I already tried to high the contrast in Photoshop, but all i get is a sort of layered pic, that will not make a good mask :(

About the camera, i'm never sure of which settngs to apply. For this scene, i have a 200m focal distance camera. I don't know what is fine for portraits (if there is a general rule). I always work on the trial and error way, and when i get something that please me, i go for it ^^
But if there is a better way, i'm open :)

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