I read somewhere about negative film having a logarithmic response similar to human vision meanwhile digital has a linear response to light. Wondering if this has anything to do with clipping in the highlights.


1 Answer 1


The clipping is different on film and digital because they work in an entirely different way.

In film, photons cause chemical reactions in molecules. Once half of the molecules have reacted, you have half as many molecules left. So as the reactions proceed, the sensitivity of the film reduces because there are fewer unreacted molecules left. So the clipping is not harsh, it's gradual.

In digital, you have a potential well where photons cause electrons to be stored. Once the well is full, it's full, it cannot accumulate charge anymore. There is no process that would reduce the capability of photons to cause electrons to be stored in that well when the number of electrons in the potential well approaches the maximum. So with digital, you have harsh clipping.

I wouldn't exactly say that film is logarithmic. It's exponential to be more precise, but the coefficient in the exponent is negative. Logarithm doesn't have a maximum, but the function f(x) = 1 - exp(-k*x) has a maximum of 1 and this function best describes the reactions that happen in a film.


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