Yeah I was thinking that too. No matter how tiny a capacitor, you have (tens of) millions of them on the sensor, one per photoreceptor, and you're charging and discharging them 100k-10M times per second. That's a lot of energy being accumulated and dissipated right next to the photoreceptors. Thermal noise is gonna be nuts on a modulus sensor, too.

No system is ever unbounded, period, unless you live in a world of frictionless spherical cows. At some point you run into issues caused by accuracy, energy, capacity, etc.