Speed, Accuracy, and VL
The contrast multiplier, or VL technique, was originally derived to describe the influence of contrast and illuminance upon the accuracy of detection or resolution. The CIE 19/2 model extended the technique to predict the performancekisibility relationship but it did not define performance beyond stating that it was some mix of speed and accuracy. The report was vigorously criticized for this, and other reasons, and the model has seen little acceptance. The reaction to the CIE model has been so adverse that Rea recently developed a performance/visibility model that avoids even introducing the VL concept. Rea actually fit only speed as a function of visibility, but he notes that the form of the accuracy data is not substantively different. The disadvantage of Reas approach is that it provides no explanation for why the VL technique provided good fits to simple accuracy data.