Foreign Matter Effects on Cotton Color Measurement: Determination and Correction

Abstract

Literature has implied that foreign matter affects cotton reflectance and yellowness measurements made with color meters. Samples of seed cotton and lint were measured for reflectance and yellowness before and after hand cleaning of the sample faces. Results confirmed the existence of the cleaning effect on color measurements which was more pronounced with seed cotton. Because disturbance of the sample face was minimized, change in trash content appeared to be the main cause of the effect. The change in the measured area of trash in the sample face correlated well with the change in reflectance for seed cotton, but change in yellowness was less predictable. To remove the effects of trash particles on color measurements, a new method was devised in which spectrally filtered images of lint and seed cotton samples were acquired with a monochrome video camera, and a computer algorithm was written to allow color measurement on essentially lint only by not considering pixels classified as trash in the calculation of either reflectance or yellowness. Color and trash measurements were also made with a High Volume Instrument color/trash meter. Trash particles then were removed by hand from the faces of the cotton samples. Color and trash measurements were then made again with the High Volume Instrument color/trash meter. While prediction of green-red reflectance after cleaning was not improved with the new method, the blue-band reflectance of uncleaned seed cotton was more highly correlated with that of cleaned seed cotton when the new measurement technique was used. This improvement was also marginally true with lint. Additionally, prediction of blue-band reflectance of cleaned lint from that of uncleaned seed cotton was improved with the new method. Gin process-control systems requiring evaluation of seed cotton color would benefit from the use of such a technique which lessens the effects of nonlint material on color measurements.