This is of particular importance in such areas as telemedicine. The ability of a display to show true flesh tones depends in large part on the colorimetry of the display. TV phosphors have been fine-tuned for decades to provide the most natural skin tones possible, and, although not yet widely used, are unchanged in some FEDs. FEDs are CRTs in disguise. Thus, one drawback of FEDs is that the vacuum tubes do require maintenance.
Electrons stream from the cathode to the anode to illuminate phosphor.
FED technology provides a wide color gamut with continuous dimming and 8-bit gray scale. Unlike CRTs, FEDs have no cathode heater, no deflection system, and no shadow mask. FED technology is so new that although many medical display manufacturers have purchased sample quantities, only a few have incorporated them into devices. Raising the anode voltage to obtain greater phosphor efficiency requires increasing the stand-off distance between anode and cathode to prevent arcing. The natural emission angle of the electrons produces a spot size that is too large, so this stream must be focused.