Actinic: Exposure Calculator

Actinic is a fast, fully offline exposure calculator built for film photographers — a film exposure calculator that also solves the one thing most light-meter apps skip: reciprocity failure on long exposures.

Dial in a Sunny 16 reading or your own aperture, shutter, and ISO, then read the full wheel of equivalent exposures instantly — no camera permissions, no accounts, no network calls, ever.

Shooting past a second? Pick your film stock — Tri-X, HP5 Plus, T-Max, Portra, Acros, and more — and Actinic corrects your exposure time for reciprocity failure using published manufacturer data, so your night shots and long exposures come out right the first time.

Included: • Full-stop exposure wheel with Sunny 16 quick-set • Reciprocity calculator with 3 built-in film stocks • Save up to 3 camera + film presets

Actinic Pro unlocks the full 12-stock reciprocity library, unlimited saved presets, and third-stop precision to match modern camera dial clicks exactly — one-time purchase, yours forever.

Terms of Use (EULA): https://obelisk.club/filmexposurecalculator/terms