Color index is now defined as the B magnitude minus the V magnitude. So successful was the UBV system that it was extended redward with R and I filters to define standard red and near-infrared magnitudes. Since Vega is dimmer at infrared wavelengths than in visible light, infrared magnitudes are, by definition and quite artificially, brighter than their visual counterparts. The answer is called the bolometric magnitude, m bol , because total radiation was once measured with a device called a bolometer. The bolometric magnitude has been called the God's-eye view of an object's true luster.
Astrophysicists value it as the true measure of energy emission as seen from the location of Earth.
The bolometric correction tells how much brighter the bolometric magnitude is than the V magnitude. Its value is always negative, because any star or object emits at least some radiation outside the visual range. We don't know how intrinsically bright an object is until we also take its distance into account. Thus astronomers created the absolute magnitude scale. Seen from this distance, the Sun would shine at an unimpressive visual magnitude 4.85.