Fig. 4: Extinction coefficient measurements of LSECs.

a LSEC raw intensity image normalized over the dynamic range of the camera. b Normalization to the background of the flat-field corrected intensity image. Due to interference of illuminated and scattered light, the sieve plates appear with pixel values above both background and nucleus (yellow/blue vs red/white in the used 5-ramp colormap). c Extinction coefficient map of the same LSEC. After qDPC processing, the complex phase gives access to quantitative extinction coefficients. The sample now shows values linearly increasing from the non-absorbing background to the strongly absorbing nucleus. The white encircled areas in (b) and (c) show patches of various cellular compartments (background, rim, plasma membrane/sieve plates, cell body, nucleus) that exemplify the qualitativeness or quantitativeness of the two modalities, respectively. Scale bars are 5 µm