A funny thought popped into my head. As I'm not an engineer, laugh away if this seems a laughable idea.
In the olden days of the yester year, the Minolta wireless flash system was a marvel. It metered the flash exposure real time TTL straight from the film, and was capable to order the wireless flashes to shut down when the exposure was correct. But then came the digital sensor, and everything went wrong. Now we have pre-flashes and pre-metering and many problems, which neither Minolta, KonicaMinolta or Sony have been able to correct. As I understand it, although I'm not an engineer, remember, the old system was capable to meter from the film because the film reflected light in a known measure, whereas the digital sensor does apparently not reflect it so, and that allowed the system to operate and control the flashes in real time, during the exposure.
And now the funny thought: What about the translucent mirror? Could the flash exposure be metered from it in the same manner it was metered from the film? It is after all an uniform stable plastic film, and not some multilayered surface of minuscule trinketry in constant anti-shakey shake.
Would or could that work?
Or do we start laughing?