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References

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  1. J. P. Guilford, Psychometric Methods (McGraw-Hill Book Company, Inc., New York, 1935), p. 170ff.
  2. Although only random differences are present in Fig. 5, the data of Fig. 6 exhibit a consistent trend of smaller h for larger stimuli. The differences in h between the largest stimulus and each of the other stimuli were tested for significance. Value of CRσ and of P(probability of a difference existing in the direction obtained) are presented:Stimulus size (ranked with respect to largest stimulus)CRσP21.830.96634.330.99999243.900.9999555.130.999997
  3. L. A. Jones, “Summary of American opinion, BS/ARP 18, British standard specification for fluorescent and phosphorescent paint,” Great Britain Ministry of Home Security. RC(C)85 (July, 1942).

Guilford, J. P.

J. P. Guilford, Psychometric Methods (McGraw-Hill Book Company, Inc., New York, 1935), p. 170ff.

Jones, L. A.

L. A. Jones, “Summary of American opinion, BS/ARP 18, British standard specification for fluorescent and phosphorescent paint,” Great Britain Ministry of Home Security. RC(C)85 (July, 1942).

Other (3)

J. P. Guilford, Psychometric Methods (McGraw-Hill Book Company, Inc., New York, 1935), p. 170ff.

Although only random differences are present in Fig. 5, the data of Fig. 6 exhibit a consistent trend of smaller h for larger stimuli. The differences in h between the largest stimulus and each of the other stimuli were tested for significance. Value of CRσ and of P(probability of a difference existing in the direction obtained) are presented:Stimulus size (ranked with respect to largest stimulus)CRσP21.830.96634.330.99999243.900.9999555.130.999997

L. A. Jones, “Summary of American opinion, BS/ARP 18, British standard specification for fluorescent and phosphorescent paint,” Great Britain Ministry of Home Security. RC(C)85 (July, 1942).

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Figures (18)

Fig. 1
Fig. 1

Sketch of laboratory. A plywood structure was installed within an existing framework. The large plywood room served as a field of standardized brightness (the observation room). To the right was located the main control room. To the left was a supplementary control room.

Fig. 2
Fig. 2

Floor plan of laboratory. Dimensions of the plywood room (observation room) were: length, 63 feet; height, 10 feet, and width at the narrowest points, 10 feet.

Fig. 3
Fig. 3

Observation room with standard illumination, viewed from observers’ stations.

Fig. 4
Fig. 4

View of observers’ stations.

Fig. 5
Fig. 5

The arithmetical mean of h values computed from individual probability curves, plotted against adaptation brightness.

Fig. 6
Fig. 6

The arithmetical mean of h values computed from individual probability curves, plotted against stimulus area.

Fig. 7
Fig. 7

Average probability curve.

Fig. 8
Fig. 8

Permanent recording of experimental data.

Fig. 9
Fig. 9

Apparatus for producing standard brightnesses of a test surface.

Fig. 10
Fig. 10

The arithmetical mean of threshold contrasts, computed from individual probability curves, plotted as a function of adaptation brightness for five stimulus areas.

Fig. 11
Fig. 11

Interpolations from Fig. 10. Each curve represents the relation between threshold contrast and stimulus area for a given adaptation brightness.

Fig. 12
Fig. 12

Interpolations from Fig. 10. The product of ΔB and stimulus area is plotted as a function of stimulus area for various adaptation brightnesses.

Fig. 13
Fig. 13

The arithmetical mean of threshold contrasts computed from individual probability curves, plotted as a function of adaptation brightness for five stimulus areas. The solid curves represent interpolations from Fig. 11.

Fig. 14
Fig. 14

Stimulus illuminating system.

Fig. 15
Fig. 15

The arithmetical mean of threshold contrasts computed from individual probability curves, plotted as a function of adaptation brightness for seven stimulus areas.

Fig. 16
Fig. 16

Interpolations from Fig. 15. Each curve represents the relation between threshold contrast and stimulus area for a given adaptation brightness.

Fig. 17
Fig. 17

“Critical visual angle” as a function of adaptation brightness. The area under the curve represents “point sources.”

Fig. 18
Fig. 18

Interpolations from Figs. 15 and 16. The relation between stimulus area and adaptation brightness for stimuli of various contrasts.

Tables (8)

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Table I Ophthalmological records.

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Table II Arithmetical mean threshold contrast. Stimuli brighter than surround (Part I). Angular subtense of stimulus (minutes of arc).

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Table III Interpolations from Fig. 10. Log (arithmetical mean threshold contrast).

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Table IV Arithmetical mean threshold ΔB (B0 = 0).

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Table V Arithmetical mean threshold contrast. Stimuli brighter than surround (Part II). Angular subtense of stimulus (minutes of arc).

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Table VI Arithmetical mean threshold contrast. Stimuli darker than surround (Part II). Angular subtense of stimulus (minutes of arc).

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Table VII Arithmetical mean threshold contrast. Stimuli brighter than surround (Part III). Angular subtense of stimuli (minutes of arc).

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Table VIII Log (arithmetical mean threshold contrast). Interpolations from Fig. 15.

Equations (1)

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C ( contrast ) = ( B s B 0 ) / B 0 for stmuli brighter than the observa - tion screen , = ( B 0 B s ) / B 0 for stmuli darker than the observa - tion screen .