I believe the term you're looking for is reciprocity failure[1] (or schwarzschild effect), though apparently it doesn't happen with digital sensors - only film.

I believe the term you're looking for is reciprocity failure[1] (or schwarzschild effect), though apparently it doesn't happen with digital sensors - only film. Noise becomes an issue in similar situations, but it's not affected by the number of photons hitting the sensor. Correction: Shot noise[2] is related to the number of photons hitting the sensor. [1] https://en.wikipedia.org/wiki/Reciprocity_(photography)#Reciprocity_failure https://en.wikipedia.org/wiki/Reciprocity_(photography)#Reci... [2] https://en.wikipedia.org/wiki/Shot_noise https://en.wikipedia.org/wiki/Shot_noise