The speckled patch on the left looks paler and flatter than the one on the right. They are identical.
Try this
- Lower Contrast of the surround and the two patches start to match.
- Tick Hide the surround to compare them directly.
Why it happens
Your visual system judges contrast relative to the contrast nearby, the way it judges brightness relative to nearby brightness. Next to a high-contrast texture, a moderate one looks weaker. Charles Chubb, George Sperling and Joshua Solomon showed this in 1989 and found the effect is strongest when the surround and the center have similar textures, which points to the brain normalizing contrast across nearby areas.
Did you know?
It is also called contrast-contrast: not lightness, but the strength of the pattern itself is being compared.
References
- Chubb C., Sperling G., Solomon J. (1989). Texture interactions determine perceived contrast. Proceedings of the National Academy of Sciences, 86, 9631-9635. doi:10.1073/pnas.86.23.9631
- Background on Wikipedia
The illusion on this page is drawn by code written for this site. Last checked 1 November 2026.
Frequently asked questions
Are the two patches the same?
Yes, pixel for pixel. Hide the surround to check.
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