Little story of the shot
Study your subject before you make portrait, know little bit about the person, observe.
I know it may sound funny to you but i also choose lenses to specific faces. Some faces in my eyes look better with bit wider angle lens and some less. Some fit more to studio and some to outside.
So this girl on the picture, she is friend of my daughter from school. She is coming from time to time to us to visit my kid. I always notice faces, always watch people expressions. After a year of knowing this child i said lets make her one shot. I thought to open quick studio set the lights, but then i i would loose her wildness on her face. I could scare her with all the lights. Kids don,t belong to studio, kids are free and wild. And because this shot will be just for me so i could choose where to shoot. I took her outside. I notice nice light falling on my stairs, wow that would be nice place to put her. Sun was low and behind a clouds which made amazing soft light. And now what lens would i use. I was thinking to take nikon 70-200 2.8 but, hmmmm bit to narrow. I want more of her environment and i want to be close with my lens to this child to get better connection. so i took Sigma Art 35mm 1.4 And that was a good choice. I was able to stand close and connect with her, and i was able to capture bit of environment she was in. Another thing is what angle i should shoot her from . Generally it was getting darker, Only source of light was the sky above us. Cloudy but still nice light. So i chose to shoot from slightly above .