Fig. 3

Example of images acquired and corresponding pixel intensity plots along a segment in the middle of the image (yellow line). The green square represents the downstream ROI, and the blue square represents the upstream ROI. A Image with a slight light pollution, resulting in a wide meniscus and decreased precision. B Typical image, at high centrifugal speed, with sharp meniscus and a steady backline, ideal for easy meniscus detection. c Image at very high speed, with a very thick sample showing very little transmitted light. The camera still detects the meniscus when the human eye cannot