Showing the elation of brightness B in ml of light-source to the solid angle Q in steradians subtended by the projected area for “perceptibly uncomfortable” shocks of equal sensation when momentarily exposed, and when the background brightness F was 10 ml.

F. 26
F. 26

Showing relation of brightness B of light-source to its background brightness F for equal psycho-physiological sensations deemed “just not unpleasant.”

F. 27
F. 27

Sketch of double-pin-hole pupillometer.

F. 28
F. 28

Arrangement of apparatus used in the study of variations of diameter of the pupil.

F. 29
F. 29

Curves showing the variation of the pupil diameter P with brightness F of the adapting field for three observers. (Note different scales for ordinates.)

F. 30
F. 30

Curves showing relation of pupil diameter P to brightness F of adapting field for average eye. Equation, P = 7−.16F0.4 mm

F. 31
F. 31

Arrangement of apparatus used in investigating the effect upon the diameter of the pupil of flashes of unidirectional illumination.

F. 32
F. 32

Showing the number of milliamberts of uniform illumination having an equal effec upon the diameter of the pupil as one meter-candle at the eye from a dazzle-source located D degrees above the line of vision.

F. 33
F. 33

a is for F = 1/10 ml; b, for F = 1 ml; and c, for F = 10 ml.

F. 34
F. 34

Showing the relationship between relative contractions of pupil diameter and momentary increases of the general field brightness from F0 to F′ ml.

F. 35
F. 35

Curves showing the ratio of change of pupil diameter due to an increase of brightness of the general field from F0 to F′ ml when the adapting brightness F0 is 1/100, 1/10, 1, 10, and 100 ml respectively.

F. 36
F. 36

Curves showing the relation of contracted diameter P′ to initial diameter P0 of pupil of three observers for momentary flashes of unidirectional illumination E from a dazzle-source elevated 5, 10, and 15 degrees above the line of vision, when the eyes were pre-adapted to uniform brightness of F0 ml. (Note the different scales of ordinales.)

F. 37
F. 37

Showing the number of millilamberts momentary increase of uniform brightness of field having an equal effect in contracting the pupil as one meter-candle of unidirectional illumination at the eye from a dazzle-source located D degrees above the line of vision.

F. 38
F. 38

Showing the variation of the pupil diameter with distance R of the eye from the fixation point.

F. 39
F. 39

a, without change of the lens adjustment; b, with normal change of lens adjustment.

F. 40
F. 40

Showing the variation of pupil diameter with the illumination E at the eye from a light-source of uniform brightness B when viewed direct and whose projected area subtended a solid angle of Q steradians.

Tables (2)

Tables Icon

Table 1 Table showing the minimum difference in brightness, ΔF, between a test-object and its background at which the test-object was seen by each observer, for various positions of the test-object, when the angle D of the dazzle-source was 7.5 degrees and its illumination E, 31.5 mc.

Tables Icon

Table 2 Showing the results obtained by viewing a test-object through the center of an annular shaped dazzle-source.

Equations (39)

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total brightness = F 1 + B 1
Δ F 1 = 0.9 f 1 f f 1 F .
contrast sensitivity , S = F 1 + B 1 Δ F 1
Contrast sensitivity , S m ( d 0.5 ) 0.4
ease of seeing log ( Δ F / Δ F T )
Δ F = f 1 f f 1 F
E / Δ F is practically constant for a given angle D .
E / Δ F D 2.4
E / Δ F = 22.5 D 2
contrast sensitivity , S = ( F 1 + B 1 ) / Δ F 1
contrast sensitivity , S = F + K 1 ( E / D 2 ) Δ F
Δ F = F / S + ( K 1 / S ) ( E / D 2 )
B 1 = 4.3 E 1 D 1 2 + 4.3 E 2 D 2 2 · · = 4.3 E D 2 = 4.3 10 π B Q D 2
E = 10 B Q / π
B 1 = 4.3 10 π B d Q D 2
contrast sensitivity S = 43 ( d .5 ) .44
E / Δ F = 21 D 2 .
E P 2 cos D n Δ F = 370 D 1 . 8
I s I ( M M M ) 2 m T 2 λ 4 ( 1 + cos 2 q ) 1 r 2
d ϕ I s P 2 cos D n cos υ d l
d ϕ = ϕ = K 2 ( M M M ) 2 m T 2 λ 4 E P 2 j cot D n { cos D n + 4 3 cos 3 D n 2 3 cos 5 D n sin 2 D n 3 ( 1 sin 3 D n ) }
log T 1 = 1.26 log B 0.31 log F 4.49
F = ( B 1480 ) 4
log T 2 = 1.1 log B 0.31 log F 3.14
log T = 1.16 log B 0.32 log F + 0.9 log T 0 0.4 log f 1 f f 1 4.84
B 1 = ( B T 0 y T ) x
S = F + ( B T 0 5000 T ) 4 f 1 f f 1 F = 45 ( d 0.5 ) 0.4
A = 10.7 log B 2 2.07 log F 37.4 minutes
log B = 3.3 + 0.3 log F
K = log B + 0.25 log Q 0.3 log F
P = K 3 .16 ( F + C ) 0.4
P = 7 .16 F 0.4
equivalent millilamberts increase per meter‐candle = 1.85 ( 1.122 ) D
P = 7 .16 ( F + 1.85 ( 1.122 ) D E ) 0.4
P 0 P P 0 = 0.21 + 0.025 log F 0 + 0.205 log ( F F 0 F 0 )
F F 0 F 0 < 0.095 F 0 .122
P P 0 = 0.79 0.025 log F 0 0.205 log ( 1.4 E F 0 D 0.72 )
P 0 P P 0 = 0.21 + 0.025 log F 0 + 0.205 log ( 1.4 E F 0 D 0.72 ) = 0.21 0.18 log F 0 + 0.205 log ( 1.4 E D 0.72 )
P = 6.1 + 0.5 log Q log E or = 5.6 0.5 log Q log B