Abstract: A photographic method of collecting and reducing photographic film density data for monitoring air quality is disclosed in which photographic film is first calibrated using calibration scales of known reflectance and the measured radiance of one calibration scale step to relate the photographic film density to the known radiance. Measurement of a target's radiance and sight path radiance is made via target photographic image density analysis and mathematical expressions which convert density information into radiance and/or atmospheric transmittance data using expressions developed from the calibration scale data.