Abstract

Contrast sensitivity and visual acuity data are used to derive a unified visual performance contour which describes the generalized improvement in visual performance resulting as task background luminance is increased. Factors which influence the difficulty of visual tasks are described, and examples are given of the degree of task background luminance, and hence illuminance, required to permit criterion levels of performance for sample tasks. Physical principles and devices are described which permit measurements of: (a) task object contrast, (b) the integral of ocular light scatter which reduces task image contrast, and (c) the joint effect of luminance differences in the environment which produce transitional adaptive effects on visual performance. These physical aspects of luminous environments are shown to influence visual performance in quantitative ways which may be assessed by reference to the standard performance contour. An over-all lighting performance index is derived which takes account of the task background luminance and these three other measures of the effects physical aspects of luminous environments have upon visual performance. Lighting performance indices are presented for five sample lighting installations, which reveal the overriding importance of other aspects of luminous environments than the level of illuminance they provide. The problem of predicting the over-all visual performance to be expected from specific luminous environments in advance of construction is discussed, and empirically derived calculational methods are described.

© 1967 Optical Society of America

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References

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  1. H. R. Blackwell, J. Opt. Soc. Am. 36, 624 (1946).
    [CrossRef] [PubMed]
  2. H. R. Blackwell, Illum. Engr. 47, 602 (1952).
  3. H. R. Blackwell, Illum. Engr. 50, 286 (1955).
  4. H. R. Blackwell, Illum. Engr. 54, 317 (1959).
  5. H. R. Blackwell, J. Opt. Soc. Am. 53, 129 (1963).
    [CrossRef]
  6. H. R. Blackwell, Illum. Engr. 59, 627 (1964).
  7. H. R. Blackwell, S. W. Smith, Compt. Rend., 15th Session, Commission Internationale de L’Éclairage, B, 249 (1964).
  8. H. R. Blackwell, J. Opt. Soc. Am. 42, 606 (1952).
    [CrossRef] [PubMed]
  9. H. R. Blackwell, B. S. Pritchard, J. G. Ohmart, J. Opt. Soc. Am. 54, 322 (1954).
    [CrossRef]
  10. H. R. Blackwell, J. Opt. Soc. Am. 53, 456 (1953).
    [CrossRef]
  11. L. M. Ginsburg, Am. J. Optom. 28, 605 (1951).
    [CrossRef]
  12. H. R. Blackwell, Psychophysical Thresholds: Experimental Studies of Methods of Measurement (University of MichiganEngr. Res. Bull. No. 36), p. 227, 1953.
  13. H. R. Blackwell, R. N. Schwab, B. S. Pritchard, Illum. Engr. 59, 277 (1964).
  14. D. M. Finch, Illum. Engr. 48, 517 (1953).
  15. S. Hecht, E. Mintz, J. Gen. Physiol. 22, 593 (1939).
    [CrossRef] [PubMed]
  16. P. Moon, D. E. Spencer, J. Opt. Soc. Am. 34, 605 (1944).
    [CrossRef]
  17. H. R. Blackwell, O. M. Blackwell, Illum. Engr. 62,September (1967).
  18. H. R. Blackwell, Lighting 79, No. 10, 40 (1963).
  19. J. M. Chorlton, H. F. Davidson, Illum. Engr. 54, 482 (1959).
  20. D. M. Finch, Illum. Engr. 54, 474 (1959).
  21. H. R. Blackwell, Illum. Engr. 58, 161 (1963).
  22. H. R. Blackwell, Illum. Engr. 58, 217 (1963).
  23. H. R. Blackwell, Illum. Engr. 60, 243 (1965).
  24. H. R. Blackwell, Lighting 80, No. 9, 44 (1964).
  25. H. R. Blackwell, Lighting 82, No. 11, 44 (1966).
  26. H. R. Blackwell, Illum. Engr. 58, 642 (1963).
  27. H. R. Blackwell, Am. Inst. Architects J. 40, 87 (1963).
  28. G. A. Fry, B. S. Pritchard, H. R. Blackwell, Illum. Engr. 58, 120 (1963).
  29. R. M. Boynton, Visibility Losses Caused by Sudden Luminance Changes (Preprint 67.07, Congress, International Commission on Illumination), p. 12, 1967.
  30. H. R. Blackwell, Lighting 83, No. 2, 44 (1967).
  31. H. R. Blackwell, Lighting 83, No. 3, 43 (1967).

