Reciprocity Failure Calculator
Calculate adjusted exposure time for long exposures
About this calculator
The Reciprocity Failure Calculator helps photographers determine the correct exposure time for long exposures when film or digital sensors don't respond linearly to light. During extended exposures, the reciprocity law breaks down, causing underexposure even with mathematically correct settings. This calculator compensates for reciprocity failure by calculating the adjusted exposure time needed to achieve proper exposure, ensuring your long-exposure photographs of landscapes, astrophotography, and night scenes turn out correctly exposed.
How to use
Enter your camera's metered exposure time and select your film type or sensor characteristics. The calculator will compute the adjusted exposure time needed to compensate for reciprocity failure. Use this corrected time setting on your camera for properly exposed long-exposure photographs.
Frequently asked questions
What is reciprocity failure in photography?
Reciprocity failure occurs when film or sensors don't respond proportionally to light during long exposures, typically beyond 1-2 seconds, resulting in underexposed images.
Which films are most affected by reciprocity failure?
Color negative films and some black and white films experience significant reciprocity failure, while digital sensors have minimal reciprocity failure compared to film.
At what exposure times does reciprocity failure start?
Reciprocity failure typically begins around 1-2 seconds for most films, becoming more pronounced at exposures longer than 10 seconds or several minutes.