That's a very nice photo portrait. I can't comment on the canteen/flask, but will be interested to learn with you. An interesting thing that I see is the stand behind the soldier. We can see the three legged floor stand behind him. The vertical rod is hidden behind his leg and body, but we can see just a little of the yoke that is bracing the back of his head and holding it still for the long exposure. It's visible just under his left ear. It was effective here, too. Note that his head and shoes are in very crisp focus, but most every other part of him shows VERY slightly softened edges, because he moved ever so slightly. His breathing probably caused that.