1967

H. R. Blackwell, O. M. Blackwell, Illum. Engr. 62,September (1967).

H. R. Blackwell, Lighting 83, No. 2, 44 (1967).

H. R. Blackwell, Lighting 83, No. 3, 43 (1967).

1966

H. R. Blackwell, Lighting 82, No. 11, 44 (1966).

1965

H. R. Blackwell, Illum. Engr. 60, 243 (1965).

1964

H. R. Blackwell, Lighting 80, No. 9, 44 (1964).

H. R. Blackwell, Illum. Engr. 59, 627 (1964).

H. R. Blackwell, R. N. Schwab, B. S. Pritchard, Illum. Engr. 59, 277 (1964).

1963

H. R. Blackwell, Illum. Engr. 58, 161 (1963).

H. R. Blackwell, Illum. Engr. 58, 217 (1963).

H. R. Blackwell, Illum. Engr. 58, 642 (1963).

H. R. Blackwell, Am. Inst. Architects J. 40, 87 (1963).

G. A. Fry, B. S. Pritchard, H. R. Blackwell, Illum. Engr. 58, 120 (1963).

H. R. Blackwell, Lighting 79, No. 10, 40 (1963).

H. R. Blackwell, J. Opt. Soc. Am. 53, 129 (1963).
[CrossRef]

1959

J. M. Chorlton, H. F. Davidson, Illum. Engr. 54, 482 (1959).

D. M. Finch, Illum. Engr. 54, 474 (1959).

H. R. Blackwell, Illum. Engr. 54, 317 (1959).

1955

H. R. Blackwell, Illum. Engr. 50, 286 (1955).

1954

1953

H. R. Blackwell, J. Opt. Soc. Am. 53, 456 (1953).
[CrossRef]

D. M. Finch, Illum. Engr. 48, 517 (1953).

1952

H. R. Blackwell, Illum. Engr. 47, 602 (1952).

H. R. Blackwell, J. Opt. Soc. Am. 42, 606 (1952).
[CrossRef] [PubMed]

1951

L. M. Ginsburg, Am. J. Optom. 28, 605 (1951).
[CrossRef]

1946

1944

1939

S. Hecht, E. Mintz, J. Gen. Physiol. 22, 593 (1939).
[CrossRef] [PubMed]

Blackwell, H. R.

H. R. Blackwell, Lighting 83, No. 3, 43 (1967).

H. R. Blackwell, O. M. Blackwell, Illum. Engr. 62,September (1967).

H. R. Blackwell, Lighting 83, No. 2, 44 (1967).

H. R. Blackwell, Lighting 82, No. 11, 44 (1966).

H. R. Blackwell, Illum. Engr. 60, 243 (1965).

H. R. Blackwell, Lighting 80, No. 9, 44 (1964).

H. R. Blackwell, Illum. Engr. 59, 627 (1964).

H. R. Blackwell, R. N. Schwab, B. S. Pritchard, Illum. Engr. 59, 277 (1964).

H. R. Blackwell, Illum. Engr. 58, 642 (1963).

H. R. Blackwell, J. Opt. Soc. Am. 53, 129 (1963).
[CrossRef]

G. A. Fry, B. S. Pritchard, H. R. Blackwell, Illum. Engr. 58, 120 (1963).

H. R. Blackwell, Am. Inst. Architects J. 40, 87 (1963).

H. R. Blackwell, Illum. Engr. 58, 161 (1963).

H. R. Blackwell, Illum. Engr. 58, 217 (1963).

H. R. Blackwell, Lighting 79, No. 10, 40 (1963).

H. R. Blackwell, Illum. Engr. 54, 317 (1959).

H. R. Blackwell, Illum. Engr. 50, 286 (1955).

H. R. Blackwell, B. S. Pritchard, J. G. Ohmart, J. Opt. Soc. Am. 54, 322 (1954).
[CrossRef]

H. R. Blackwell, J. Opt. Soc. Am. 53, 456 (1953).
[CrossRef]

H. R. Blackwell, J. Opt. Soc. Am. 42, 606 (1952).
[CrossRef] [PubMed]

H. R. Blackwell, Illum. Engr. 47, 602 (1952).

H. R. Blackwell, J. Opt. Soc. Am. 36, 624 (1946).
[CrossRef] [PubMed]

H. R. Blackwell, Psychophysical Thresholds: Experimental Studies of Methods of Measurement (University of MichiganEngr. Res. Bull. No. 36), p. 227, 1953.

H. R. Blackwell, S. W. Smith, Compt. Rend., 15th Session, Commission Internationale de L’Éclairage, B, 249 (1964).

Blackwell, O. M.

H. R. Blackwell, O. M. Blackwell, Illum. Engr. 62,September (1967).

Boynton, R. M.

