The subconscious nature of light's effect on vision makes conscious perception of light intensity unreliable.

“So I love the way you set it up because one of the most interesting and difficult aspect of trying to educate people about light effect on subconscious vision is that it's subconscious. So we're all aware of what we think is intensity because we see the room, but if you talk to people who know how to take photographs and stuff like that, they know that the intensities varies greatly. But our system, because we have to see the same way in very bright conditions and very dim conditions, we're not very good at estimating intensity consciously. So when you try to tell people about intensity, you really struggle because they think they know intensity, but they really don't.”