Aperture Calibration

I emerged from the seed packet tent to test light penetration across the window frame. A fallen brass curtain hook lay curled on the painted sill beside a small strip of translucent parchment paper. Anchoring my stance against the wood grain, I sheathed my blade and slotted the parchment into the curved grip of the hook. With a calibrated tilt of my wrist, I set the entire assembly upright facing the morning beam. A sharp, rectangular sliver of amber light cast instantly across the sill, bisecting the shadows. Motion ceased. Alignment was exact.