Summary

The work reported here is an extension of earlier work on a statistical theory of visual thresholds. Experiments are reported in which the quantum noise limitation of visual thresholds is explored further by the deliberate addition of noise to the test patterns presented to the observers. A theoretical framework is developed to account for the influence of this noise and it is found that empirical observations show the principal characteristics predicted by this theoretical framework. This appears to confirm the validity of this approach to visual thresholds. It also provides a convenient means for predicting the response of the eye when used to observe the output of any imaging system in which noise is present