How does the Mars Letter Contrast Sensitivity Test differ from the Pelli-Robson Contrast Sensitivity Chart?
The Pelli-Robson uses triplets of letters at each contrast, and these decline in 0.15 log unit steps. The Mars test declines 0.04 log units in contrast from letter to letter. The scoring of the tests is different, as well. These differences result in the Mars test’s increase in accuracy of 28%. There are major physical differences as well. The Pelli-Robson is a large wall chart intended for viewing at 100 cm. The Mars test is handheld, and intended for 50 cm viewing distance. You can read more about technical differences between the tests here.