R. M. Boynton, Visibility Losses Caused by Sudden Luminance Changes (Preprint 67.07, Congress, International Commission on Illumination), p. 12, 1967.

Chorlton, J. M.

J. M. Chorlton, H. F. Davidson, Illum. Engr. 54, 482 (1959).

Davidson, H. F.

J. M. Chorlton, H. F. Davidson, Illum. Engr. 54, 482 (1959).

Finch, D. M.

D. M. Finch, Illum. Engr. 54, 474 (1959).

D. M. Finch, Illum. Engr. 48, 517 (1953).

Fry, G. A.

G. A. Fry, B. S. Pritchard, H. R. Blackwell, Illum. Engr. 58, 120 (1963).

Ginsburg, L. M.

L. M. Ginsburg, Am. J. Optom. 28, 605 (1951).
[CrossRef]

Hecht, S.

S. Hecht, E. Mintz, J. Gen. Physiol. 22, 593 (1939).
[CrossRef] [PubMed]

Mintz, E.

S. Hecht, E. Mintz, J. Gen. Physiol. 22, 593 (1939).
[CrossRef] [PubMed]

Moon, P.

Ohmart, J. G.

Pritchard, B. S.

H. R. Blackwell, R. N. Schwab, B. S. Pritchard, Illum. Engr. 59, 277 (1964).

G. A. Fry, B. S. Pritchard, H. R. Blackwell, Illum. Engr. 58, 120 (1963).

H. R. Blackwell, B. S. Pritchard, J. G. Ohmart, J. Opt. Soc. Am. 54, 322 (1954).
[CrossRef]

Schwab, R. N.

H. R. Blackwell, R. N. Schwab, B. S. Pritchard, Illum. Engr. 59, 277 (1964).

Smith, S. W.

H. R. Blackwell, S. W. Smith, Compt. Rend., 15th Session, Commission Internationale de L’Éclairage, B, 249 (1964).

Spencer, D. E.

Am. Inst. Architects J.

H. R. Blackwell, Am. Inst. Architects J. 40, 87 (1963).

Am. J. Optom.

L. M. Ginsburg, Am. J. Optom. 28, 605 (1951).
[CrossRef]

Illum. Engr.

H. R. Blackwell, R. N. Schwab, B. S. Pritchard, Illum. Engr. 59, 277 (1964).

D. M. Finch, Illum. Engr. 48, 517 (1953).

G. A. Fry, B. S. Pritchard, H. R. Blackwell, Illum. Engr. 58, 120 (1963).

H. R. Blackwell, O. M. Blackwell, Illum. Engr. 62,September (1967).

H. R. Blackwell, Illum. Engr. 58, 642 (1963).

H. R. Blackwell, Illum. Engr. 47, 602 (1952).

H. R. Blackwell, Illum. Engr. 50, 286 (1955).

H. R. Blackwell, Illum. Engr. 54, 317 (1959).

H. R. Blackwell, Illum. Engr. 59, 627 (1964).

J. M. Chorlton, H. F. Davidson, Illum. Engr. 54, 482 (1959).

D. M. Finch, Illum. Engr. 54, 474 (1959).

H. R. Blackwell, Illum. Engr. 58, 161 (1963).

H. R. Blackwell, Illum. Engr. 58, 217 (1963).

H. R. Blackwell, Illum. Engr. 60, 243 (1965).

J. Gen. Physiol.

S. Hecht, E. Mintz, J. Gen. Physiol. 22, 593 (1939).
[CrossRef] [PubMed]

J. Opt. Soc. Am.

Lighting

H. R. Blackwell, Lighting 83, No. 2, 44 (1967).

H. R. Blackwell, Lighting 83, No. 3, 43 (1967).

H. R. Blackwell, Lighting 79, No. 10, 40 (1963).

H. R. Blackwell, Lighting 80, No. 9, 44 (1964).

H. R. Blackwell, Lighting 82, No. 11, 44 (1966).

Other

H. R. Blackwell, S. W. Smith, Compt. Rend., 15th Session, Commission Internationale de L’Éclairage, B, 249 (1964).

R. M. Boynton, Visibility Losses Caused by Sudden Luminance Changes (Preprint 67.07, Congress, International Commission on Illumination), p. 12, 1967.

H. R. Blackwell, Psychophysical Thresholds: Experimental Studies of Methods of Measurement (University of MichiganEngr. Res. Bull. No. 36), p. 227, 1953.

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Figures (50)

Fig. 1
Fig. 1

Observers in light cube used for measuring contrast sensitivity as a function of luminance.

Fig. 2
Fig. 2

Equipment used to present luminance increments by transillumination of the screen in the light cube.

