A follower of Caravaggio, Georges de La Tour took Caravaggio's lessons on light and made something wholly new. Not apparently a likable man but nevertheless a great artist, La Tour's mature works like "The Newborn" are marvels of clear artistic thinking and execution.
In nature (except at certain times of the day-like sunset) light is never clear cut. If you were to stand in a field on an average day light tends to be diffuse (even more so on cloudy or semi-cloudy days). This is because all surfaces reflect sunlight and therefore reflected lights will deflect any strong sensations of light coming from a single source. Painters,who use light effects in their work, must rather conceive the forms before them as struck by light from a single source rather than actually observe it. This is a difficult thing for most people who are just beginning to learn painting. This is one of the reasons why "still-life" is common starting point for teaching painting. The subject doesn't move and can be lit from a single light source. The problem of light is just as acute for gifted painters like La Tour as it is for anyone beginning to learn.
La Tour's solution is to make the light source artificial, using a single candle as the source of illumination in his mature work. This has the effect of reducing all reflected light to practically nothing, only just enough to light the extreme edges of his darkest areas. Not only does La Tour reduce the light but also the colour range he uses. La Tour keeps the local colours to whites, orange-reds, red-browns, browns and touches of black placed very carefully to maximise their reflectiveness to give the effect of brightly lit and deeply shadowed areas. The brightest white is placed in the garment of the woman holding and closest to the candle. The candle is shaded by the woman's hand increasing the contrast of very light against very dark. Again using white as the local colour, the next lightest area is the hood and shawl of the baby. This gives the effect of making the areas closest to the light source the brightest. As we move further away from the light source so the local colours are made less reflective, the head-dress of the woman holding the baby is also the darkest local colour she wears. La Tour's clarity of thought about his subject and it's possibilities does not conclude here. The woman holding the baby faces the viewer and therefore receives the most light. She also wears a richly coloured but simple robe without many creases Creases in her dress would create a too great variety of tones that would destroy the effect of her being bathed in light. The woman holding the candle however is turned in profile to the viewer. Her back is directly opposite the light source and therefore becomes one of the darkest areas of the painting. She also wears a dark-coloured robe, full of creases, allowing La Tour to paint her from dark to darker without losing a sense of her roundness of form. Similarly her head-dress is dark and textured while the head-dress of the woman holding the baby is smooth.
The extremely condensed nature of the light source also makes for subtle and imaginative touches that La Tour exploits fully. By holding the candle at the level of the baby each figure and its parts are lit at slightly different levels. For example, the baby is directly lit, the head of the woman holding the candle is lit from below, the hand she shades it with from directly opposite. These minor differences of relation to the light source and the placement of figures creating many subtle variations of lighter against darker throughout the work.
It is these elements that give La Tour's mature work their ambiguity of "realism" and "other-worldliness". His mastery of technique and observation provides the "realism". The conceptual mastery of the painterly elements the "otherworldliness" .Are we looking at an "ordinary" mother or the supernatural mother of the Bible ? We can be sure of one thing we are looking at the work of a great artist.