Mary Ellen Mark is one of my favorite photographers.
My understanding is that she started with a Leica rangefinder, which she used for years, suplemented that with Nikon FM2s (manual camera with high fill flash sync speed) for her India pictures. Moved to a Hasselblad and finally to a 4x5 Linholf Technica. In some photo mag article she was quoted as saying that for interior 4x5 she uses a big studio flash that allows her to shoot at f32. She shoots Tri-x in all formats. She still uses all three formats today.
I like her earlier work best, since her current exterior people shots, particularly the medium format ones seem heavily fill flashed.
Tom