Fig. 3
Fig. 3

Percentage accuracy as a function of target contrast for typical detection experiment.

Fig. 4
Fig. 4

Threshold performance contours relating target contrast to background luminance for different target sizes at a fixed duration of 1 sec. The value xx in ft-L × 3.426 yields the value in cd/m2.

Fig. 5
Fig. 5

Threshold performance contours relating target contrast to background luminance for different target sizes at a fixed duration of 1/10 sec. The value xx in ft-L × 3.426 yields the value in cd/m2.

Fig. 6
Fig. 6

Threshold performance contour for a 4-min disk target presented for a ⅕-sec exposure. The value xx in ft-L × 3.426 yields the value in cd/m2.

Fig. 7
Fig. 7

The Field Task Simulator used to present a 4-min disk target under dynamic conditions involving ocular search and scanning.

Fig. 8
Fig. 8

Comparable data from the Field Task Simulator and light cube, showing the similarity of the shape of the performance contour, and the magnitude of the Field Factor needed to bring the two sets of data into agreement. The value xx in ft-L × 3.426 yields the value in cd/m2.

Fig. 9
Fig. 9

Standardized performance contour for detection of contrast ratio under conditions of ordinary seeing. The dashed line refers to the method of using the contour to prescribe illuminance for a task of interest. The value xx in ft-L × 3.426 yields the value in cd/m2.

Fig. 10
Fig. 10

Optical schematic of the simplified Visual Task Evaluator used to assess task difficulty by reducing contrast to the visibility threshold using a veil of unfocused light.

Fig. 11
Fig. 11

The simplified Visual Task Evaluator with a photometer controlled light veil.

Fig. 12
Fig. 12

The Visual Task Evaluator with the calibration unit providing a 4-min luminous disk target of variable physical contrast.

Fig. 13
Fig. 13

Optical elements of the equipment used to study visual acuity as a function of both physical contrast and background luminance.

Fig. 14
Fig. 14

Control console for the acuity measuring equipment.

Fig. 15
Fig. 15

Contrast sensitivity (solid line) and acuity data relating contrast to background luminance for a fixed performance criterion. The value xx in ft-L × 3.426 yields the value in cd/m2.

Fig. 16
Fig. 16

Sample of handwriting used in studies of informational factors and task difficulty.

Fig. 17
Fig. 17

Plan for a double hemisphere involving unusually good light diffusion.

Fig. 18
Fig. 18

Values of the Factor for Viewing Angle as a function of the Task Information Index for different viewing angles.

Fig. 19
Fig. 19

Values of the ratio FVA/TII as a function of Task Information Index, TII, for different viewing angles.

Fig. 20
Fig. 20

Components of the Visual Task Photometer (see text).

Fig. 21
Fig. 21

The portable sphere, a source of virtually perfectly diffuse illuminance for use as a standard in measurements of contrast rendition.

Fig. 22
Fig. 22

Production of a standardized multidot pencil target for physical study by the VTP.

Fig. 23
Fig. 23

Production of a standardized simulated pencil handwritten target for visual assessment by the VTE.

Fig. 24
Fig. 24

Test positions with the fixture layout. The room dimension is 8.5 m by 8.5 m.

Fig. 25
Fig. 25

Test positions with the ceiling layout. The room dimension is 8.5 m by 8.5 m.

Fig. 26
Fig. 26

The VTP mounted on a cart for convenient use in field testing in horizontal test positions.

Fig. 27
Fig. 27

The VTP mounted for field testing in vertical test positions.

Fig. 28
Fig. 28

Emittance characteristics of three lighting materials expressed in terms of relative luminance.

Fig. 29
Fig. 29

Construction for explanation of angular relations involved in describing measurements of plane-polarization test of radial symmetry of multilayer polarizer panels. L = luminaire plane, ψ = degree from normal, and Φ = degrees of rotation.

Fig. 30
Fig. 30

The polarization properties of a sample lighting material expressed in terms of a polargraph with different rotation angles represented by the shaded area. Multilayer polarizing panel.

Fig. 31
Fig. 31

Curvature of one-half the aspheric crater in a theoretical disability glare lens.

Fig. 32
Fig. 32

Results of calibration of the angular response of a sample disability glare lens in terms of the theoretical response curve.

Fig. 33
Fig. 33

Telephotometer set for measurement of luminance quantities for the horizontal test position. The special table was used.

Fig. 34
Fig. 34

Optical analog equipment including a disability glare lens (left), transitional adaptation lens with occluding mask (right), and special adaptor mount for the telephotometer (center).

