A method of operating a display comprising a plurality of active pixels for displaying an image, the active pixels each including a drive transistor and an organic light emitting diode (OLED), a first reference pixel including a drive transistor and an OLED, wherein the first reference pixel is not part of said plurality of active pixels that display an image, a second reference pixel including a drive transistor and an OLED, wherein the second reference pixel is not part of said plurality of active pixels that display an image, a memory and a controller coupled to the plurality of active pixels, the method comprising: operating the first and second reference pixels under a first and second predetermined stress condition, respectively, the first predetermined stress condition being different from the second predetermined stress condition; determining a first characterization correlation curve based on electrical and optical characteristics determined from the first reference pixel operating under the first predetermined stress condition; determining a second characterization correlation curve based on electrical and optical characteristics from the second reference pixel operating under the second predetermined stress condition; storing, in the memory the first characterization correlation curve for the first predetermined stress condition and the second characterization correlation curve for the second predetermined stress condition, each of the first and second characterization correlation curves providing a quantifiable relationship between the optical degradation and the electrical aging for the first and second reference pixels operating under the first and second predetermined stress conditions respectively; determining, by the controller, a stress condition of an active pixel , the stress condition falling between the first and second predetermined stress conditions; and determining a compensation factor to apply to a programming voltage for the active pixel based on the determined stress condition and the first and second characterization correlation curves of the first and second stress conditions; wherein the first and second reference pixels are placed under different stress conditions via different current levels. operating the first and second reference pixels under a first and second predetermined stress condition, respectively, the first predetermined stress condition being different from the second predetermined stress condition; determining a first characterization correlation curve based on electrical and optical characteristics determined from the first reference pixel operating under the first predetermined stress condition; determining a second characterization correlation curve based on electrical and optical characteristics from the second reference pixel operating under the second predetermined stress condition; storing, in the memory the first characterization correlation curve for the first predetermined stress condition and the second characterization correlation curve for the second predetermined stress condition, each of the first and second characterization correlation curves providing a quantifiable relationship between the optical degradation and the electrical aging for the first and second reference pixels operating under the first and second predetermined stress conditions respectively; determining, by the controller, a stress condition of an active pixel , the stress condition falling between the first and second predetermined stress conditions; and determining a compensation factor to apply to a programming voltage for the active pixel based on the determined stress condition and the first and second characterization correlation curves of the first and second stress conditions; wherein the first and second reference pixels are placed under different stress conditions via different current levels. <EOS>