As for the conclusive? screen caps providing proof that Em arrives later due to sunlight and shadows, these caps are being compared as side by side proof but clearly Em is much closer to the bottom of the stairs and would therefore be somewhat darker with far less visible shadows.
Chantal is quite a bit higher on the stairs and the sunlight is able to make shadows on the wall of the stairway.
IMO These caps don't tell me conclusively which one comes first. Things can be lightened or darkened quite easily.
I can't shake the feeling that black is white and white is black.LOL