ActinicReciprocity Failure, Offline

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.

WHAT MAKES ACTINIC DIFFERENT

• Full-stop and third-stop exposure wheel — read every equivalent exposure combination instantly.
• Sunny 16 quick-set — dial in a standard daylight reading in one tap.
• Reciprocity failure calculator — corrects long-exposure times using published manufacturer data for stocks like Tri-X, HP5 Plus, T-Max, Portra, and Acros.
• Fully offline — no camera permissions, no accounts, no network calls, ever.

PRICING

Actinic's free tier includes the full-stop exposure wheel with Sunny 16 quick-set, a reciprocity calculator with 3 built-in film stocks, and up to 3 saved camera + film presets. Actinic Pro is a one-time purchase — yours forever — that unlocks the full 12-stock reciprocity library, unlimited saved presets, and third-stop precision.

FEEDBACK

Made by a small indie team. Email obeliskclubclub@gmail.com with feedback, bug reports, or feature requests.

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