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Emergent Techniques for Assessment of Visual Performance (1985) / Chapter Skim
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CONTRAST SENSITIVITY FUNCTION
Pages 2-13

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From page 2...
... from audition, the range of spatial frequencies usually measured by the contrast sensitivity function is about 10 octaves. A low spatial frequency consists of broad black and white bands; a high spatial
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From page 3...
... and horizontal luminance profiles (right) of vertical sinusoidal grating patterns, electronically generated at three levels of contrast.
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From page 4...
... Relationship Between Acuity and Contrast Sensitivity Visual acuity, because it is measured in terms of the smallest identifiable, high-contrast target, and because small sizes correspond to high spatial frequencies, measures visual sensitivity largely in the higher frequency regions of the contrast sensitivity function. In brief, visual acuity is measured in terms of the size of the critical detail (stroke width of the Snellen letter, for example)
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From page 5...
... Extensive psychophysical data that deal with abnormal contrast sensitivity and individual differences in contrast sensitivity functions, independence of contrast thresholds at different spatial frequencies, and masking and adaptation experiments lead us to conclude that the answer is no. FIGURE 3 Photopic contrast sensitivity function showing the range of spatial frequencies necessary to achieve a visual acuity of 1.0 with Snellen letters.
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From page 6...
... . The contrast sensitivity function has the potential of adding more information about the functioning of the visual system than that given by visual acuity, because it assesses sensitivity over a wide range of spatial frequencies, while visual acuity measures primarily sensitivity at the high spatial frequencies.
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From page 7...
... This dissociation between visual acuity and contrast sensitivity has been found in patients; but what about people with "normal" vision? Figure 6 illustrates three different contrast sensitivity functions from three Air Force pilots having visual acuities of 1.33, 1.00, and 0.80.
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From page 8...
... . The upper plot shows two contrast sensitivity functions: the average contrast sensitivity functions of normal subjects with acuity of 1.0 (smooth curve)
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From page 9...
... Copyright 1981 by the Air Force Aerospace Medical Research Laboratory. Visual Acuity and Contrast Sensitivity Function in Normal Vision While visual acuity cannot predict the spatial contrast sensitivity function in people with abnormal vision, visual acuity also cannot predict contrast sensitivity in people with assumed normal vision.
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From page 10...
... Contrast Sensitivity Function and Visual Performance Because the image of any object can be described as a set of spatial frequencies at various orientations, amplitudes, and phases (see Appendix C) , there is the potential that an observers contrast sensitivity function can be used to predict visual performance with more complex visual material.
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From page 11...
... These observers had their contrast thresholds measured for the detection and identification of both letters of the alphabet and airplanes of different angular size. The individual differences seen in the detection and identification of letters and planes were predictable from the relevant spatial frequencies of those targets required for detection and identification and the individual contrast sensitivity functions.
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From page 12...
... Copyright 1981 by the Air Force Aerospace Medical Research Laboratory.
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From page 13...
... This complication does not deter the working group from looking at the empirical evidence relating to the usefulness of the contrast sensitivity function in predicting visual processing of complex targets. Sensitivity to Phase The spatial phases of the sinusoidal components of complex patterns are as important as their amplitudes.
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Key Terms

  • sensitivity function
  • spatial frequencies
  • visual acuity
  • sensitivity functions
  • individual differences

  • spatial frequency
  • visual performance
  • visual acuities
  • target detection
  • photopic contrast

  • human visual
  • frequency content
  • acuity measurements
  • predict contrast
  • human contrast

  • peak contrast
  • contrast thresholds
  • frequency sensitivity
  • predict visual
  • visual tasks

  • low spatial
  • low photopic
  • acuity measures
  • individual variation
  • sinusoidal grating

  • photopic levels
  • normal vision
  • predicting detection
  • abnormal vision
  • contour density


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