Thanks very much, super super helpful! First time posting in this community and am delighted to received such a detailed and kind response. Thank you.
With this background, I can now go on to research waveforms and digital cameras and their log systems without being even more confused!
Since this post is about understanding film response to light, I looked into exactly why film responds logarithmically, but couldn't find an answer, I can only speculate, for anyone who might be interested, or offer better insight, I've written my thoughts, as I noticed there aren't many threads about this online:
It might be to do with the fact that silver halides, once exposed to photons (unit of light) that reduce them to pure silver specks (which form the latent image), cannot 'record' another photon exposure, so with increasing number of photons, there is a decreasing probablilties of hitting another silver halide, so film response slows down, because there is less and less material to be exposed with increasing exposure. Or maybe its because when a photon hits a silver halide, it splits the silver and halide, ejecting an electron which needs to travel and find a silver ion (a silver atom with a missing electron) to attach to, before turning it into a pure silver atom, if it doesn't find one in time, it might return to form the silver halide it originally was a part of. Maybe with increasing exposure, increased number of ejected electron flying about, something happens to the probability of finding silver ions, because there are also equally more silver halide bits for the electrons to return to, spread out across the crystal lattice. Or maybe its to do with development. Developers turn the remaining unexposed silver halides into pure silver specifically in areas with already reduced silver (silver specks formed by exposure), in a way amplifying the latent image. But developers work faster in areas with more silver specks, slower in areas of less silver specks, this makes sense, areas with more silver specks have more exposure so need to be developed more. But are they developed in proportion to the original speck amount? As developer reduces silver halides, there will be increasingly more pure silver, maybe causing exponentially faster developing. But with areas of less silver, developers may take a long time to accumulate enough silver to increase development rate. This suggests that the development phase is not linear either. I might be really wrong about this, and would need a scientist to expalin this properly, but essentially, all this put together might somewhat explain why film doesn't just count photon by photon like a digital sensor does, and it's good enough for me :)