Bidirectional reflectance of dry and submerged Labsphere Spectralon plaque

We present the bidirectional reflectance of a Labsphere calibration plaque, both dry and submerged in water, at normal illumination. The measurements indicate that when submerged in water, the Labsphere calibration plaque has a higher reflectance value than when dry at viewing angles below 55 degrees . The results are presented in the form of a reflectance factor and are useful for calibrating underwater reflectance measurements.