Starch-based films are promising alternatives to synthetic films in food packaging. They were widely studied in terms of mechanical and optical properties. In food packaging, optical properties are of great interest because ultra violet (UV-light) protection is strictly required. Nevertheless, the characterization of film-forming dispersions was poorly addressed, especially regarding its correlation with the film produced. In this work, we characterized film-forming dispersions at different compositions of starch and carboxymethyl cellulose (CMC) by Turbiscan. This instrument is based on multiple light scattering and gives significant information about the miscibility of polymers in the dispersed phase. Indeed, it identifies the phenomena of destabilization and phase separation before their visibility to the unaided eye. This work aimed to study whether the homogeneous/inhomogeneous morphology of films could be forecast by the analysis of profiles obtained in the dispersed phase. The films produced were investigated by optical microscopy and absorbance analysis. As the CMC fraction increased, Turbiscan showed reduced phase separation. This implies better miscibility of mixture components and higher gelification degree. The related film was more homogeneous and presented higher UV absorbance. Consequently, film-forming dispersions and optical properties of films are strictly correlated and Turbiscan-based analysis is very useful to investigate the dispersion stability and predict the film quality.