No direct sunlight has touched any surface in this photograph.

That is worth sitting with, because the glow at the top of the frame looks exactly like sun on rock and is nothing of the kind. Sunlight enters a slot canyon through an opening that may be a metre wide and forty metres up. It strikes the upper wall, and that wall throws it onto the wall opposite, which throws what is left further down. By the time any light reaches the floor it has bounced two or three times, and every bounce strips out more of the blue and leaves more of the red that sandstone reflects best.

So the canyon is lit by its own walls. The orange is the rock's colour, multiplied by being reflected off more of the same rock, and it intensifies the deeper you look because that is where the most bounces have happened.

It also means the light changes completely within an hour, and not gradually. The glow is in a different part of the canyon at eleven than at one, and on an overcast day it is not there at all. You cannot plan this frame; you can only be standing in the right place when the geometry lines up.