About the data set

Nachmias - psychometric function

This data set contains the measusrement of the psychometric function. The function describes how the probability of detection (y-axis) is related to the physical contrast of a stimulus (x-axis). The stimulus is a 9 cpd grating.

The blue crosses on the plot represent measurements, the red continous line is the fit of the psychometric function (Eq. 17 in the HDR-VDP-2 paper), and green circles are the prediction of the visual metric.

The data was reproduced from: Nachmias J, Sansbury RV. Letter: Grating contrast: discrimination may be better than detection. Vision research. 1974;14(10):1039-42.link; Figure 2, data 9 cpd grating, observer CS, open symbols curve (detection).

Stimuli list

All stimuli shown at the detection threshold magnified x10. The visible banding (quantization) is due to 8-bit image files and display panel and is not present in the actual data.

C=-0.000867

mean luminance = 30 cd/m²
surround_l = 30
viewing_distance = 0.9
rgb_display = crt
pixels_per_degree = 60
threshold_p = 2.76732e-05

C=0.00199014

mean luminance = 30 cd/m²
surround_l = 30
viewing_distance = 0.9
rgb_display = crt
pixels_per_degree = 60
threshold_p = 0.00307334

C=0.00484729

mean luminance = 30 cd/m²
surround_l = 30
viewing_distance = 0.9
rgb_display = crt
pixels_per_degree = 60
threshold_p = 0.0703099

C=0.00770443

mean luminance = 30 cd/m²
surround_l = 30
viewing_distance = 0.9
rgb_display = crt
pixels_per_degree = 60
threshold_p = 0.31519

C=0.0105616

mean luminance = 30 cd/m²
surround_l = 30
viewing_distance = 0.9
rgb_display = crt
pixels_per_degree = 60
threshold_p = 0.687143

C=0.0134187

mean luminance = 30 cd/m²
surround_l = 30
viewing_distance = 0.9
rgb_display = crt
pixels_per_degree = 60
threshold_p = 0.934254

C=0.0162759

mean luminance = 30 cd/m²
surround_l = 30
viewing_distance = 0.9
rgb_display = crt
pixels_per_degree = 60
threshold_p = 0.995513

C=0.019133

mean luminance = 30 cd/m²
surround_l = 30
viewing_distance = 0.9
rgb_display = crt
pixels_per_degree = 60
threshold_p = 0.999933