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Psychophysical Interface

Understand modulation contrast, transfer functions, and threshold calculations for visual air quality evaluation. Discover utility functions and judgment perceptions.

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Psychophysical Interface

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  1. Psychophysical Interface • Thresholds (plume and landscape) • Judgments of visual air quality • Value assessment

  2. Different Kinds of Threshold Calculations

  3. Modulation Contrast (mean square radiance is the relative psychophysical variable) The mean square radiance associated with the above equation can be shown to equal where m is the modulation contrast, m=(Nm-Nb)/(Nm+Nb), is the average image radiance, and (1/2) is the mean square radiance fluctuation.

  4. Human Visual System Sensitivity

  5. Wave Types

  6. Sine Wave Grating

  7. Superposition Principle More complicated one-dimensional images can be represented as weighted sums of light and dark bars of various frequencies and intensities. Mathematically, where Nr(x) is the one dimensional image radiance field at an observer image distance r, ao is the average image radiance, , and an are the weighting factors associated with various sinusoid frequencies n2πfo.The second term, , is the modulation of average image radiance ao.

  8. Equivalent Contrast The mean square radiance associated with the above equation yields Comparison of two mean square radiance equations suggests that the second term in each of these equations can be set equal to each other to yield and

  9. Modulation Transfer Function The effect of an increase in atmospheric aerosol concentration on a complex scene is The modulation contrast of any sinusoid is then

  10. The Equation ...and the transfer of modulation contrast is

  11. Transfer of Equivalent Contrast If the change in scene equivalent contrast is a result of addition or subtraction of atmospheric aerosol, initial and final contrast are related to each other by where Mtf is the atmospheric modulation transfer function given by

  12. Quadratic Detection Model The quadratic detection model stated mathematically: where

  13. Cross Section of Haze Layer

  14. Power Spectra Without Plume

  15. Power Spectra Without Plume

  16. Modulation Transfer and Equivalent Contrast Substituting and solving for Mtf yields

  17. Proportionality Constant

  18. Modulation Transfer Function Surface For a One JNC Change

  19. JNC Surface (80% reduction in extinction)

  20. Plume Geometry

  21. Plume Contrast Calculation

  22. Computer Generated Plumes

  23. Contrast Level at Threshold of Detection vs. Plume Length and Edge Type

  24. Probability of Detection of 0.36 Degree Circular Plume vs. Modulation Contrast

  25. Predicted Probability of Detection vs. Modulation Contrast and Plume Width

  26. Modulation Contrasts of 3 Plume Types at a 70% Detection Threshold

  27. Contrast Level at Threshold of Detection vs. Plume Width

  28. Contrast Level at Threshold of Detection of 3 Plume Types vs. Plume Width

  29. Sine Wave Grating

  30. Thresholds vs Judgments of Visual Air Quality • Perceived Visual Air Quality (PVAQ) • Visual Air Quality Index (VAQI) • Scenic Beauty Estimate (SBE)

  31. Perceived Visual Air Quality vs. Particulate Concentration

  32. Perceived Visual Air Quality vs. Sun Angle and Sky Conditions

  33. Perceived Visual Air Quality vs. Distance to Vista

  34. Perceived Visual Air Quality vs. Time of Day

  35. La Sals -- 30km

  36. Perceived Visual Air Quality vs. Height of Plume

  37. Value Assessment of Visual Air Quality • Willingness to pay • Utility function (time and dollars) • Importance value • Visual air quality and behavior • Etc.

  38. Utility Function for Visual Air Quality

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