In a recent thread on an SCA group on Facebook, a number of people discussed modern sources of light that could be disguised as period, including LED "candles" complete with flicker. My contribution was to mention my wife's policy of trying to always get the dinner dishes washed before it gets dark. It occurs to me that this raises a more general issue: What are the reasons for authenticity of various sorts in the SCA or similar contexts?
One reason, and the one that the commenters pretty clearly had in mind, is to avoid damaging the ambiance, the appearance of a medieval environment, for other people. That consideration gives us the ten foot rule, the idea that everything should look period if seen from at least ten feet away. It also gives part of the requirement for participation in my encampment at Pennsic—nothing that is both obviously and unnecessarily out of period.
Fake candles, coolers concealed in chests, cameras built into something that looks period, all solve the problem of damaging the ambiance for other people but not the problem of maintaining the ambiance for the people who are using them. It's harder to imagine that you are a medieval person when you are turning on your candle by pushing a button and not worrying about whether it is too close to things that might burn, or when you are putting ice in your cooler or photographing a battle. If what you are doing poses no problem for other people, other people have no reason to object to it. But it still poses a problem for you, which is a reason why you might choose not to do it—in order to enhance your own experience.
A further reason to prefer the real medieval solution to the modern solution disguised as medieval is suggested by my wife's policy. Medieval people faced a different set of constraints than we do, and one of the differences is that they had no easy way of producing good artificial lighting. By imposing that constraint on ourselves we put ourselves in something closer to their world and give ourselves a push into figuring out how they dealt with it.
By, for instance, arranging to do anything that requires good lighting in daylight.