A new model approach to the interpretation of photospheric fluctuation data is developed by calculating the attenuation coefficient corresponding to any given value of the source function using the assumption of LTE and the absorption properties of the negative hydrogen ion and the neutral hydrogen atom. Application of this method to Edmonds' recent rms fluctuation data shows it to be inconsistent with a variety of simple columnar models of photospheric structure. Various photospheric models are examined to determine the features of model photospheric structures which affect the shape of calculated rms fluctuation distributions. Finally a qualitative interpretation is suggested for the appearance of the large-scale granulation pattern toward the limb, as observed by Edmonds.