Optical Correction

Numbers, letters, and shapes rarely appear "true" at size. Optical correction is the quiet craft of making things feel balanced even when they technically aren't.

A circle and a square with identical bounding boxes don't read as the same size. The circle appears smaller. To correct this, you make the circle slightly larger. Now it's the same size — not by measurement, but by perception. The math is wrong; the result is right.

Where optical correction appears

In type, the crossbar of an "H" is often drawn slightly thinner than the vertical strokes. If it were the same weight, it would read as heavier. Rounded letters like "O" and "C" extend beyond the baseline and cap height — otherwise they look too short. These adjustments are baked into every professional typeface, invisible until you look for them.

Icons follow the same rules. A diamond icon at the same pixel dimensions as a square appears smaller. Equilateral triangles look smaller than their siblings. Any icon with high verticality appears taller; any icon with high horizontality appears wider. Optical sizing requires breaking the grid to honor perception.

The deeper principle

Optical correction teaches a foundational lesson: design is communication between the object and the eye, not between the object and a ruler. The ruler is a starting point. The eye is the final judge. When the two disagree, the eye wins.