Understanding Perspective with Grid Drawing

A perspective drawing goes wrong in one of two ways: the vanishing points move while you work, or the spacing between receding elements is guessed. Both are measurable errors, and both have a construction that fixes them. This page gives you those constructions, and it is careful about one thing most grid tutorials get wrong: a grid drawn on a photograph and a grid drawn in perspective space are different tools, and they cannot do each other's job.

Two Different Grids, and Why the Difference Matters

The word grid is doing two jobs on this page, and mixing them is the most common way a perspective study goes wrong.

A reference grid is the one you lay over a photograph. Its squares are equal on the paper, and that is its whole value: it lets you copy what the camera already worked out. It measures the picture, not the space. Squares two rows apart hold no information about how far apart the things inside them are.