Adjust Sensitivity of all Optotypes (Letters, Numbers, Pictures, Rolling C's, and Tumbling E's). Adjust contrast, select single row, and adjust acuity level. Choose contrast range of rows. Hotkeys are available to choose rows and adjust sensitivity. Absolute measurement of contrast is dependant on your monitor. Percentage is relative to black (100%) and white (0%) as your monitor displays it. Note: 1% is barely visible on most screens and did not appear on the screen capture below.