Fig. 35
Fig. 35

Telephotometer with optical analog in place.

Fig. 36
Fig. 36

Data for the transitional adaptive effect of different luminance ratios with adaptation time as parameter (after Boynton).

Fig. 37
Fig. 37

Angular weighting coefficients based upon different assumptions concerning the probabilistic character of eye fixations around mean lines-of-sight.

Fig. 38
Fig. 38

Curvature of one-half the aspheric crater in a theoretical transitional adaptation lens.

Fig. 39
Fig. 39

Results of calibration of the angular response of a sample transitional adaptational lens in terms of the theoretical response curve.

Fig. 40
Fig. 40

The secondary photometric standard used to calibrate telephotometer readings for absolute luminance photometry.

Fig. 41
Fig. 41

Relation between the value of Equivalent Sphere Illumination (ft-c) and Task Visibility Index with a 70 ft-c (750 m-c) sphere reference illuminance. The value in ft-cd × 10.76 yields the value in meter-candles.

Fig. 42
Fig. 42

Telephotometer set for measurement of task contrast produced by a single ray of light of controlled plane-polarization.

Fig. 43
Fig. 43

Values of task reflectance for different single rays of horizontally plane-polarized light coming from the direction indicated on the axes. The task is a pencil dot viewed at 40° from vertical. Target 9.

Fig. 44
Fig. 44

Values of task reflectance for different single rays of vertically plane-polarized light coming from the direction indicated on the axes. The task is a pencil dot viewed at 40° from vertical. Target 9.

Fig. 45
Fig. 45

Values of task contrast for different single rays of horizontally plane-polarized light coming from the direction indicated on the axes. The task is a pencil dot viewed at 40° from vertical. Target 9.

Fig. 46
Fig. 46

Values of task contrast for different single rays of vertically plane-polarized light coming from the direction indicated on the axes. The task is a pencil dot viewed at 40° from vertical. Target 9.

Fig. 47
Fig. 47

The calculator used to predict visual performance for various installations of light fixtures.

Fig. 48
Fig. 48

The calculator used to predict visual performance for various installations of translucent ceilings.

Fig. 49
Fig. 49

The relative frequency with which different viewing angles are used, measured from the vertical.

Fig. 50
Fig. 50

The slotted ceiling mask for the portable sphere used to measure the Task Specularity Index.

Tables (22)

Tables Icon

Table I Values of the Required Luminance Br in ft-L,a as a Function of the Equivalent Contrast C

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Table II Experimental Values of CRF Target 30–4–2 Horizontal Task Location

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Table III Experimental Values of CRF Target 30–4–2 Vertical Task Location

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Table IV Experimental Values of DGF Horizontal Task Location

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Table V Experimental Values of DGF Vertical Task Location

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Table VI Values of the Variable k as a Function of θ

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Table VII Experimental Values of TAF Horizontal Task Location

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Table VIII Experimental Values of TAF Vertical Ceiling Location

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Table IX Individual Values of TAF Horizontal Task Location 40° Viewing Angle

Tables Icon

Table X Individual Values of TAF Vertical Task Location

Tables Icon

Table XI Values of Task Background Luminance Horizontal Task Location*

Tables Icon

Table XII Values of Task Background Luminance Vertical Task Location*

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Table XIII Task Background Reflectances Horizontal Task Location

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Table XIV Task Background Reflectances Vertical Task Location

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Table XV Values of CSF, 70 ft-c Sphere Reference Horizontal Task Location

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Table XVI Values of CSF, 70 ft-c Sphere Reference Vertical Task Location

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Table XVII Values of LPI and TVI Horizontal Task Location

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Table XVIII Values of LPI and TVI Vertical Task Location

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Table XIX Values of ESI (ft-c) Horizontal Task Location

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Table XX Values of ESI (ft-c) Vertical Task Location

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Table XXI Illuminance to Match 70 ft-c Sphere Reference Horizontal Task Location TVI = 1

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Table XXII Illuminance to Match 70 ft-c Sphere Reference Vertical Task Location TVI = 1

Equations (9)

Equations on this page are rendered with MathJax. Learn more.

C = Δ B / B ,
E r = B r / ρ ,
C f = ( B o - B ¯ ) / B o .
S ~ [ cos θ / θ ( θ + 1.5 ) ] ,
DGF = 1 / 1 + ( B v / B - 0.0526 ) ,
TAF = 1.015 - 0.0149 R .
P ~ exp ( - θ 2 / k ) ,
LPI = CSF × CRF × DGF × TAF .
C = | Σ E h R h C h + Σ E v R v C v Σ E h R h + Σ E v R v | ,

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