Look how sunny it was for Towner.
Wow, that looks bright. That's what you call sunny. That is, until they got to the doorway a second later.
Awh, shame. Clouds must have rolled in. But, what could blacken out the doorway? I mean: this was late November and the sun was not that high in the sky, and the light was streaming in from the west. There was nothing blocking the light from entering there. Believe me, I know because I've stood there. And we have two people who were getting so much light in their eyes, they had to visor with their hands. Look at the above doorway again. At that very moment, Black Hole Man was getting so much light in his eyes, he was visoring with both hands, and the Petite Woman was visoring with one hand. Yet here, it looks jet black.
There was shade from the top of the doorway, what Backes calls the "proscenium arch." But, that didn't cast shadow all the way down the steps. It shaded the landing but all of it. Again: think Black Hole Man. He was on the top landing, yet he was visoring with two hands.
The above isn't real. There is nothing that would have produced such blackness. It was never like that. And there is no natural spontaneous photographic reason why the picture should have come out like that. THEY BLACKENED OUT THE TOWNER DOORWAY. Why? Because Lee Harvey Oswald was in it.