Whilst the first connotation most make with the word filter is a face effect, we looked more carefully at the audience and as they would be more likely to capture with their back camera than take selfies, a world facing effect would be more suiting. I say this as it shows that having an AR developer/designer/creator onboard from concept stage can make all the difference, rather than only bringing someone on last minute to execute an idea planned without the prior involvement. The most effective experiences I have seen have been those which bring on skilled AR experts early on in the process.
The result is a well received and shared project (with a magic glow when the environment gets darker).