In order to characterize the image for fade due to light, it can be exposed to a very high intensity light source, with the following conversion of the exposure to real time. A care must be taken to match the spectrum of the expected light exposure to that of the light source used in accelerated test. Thus, the fraction of ultraviolet component in the light source must be carefully adjusted.
When the test is designed to simulate the exposure to sunlight (either direct, or filtered through the window glass), it is common to use Xenon Arc light source with appropriate UV filters. In a fade machine, the samples are mounted in a lantern arrangement around the central Xe-Arc source, and then constantly rotated to equalize the exposure.
Alternatively, the samples can be exposed to light real-time in areas where the sun exposure is very high. If appropriate controls are put in test, relative performance of different systems can be compared this way.