This paper presents initial findings from a project that explored the use of digital cameras by preschool children in classroom science investigations. Children's science experience was viewed through a multimodal, social semiotic lens. A qualitative approach to data analysis was used to track and codify the visual choices made by the child photographers. This paper characterizes the precise visual choice-making in which the children engaged to compose their photographs. Focusing on one investigation of mixture and separation, the paper contrasts case studies of two of the focal children, arguing that a series of child-composed photographs can be viewed as a visual structuring of perceptual experience. In fact, the photographs provided visual evidence of the children's relationships to the investigation. These photographs are also compared with the children's post-investigation drawings to demonstrate differences in the use of image-as-photograph and image-as-drawing to visually characterize their roles in the science investigation.