Abstract

Three experiments were performed (a) to derive indices of spatial summation for flickering white and three part-spectrum targets, on the assumption, verified in a previous experiment, that the index was the ratio of the slopes of the functions for CFF/log area and CFF/log luminance and (b) to investigate the effect of target/surround contrast on these functions.

It was found that, for part-spectrum targets at least, spectral composition is not a determinant of CFF and luminance is the effective variable. Further, the slope of the CFF/log luminance function increases with target area, depending upon the contrast between target and surround. It is suggested that these effects can be accounted for by postulating a family of sigmoid curves, representing the slope of the CFF/log luminance function as a function of log target size, with contrast as the parameter. These curves would have common upper and lower asymptotes, the points of inflection depending on the contrast.

© 1964 Optical Society of America

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References

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  1. R. A. Weale, Natl. Phys. Lab. Grt. Brit. Proc. Symp. 8, 447–459 (1957).
  2. P. J. Foley, J. Opt. Soc. Am. 51, 737–740 (1961).
    [Crossref] [PubMed]
  3. S. Hecht and S. Shlaer, J. Gen. Physiol. 19, 965–979 (1936).
  4. C. Landis, Physiol. Rev. 34, 259–286 (1954).
    [PubMed]
  5. A. Giorgi, J. Opt. Soc. Am. 53, 480–486 (1963).
    [Crossref] [PubMed]
  6. P. J. Foley, J. Opt. Soc. Am. 53, 975–977 (1963).
    [Crossref] [PubMed]
  7. If N>Nc, the observer cannot detect that the real luminance L, is varying over time; the impression he receives is that of a perfectly constant luminance Lm, the value of which is given by Talbot’s law, i.e., Lm=1t∫0tLdt.
  8. The lowest data points have the same contrast as the points immediately above. It is assumed that the differences are due to noise, and therefore the best fit for the theoretical line would be between them.

1963 (2)

1961 (1)

1957 (1)

R. A. Weale, Natl. Phys. Lab. Grt. Brit. Proc. Symp. 8, 447–459 (1957).

1954 (1)

C. Landis, Physiol. Rev. 34, 259–286 (1954).
[PubMed]

1936 (1)

S. Hecht and S. Shlaer, J. Gen. Physiol. 19, 965–979 (1936).

Foley, P. J.

Giorgi, A.

Hecht, S.

S. Hecht and S. Shlaer, J. Gen. Physiol. 19, 965–979 (1936).

Landis, C.

C. Landis, Physiol. Rev. 34, 259–286 (1954).
[PubMed]

Shlaer, S.

S. Hecht and S. Shlaer, J. Gen. Physiol. 19, 965–979 (1936).

Weale, R. A.

R. A. Weale, Natl. Phys. Lab. Grt. Brit. Proc. Symp. 8, 447–459 (1957).

J. Gen. Physiol. (1)

S. Hecht and S. Shlaer, J. Gen. Physiol. 19, 965–979 (1936).

J. Opt. Soc. Am. (3)

Natl. Phys. Lab. Grt. Brit. Proc. Symp. (1)

R. A. Weale, Natl. Phys. Lab. Grt. Brit. Proc. Symp. 8, 447–459 (1957).

Physiol. Rev. (1)

C. Landis, Physiol. Rev. 34, 259–286 (1954).
[PubMed]

Other (2)

If N>Nc, the observer cannot detect that the real luminance L, is varying over time; the impression he receives is that of a perfectly constant luminance Lm, the value of which is given by Talbot’s law, i.e., Lm=1t∫0tLdt.

The lowest data points have the same contrast as the points immediately above. It is assumed that the differences are due to noise, and therefore the best fit for the theoretical line would be between them.

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Figures (6)

Fig. 1
Fig. 1

Diagram of the apparatus used in Experiment I—not to scale.

Fig. 2
Fig. 2

Critical flicker frequency as a function of log target luminance, for four target sizes and for white and three part-spectrum lights, for five color-normal subjects.

Fig. 3
Fig. 3

Critical flicker frequency as a function of log target luminance for four target sizes and for white and two part-spectrum lights, for two protan subjects.

Fig. 4
Fig. 4

Critical flicker frequency as a function of log target luminance for four target sizes and for two target/surround contrasts: (a) c=9 and (b) c=0.

Fig. 5
Fig. 5

Critical flicker frequency as a function of log target luminance, for four target sizes, with no surround.

Fig. 6
Fig. 6

Slope of the CFF/log luminance function, as a function of log target diameter, for three target-surround contrast levels. The dotted lines represent suggested possible limits and progression of a family of such curves, with contrast as the parameter.

Tables (2)

Tables Icon

Table I Mean CFF, cycles per second, based on five readings from each of five subjects for white light and three spectral bands, at three luminance levels and for four target sizes.

Tables Icon

Table II Mean CFF, cycles per second, based on five readings from each of two protans, for white light and three spectral bands, at three luminance levels and for four target sizes.

Equations (2)

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N c = k log Q + k ,
Lm=1t0tLdt.