A simple and effective film reciprocity calculator for photographers. Select a film type and metered exposure time - the calculator will provide a reciprocity compensated exposure time. The app includes an exposure timer so you can time your long exposures. You can also use a slider to adjust exposure when you have filters attached.
The app supports a wide range of film stocks and allows the user to enter their own times for reciprocity failure.
You may need to setup Reciprocity Timer in Settings -> Notification Center to ensure the app's timer can notify you when exposures are ending and your device is asleep.