But the point is the GM, at least in OSR play and in sandbox and a lot of what else is being discussed here, makes this decision based on what they think the player would know from the vantage point they have. That might be more or less generous depending on the situation. And like I said, this is such an uncontested issue at any table I have been at. If there is any question it is handled with Q&A. People are on teh same page. The GM is not out to screw anyone. The GM is simply trying to give them a 'realistic' POV of the situation. And the idea is if they can see it, they tell them what they see. Go back and look at the passages I quoted from the OS Primer again. It explains very clearly how information is obtained through interaction with the environment, and through questioning. If part of the point is to challenge player skill, you don't want to just hand them information they wouldn't have. Generally this means you won't be actively concealing things, unless there is reason for those things not to be known due to POV or a lack of interaction.