Even if the LED is visible, is this enough to consider it consensual?

No. That would mean everyone in the world would have to be up-to-date with technological "advances", and that everyone would have the assertiveness to explicitly deny someone's attempt at filming / uphold their right to privacy. Not everyone is up-to-date, and definitely not everyone has the assertiveness, nor is there an equal balance of power between two parties. E.g., I know for sure that a lot of elder people walking in the forest would like to speak up to younger obnoxiously loud morons, but they don't because they know many people are too weak/underdeveloped/self-centered to handle criticism well, and therefore they remain silent out of fear for being physically assaulted.