Hemoglobin (HGB) measurement results for six different patients’ whole blood samples, using lens-free on-chip imaging, are compared to the results of a commercially available hematology analyzer (Model Coulter LH750, Beckman Coulter). Average light intensity collected from ~18 000 pixels of each lens-free image showed a good fit to the Beer–Lambert model,14 yielding a maximum error of ~2.9%, compared to the hematology analyzer. The top-right inset illustrates the experimental apparatus, which uses a cuvette (8.9 mm thick) containing hemolyzed RBCs under 420 nm illumination.