How the Eye Misjudges Neighbouring Lights
Simultaneous contrast: a less bright area beside dark looks brighter than a brighter area beside the sky
This red-chalk, text-only note warns the painter about simultaneous contrast when judging the strength of lights on a portrayed body. Leonardo observes that the eye is often deceived by comparison with the bordering areas: a less bright part set against dark looks brighter, while a brighter part set against a bright field such as the sky looks darker. The page is written in mirror script.
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The eye deceived by comparison of bordering brightnesses
When comparing the strength of lights on the lit parts of a portrayed body, the eye is often deceived, so that what is less bright seems brighter. If a less bright part borders dark areas and a brighter part borders bright areas such as the sky, the less bright appears more luminous and the brighter appears darker.