Original Shot -- Making it Digital. First the shot’s scanned frame by frame (24 frames per second-20 sec. shot), then each frame is stored as an individual full-color image with a resolution of 2,048 by 1,556 pixels.
Rotoscoping : Artist at a computer outlines frame by frame the portion of original shot that’ll be used in the final version -- in this case, a portion of the field and several of the running soldiers.
FINAL STEP, Compositing the different components (rotoscoped foreground, water, town, people in the town, boats, cannon fire, smoke, explosion, birds flying overhead,etc.) LAYER BY LAYER to create the final shot as it appears in the movie. Once digitally composited, the shot is “written back” to film so that it can be spliced into the movie