Test were performed on an Olympus BX51 microscope with a 10X UPlanFL 0.3NA objective, comparing images produced with the RGB LED Illuminator and with an Olympus 100W transmitted light source and U-AC2 condenser. Condenser was aligned for Koehler illumination; condenser diaphragm was set to match objective NA. Camera – Canon 40D in primary image plane (without relay lens). For the tungsten light source power was set to ~90% and camera white balance was set to tungsten; for the LED illuminator (500mA driver) intensity was set to 100% for all three channels and camera white balance was set to custom with color temperature ~7000K. Exposure times were set to achieve near-full range without saturation; ISO setting in the camera - 100. Test slide was a custom slide with a pattern of squares 32μm*32μm created by metal vapor-deposition. All images were slightly color-corrected to achieve white background by linear stretch of histograms independently in each color; zero points in histograms were not changed.