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References

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  1. Work not yet published.
  2. H. Helson and J. P. Guilford, The Relation of Visual Sensitivity to the Amount of Retinal Pigmentation, J. Gen. Psych. 9, 58–76 (1933).
    [Crossref]
  3. P. W. Cobb, The Effect on Foveal Vision of Bright Surroundings—II, Psych. Rev. 21, 23–32 (1914).
    [Crossref]
  4. F. A. Geldard, Brightness Contrast and Heyman’s Law, J. Gen. Psych. 5, 191–206 (1931).
    [Crossref]
  5. We have used the unit, photon, as defined by Troland as the retinal illumination produced by a surface having a brightness of 1 c per sq. m when the pupillary aperture is 1 sq. mm (L. F. Troland, On the Measurement of Visual Stimulation Intensities, J. Exper. Psych. 2, 1–33 (1917)).
    [Crossref]

1933 (1)

H. Helson and J. P. Guilford, The Relation of Visual Sensitivity to the Amount of Retinal Pigmentation, J. Gen. Psych. 9, 58–76 (1933).
[Crossref]

1931 (1)

F. A. Geldard, Brightness Contrast and Heyman’s Law, J. Gen. Psych. 5, 191–206 (1931).
[Crossref]

1917 (1)

We have used the unit, photon, as defined by Troland as the retinal illumination produced by a surface having a brightness of 1 c per sq. m when the pupillary aperture is 1 sq. mm (L. F. Troland, On the Measurement of Visual Stimulation Intensities, J. Exper. Psych. 2, 1–33 (1917)).
[Crossref]

1914 (1)

P. W. Cobb, The Effect on Foveal Vision of Bright Surroundings—II, Psych. Rev. 21, 23–32 (1914).
[Crossref]

Cobb, P. W.

P. W. Cobb, The Effect on Foveal Vision of Bright Surroundings—II, Psych. Rev. 21, 23–32 (1914).
[Crossref]

Geldard, F. A.

F. A. Geldard, Brightness Contrast and Heyman’s Law, J. Gen. Psych. 5, 191–206 (1931).
[Crossref]

Guilford, J. P.

H. Helson and J. P. Guilford, The Relation of Visual Sensitivity to the Amount of Retinal Pigmentation, J. Gen. Psych. 9, 58–76 (1933).
[Crossref]

Helson, H.

H. Helson and J. P. Guilford, The Relation of Visual Sensitivity to the Amount of Retinal Pigmentation, J. Gen. Psych. 9, 58–76 (1933).
[Crossref]

Troland, L. F.

We have used the unit, photon, as defined by Troland as the retinal illumination produced by a surface having a brightness of 1 c per sq. m when the pupillary aperture is 1 sq. mm (L. F. Troland, On the Measurement of Visual Stimulation Intensities, J. Exper. Psych. 2, 1–33 (1917)).
[Crossref]

J. Exper. Psych. (1)

We have used the unit, photon, as defined by Troland as the retinal illumination produced by a surface having a brightness of 1 c per sq. m when the pupillary aperture is 1 sq. mm (L. F. Troland, On the Measurement of Visual Stimulation Intensities, J. Exper. Psych. 2, 1–33 (1917)).
[Crossref]

J. Gen. Psych. (2)

H. Helson and J. P. Guilford, The Relation of Visual Sensitivity to the Amount of Retinal Pigmentation, J. Gen. Psych. 9, 58–76 (1933).
[Crossref]

F. A. Geldard, Brightness Contrast and Heyman’s Law, J. Gen. Psych. 5, 191–206 (1931).
[Crossref]

Psych. Rev. (1)

P. W. Cobb, The Effect on Foveal Vision of Bright Surroundings—II, Psych. Rev. 21, 23–32 (1914).
[Crossref]

Other (1)

Work not yet published.

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Figures (10)

Fig. 1
Fig. 1

Diagram of the apparatus for measuring the stray light within the eye. A bright object in the periphery is provided by the illuminated aperture in front of lens I whose image is reflected by the right-angle prism to the eye. A disk-annulus test-object for measuring the effect of stray light upon the threshold at the fovea is provided by the differential threshold apparatus. The observer does not see the test-object directly but an inverted image on the face of lens IV. The light falling on the front end of the differential threshold apparatus from source V serves as a substitute for stray light, and provides a standard with which the effects of stray light can be compared.

Fig. 2
Fig. 2

The effect of increasing the stray light at the fovea upon the differential threshold.

Fig. 3
Fig. 3

The effect of increasing the “substitute stray light” upon the differential threshold.

Fig. 4
Fig. 4

The effect of displacing a bright object further and further toward the periphery upon the amount of stray light falling at the fovea, as measured by the change in the differential threshold. The amount of displacement is expressed in terms of the size of the visual angle subtended by the center of the test-object and the center of the peripheral object.

Fig. 5
Fig. 5

Diagram of the apparatus for demonstrating nervous interaction of the periphery with the fovea as manifested by the effect of a bright peripheral object upon the differential threshold at the fovea when a bipartite test-object is used. The illuminated aperture, C, serves as the bright peripheral object. The test-object consists of a bright disk one-half of which is covered by rice paper. Light from source W serves as a substitute for stray light and makes it possible to determine the role played by stray light.

Fig. 6
Fig. 6

A comparison between the conditions used by Geldard and the similar experiment by Bartley and Fry. In both cases the dimmer half of the test object was 0.59 as bright as the other.

Fig. 7
Fig. 7

A comparison of the results obtained by the present investigators with those obtained by Geldard in testing the effect of varying the brightness of a peripheral object upon the differential threshold at the fovea as measured with a bipartite test-object. The effect upon the differential threshold is expressed in terms of the brightness of the brighter half of the test object at which the two halves become just distinguishable, when the brightness ratio of the two halves is kept constant at 0.59.

Fig. 8
Fig. 8

The effect of varying the brightness of a peripheral object upon the differential threshold at the fovea, as measured with a bipartite test-object.

Fig. 9
Fig. 9

The effect of varying the brightness of the “substitute stray light” upon the differential threshold at the fovea as measured with a bipartite test-object.

Fig. 10
Fig. 10

An analysis of the curve in Fig. 7 showing the relative rôles played by stray light and nervous interaction.