If we think of the value system, as a river, and each stop along the river is a port where value was added. What was the starting point, the furthest upstream, in the value system in the film industry?

The raw materials.

Explanation:

The starting point of every manufactured object is the raw material. In the value system of the film industry, the starting point is the raw material which includes chemicals used in the manufacture of films and cameras.

Therefore, If we think of the value system, as a river, and each stop along the river is a port where value was added. The starting point, the furthest upstream, in the value system in the film industry is the raw materials.

ammonium chloride & tallow