In certain embodiments, determining an endoilluminator output includes calculating an illuminator contribution of an endoilluminator system and a fiber contribution of one or more optical fibers of the endoilluminator system. The endoilluminator output is determined from the illuminator contribution and the fiber contribution. The illuminator contribution may be established using calibrated or empirically determined factors, such as an illuminator leg efficiency, an attenuator factor, an initial lamp performance, and/or a lamp performance degradation factor of the lamp. The fiber contribution may be established using calibrated or empirically determined factors, such as a fiber coupling factor and/or fiber transmission ratio of the optical fibers.