A system for and method of assessing fluid spray using image processing techniques of a calibration and one or more as-sprayed witness cards. Calibration and as-sprayed witness cards are exposed to a backlight sufficient to make a plurality of stains thereon electronically visible. At the same time an image of the stains is captured by, e.g., a digital camera. Resulting image data is processed to assess characteristics of the stains of the fluid on the as-sprayed witness card(s) and thereby assess characteristics of the spray, e.g., volume of fluid delivered. In one embodiment, the witness card is a chemically coated semiopaque plate.