Most likely medium format, 1620 or something, if it were full or even quarter plate we'd probably be able to see their nostril hairs. I've got glass plates from the 1890's that you can blow up any tiny 35mm size segment of and still get a perfect image, the detail can be phenomenal, nothing's ever come quite close to my eye.

Errrrm... To stop myself really getting started on cameras etc.... there's some excellent wrecked vehicle shots further down this page:
La bataille de Rânes-Fromentel

Cheers,
Adam.

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