I’m not sure where you’d even start for brightness. On a single-photon scale being picky about wavelength(which definitely can do) starts to shade into being picky about energy, but if there’s a way you could could scale that to help you with bulk photons(especially if you didn’t want to completely constrain the supported colors; but even if you were OK with that) I have no idea what it would be.
There are materials whose transparency is modified by photochemical or thermal effects, like self-darkening sunglasses; but even if you are OK with the refresh rate that’s not quantizing, just throwing a variable amount of attenuation at the incoming analog signal and getting a less intense analog result.
