The substrate is the key distinction: heading 3701 covers sensitized flat plates and film made of non-paper, non-paperboard, non-textile materials (typically plastic or glass base), while heading 3703 covers sensitized media whose base is paper, paperboard, or a textile. A resin-coated photographic paper falls under 3703; a polyester-base film sheet falls under 3701.

The subheadings 370320 (color) and 370390 (non-color) carry separate tariff lines with potentially different duty rates. Importers should verify the applicable rate for each subheading at the time of entry, as the color designation is determined by the emulsion type rather than the intended end use.