Work flow of the image processing. Images in the center row illustrate the workflow and images on right and left the effect of noise reduction. Center row: Step 1: Two images are taken, one with illumination from the right and one with illumination from the left side. Step 2: A correction for inhomogeneous brightness is done. The diagrams illustrate the inhomogeneous brightness for which need to be corrected on the right/left image. Step 3: Images taken with either right or left illumination were combined using minimal tonal value of each pixel. Step 4: A conversion into greyscale using the red channel is done followed by thresholding. For further details see Figure 2. Left and right row: Images show the effect of noise reduction (due to droplets on the inside of the covering foil) (left and right) and an enhanced differentiation between parallel growing roots (right) after the corrections and combination of the two images.