The law of reciprocity in the digital age is invalid.

It should be noted that the photosensitive characteristics of electronic image sensors (CCD and CMOS) are different from those of film, so the failure of reciprocity law needs to be reconsidered in digital cameras, and the experience of film cameras cannot be simply applied. Moreover, image sensors with different production processes have different performances on this issue, and the experience of one camera cannot be applied to another camera.

Since the digital camera can play back the just-shot photos through the LCD immediately after shooting, and check whether the exposure is as expected, it can generally get more accurate exposure through simple tests even without accurate metering and without considering the problem of reciprocity law. Therefore, the law of reciprocity and its failure can be ignored in the era of digital photography. However, another problem needs careful consideration-signal-to-noise ratio. When the light is strong, the noise signal of the image sensor (noise, manifested as noise and contrast reduction) is covered by the strong light signal, which is not easy to affect the imaging. When the light is weak, the problem of signal-to-noise ratio becomes prominent. Moreover, the working time lasts for a long time, the temperature will gradually increase, and the noise will increase geometrically, which is the most troublesome problem for long-term exposure of digital cameras.

Taking some heat dissipation measures to control the temperature rise of cameras, especially image sensors, is the best way to deal with the problem of signal-to-noise ratio decline.