BTW, 6x4.5 "half frame" came about originally in folders -- with the inclusion of a simple drop-in or snap-in mask, the same camera could shoot full frame (contact prints big enough not to need reading glasses or magnification) or half frame (economy of more frames for the same film cost, hardly more processing). Dedicated cameras came later -- and all this professional stuff came after the folders.
Even in the original masked cameras it still meant less apparitions and vignette at the corners. Which again let you shoot more open without so much “character”.