reciprocity failure
Technical term in photography: the breakdown of the linear relationship between exposure time and aperture at very short or very long exposures, causing underexposure or color shifts.
In long exposures, reciprocity failure occurs, effectively reducing the film's sensitivity.
To compensate for reciprocity failure, it is necessary to extend the exposure time further.
The reciprocity law itself, which states that exposure is proportional to the product of illuminance and time. 相反則不軌 is the failure of this law.
Compound of 相反則 (reciprocity law) and 不軌 (deviation, irregularity). The term is a direct translation of the English 'reciprocity failure' used in photography.