Clarifying the dynamics of fine roots is critical to understanding carbon and nutrient cycling in forest ecosystems. An optical scanner can potentially be used in studying fine-root dynamics in forest ecosystems. The present study examined image analysis procedures suitable for an optical scanner having a large (210 mm  297 mm) root-viewing window. We proposed a protocol for analyzing whole soil images obtained by an optical scanner that cover depths of 0–210 mm. In this study, first,we tested our protocol using six observers with different experience in studying roots. The observers obtained data from the manual digitization of sequential soil images recorded for a Bornean tropical forest according to the protocol. Second, we examined the potential tradeoff between the soil image size and accuracy of estimates of fine-root dynamics in a simple exercise. Also, we discuss implications for quantifying stand-scale fine root dynamics based on our outcomes.