By your definition film is also digital. It too captures photons.
Photosites on a sensor capture light and then read out voltages corresponding to the amount of light captured. It's important to note they do not read out photon counts. The voltages are then quantized from continuous values into discrete ones by an analog-to-digital converter. It's at this point that the captured data becomes digital, not before.
Now in the end everything is digital. Quantum mechanics implies that space itself is like a grid, with an absolute minimum distance between any two points, rather than the smooth fabric of general relativity. But when it comes to "digital" cameras the digital part refers specifically to post-capture data quantization.
yes, the quantization of light is always digital, and that's my point. Even in your retina.
we may read voltages due to the the way they are designed, but to me this is simply a first-pass conversion of light from it's native digital to an analog expression that requires an A>D conversion downstream. But that's simply a transformation that is transformed back. The collection of photons, which is what film or a sensor do, is quite digital. That is, that the analog output is a product of how the circuit is designed. not how sensors or Nature works.
If one wishes to argue that film is more analog since it is a graded absorption in the emulsion I guess that might fly, but the sensor has a specific digital "count" for each and every photon it collects. Voltages are simply a secondary conversion, not the process of absorption within the pixel. It's just the way engineers have (to this point) designed the process, not the actual event. It is quite possible that in the future the process will become digital all the way through and A>D convertors will go the way of... emulsions.
More properly, the sensor is certainly a digital device, that reads out in an analog fashion due to design (so it does a D>A conversion by design which later needs an A>D conversion). Let's take your point; that the capture is analog until the A>D conversion. This does not follow for me since a photon hits the sensor, a digital event if ever there was one, and the information is purely digital at that point. Not sure how to see it any other way.
BTW, quantum mechanics does "respect" the plank length. This should not be confused with thinking that no other interval or system is at play. It's just the theory most consistent with what we think we know… for now… But just as surely as newtonian thinking had to be "refined" by Einsteinian Physics, QM may just be a rest stop too.
Yes, in the end, all information appears to be digital (who knew?). Thus it survives transformation. At least that's a current theory too. For a beautiful analysis of this you might have already read Wolfram's "A New Kind of Science". If you have not seen this amazing work it's something that is well worth anyone who considers themselves a Scientist should be exposed to.