The capacity of CNF suspensions and films to transmit or scatter visible light can also give an insight into the degree of fibrillation. CNF remain intact in the suspension, having a higher light scattering, which results in more transparent CNF suspensions or films. Ultravioletvisiblespectroscopy was commonly used for both CNF suspensions [48,270,319] and films [161,318]. An imagescanner was also used for quantification of CNF filmtransparency and visualization of nonfibrillated fiber fragments[240]. Chinga-Carrasco et al. [320] compared differentoptical techniques for quantification of the degreeof fibrillation of CNF in suspensions and films, such asultraviolet-visible spectroscopy and turbidimetry, as wellas different devices, including image scanner, fiberoptic testing apparatus (FiberMaster), and a lightsourcedigital CCD camera system for dynamic measurements[320]. Although all optical techniques and deviceswere suitable for quantifying the light transmittance ofCNF suspensions and films, the image scanner was themost appropriate.