Although the depolarized light intensity technique has been known for some decades, the time dependence of light intensity does not yet seem to be well understood. In this article, devoted to the crystallization kinetics of polyvinylidene fluoride (PVDF), we present some of the problems associated with quantitative analysis. Parameters such as incident light intensity-in combination with the detection system-and specimen thickness are shown to dramatically affect the apparent kinetics. Experiments on single spherulites grown in very thin films can help interpret the intensity-time curve. Our results demonstrate that care should be taken when comparison is made between DLI and differential scanning calorimetry.