Step one

Measure the instrument before you measure yourself.

Three frames, a few seconds apart. Your skin cannot change in that time, so everything that differs between them is error, the camera, the angle, the light. That spread becomes the bar every future change has to clear.

Assay takes three frames a few seconds apart. Your skin cannot change in that time, so any difference between them is the instrument's error.

Use your own YouCam API key

The balance behind this deployment is finite and the four-day study spent most of it. Paste a YouCam API key here and every call runs on your units instead. It is held in this page only for as long as the tab is open: never saved to your browser, never written to disk on the server, never logged, and never used for anything but the requests you start. Reload the page and it is gone. Reading your balance costs nothing.

Upload 3 photographs

Uploading instead of using the camera needs 3 photographs of the same sitting, taken seconds apart without moving between them, face filling most of the frame. Not three different days, and not the same file three times: it is the small spread between near-identical photographs that measures the error, so three separate moments would measure your life instead of the instrument. Hold Ctrl, or Cmd on a Mac, to select them all at once.