The invention pertains to an exposure apparatus, a method for controlling a photosensitive element to radiation using the exposure apparatus, and a method for exposing a photosensitive element to radiation. The exposure apparatus includes a base assembly having an exposure bed that supports the photosensitive element, and a lamp housing assembly having two or more lamps. The lamp housing assembly includes an adjustable ballast connected to at least one of the lamps to adjust power received by the one lamp, a sensor for measuring irradiance impinging the exposure bed; and a controller that adjusts the adjustable ballast based on comparison of the measured irradiance to the target irradiance, thereby adjusting the irradiance emitting from the lamp to the target irradiance.