An optimal lighting is necessary in order to recognize alterations and smallest lesions during the endoscopy. It is not only a problem of the light power. The Celvin number of the light limits the recognition of the color. The resolution power will be reduced when the lighting is too high or too low. It would be desirable to have light generators which always produce the same lighting independent of the distance between the tip of the endoscope and the object. There is no danger for the patient because of the high temperatures in the light generators.