An electric filament incandescent in lamp, in particular a halogen incandent lamp (9) with a rotationally symmetrical lamp bulb (10) and I.R. radiation reflecting coating (14), has an ellipsoidal partial contour. The ellipsoidal partial contour of the lamp bulb is produced by an elliptical section, the large semiaxis, and, consequently focal axis of which is oriented vertically to the longitudinal axis, i.e. vertically to the rotational axis of the lamp bulb (10). The length of the large semiaxis (a) lies preferably in the range R