Find the eye inside your photograph

A photograph remembers where the camera stood

Every photograph was taken from one eye, at one height, pointing in one direction. That position is written into the picture: in the edges that lean towards each other, in the height of the horizon, in the way the upright lines of a building or a bottle tip inwards. Copy the photo blindly and you copy its accidents too. Read its geometry first, and you choose which ones to keep.

How to use it

• Find the edges. Look for things you know are parallel in the world: the two sides of a tablecloth stripe, the top and bottom of a book, tile joints, window frames. Drag each coloured pair onto two of them. The longer and further apart the edges, the truer the point.
• One point: for a view straight down a table, a road or a corridor. The blue pair finds the single point; the horizon runs level through it.
• Two points: for an object seen corner-on. Trace one family of edges in blue and the other in green; the line through the two points is the horizon, your eye level.
• Three points: trace two upright edges in pink. If they lean towards each other, the camera was tilted. Straighten the verticals removes that tilt, the way a camera on a level tripod would have seen the scene.
• Check a line: drag the orange line along any edge in your drawing or the photo, and it tells you which vanishing point it belongs to, or that it belongs to none.
• Proportional grid: choose your paper, and the grid shows a frame of the same shape over the photo, cut into squares, with the size of each square on your paper.

What a phone camera does to a still life

Phones use wide lenses and are usually held tilted down at a table. The result is a steep, looking-down view in which uprights lean towards a point far below the picture, and near objects look larger than they feel in the room. None of this is wrong, but it is rarely what the eye remembers. Decide your eye level, straighten what should stand upright, and paint what you saw rather than what the lens did.

Read the photograph before you copy it.