FAQ: What are optimal values for the Pupil and Corneal Reflection thresholds?

[Sam]

When the Pupil is properly thresholded (i.e., fully filled in blue with no additional blue in the iris), its threshold value should be at least 75. If lower than 75, the eye needs more illumination. The level of illumination can be adjusted via the Illuminator Power setting on the Camera Setup screen, and / or by moving the illuminator closer to the participant.

• If using the Long Range mount, the illumation level can be increased by pulling the illuminator’s focusing lens out towards the participant and / or by checking the positioning of the illuminator to ensure it is properly directed towards the participant's eye. See How do I point / focus the illuminator on the Long Range mount? for more information.
  

Once the illumination is adjusted, make sure the Corneal Reflection is properly thresholded (fully filled in light-blue with no additional thresholding in the sclera) without worrying too much about its threshold value, as long as it is below 255.