Painters knew it long ago: keeping the subject near the light from a (north-facing*) window is the sweetest, most flattering kind of illumination. By why should this be so? One reason is the fact that the sun travels from a point low on the south horizon in winter solstice until the summer solstice, where it reaches high above the south horizon, but always shines onto the northern sky. So a north-facing window has little or no sun directly admitted. Instead the light from the north window comes reflected from the blue dome of sky. It is indirect, diffused, and cooler in color wavelength when contrasted to the window light from the non-north windows.
But there is another reason for the magical quality of window-sourced light. Looking at the two pictures, above, the sunlight and the lens direction is very similar, taken within 5 minutes of each other. And yet the light falling on the shower curtain is so delicate and finely graduated as it grows weaker in proportion to the distance from the window source. But the outdoor photo is filled with an equally spread field of light that seems much less remarkable. In other words, when the sunlight is transformed through the window panes to act like a point source of light, then the directionality and strength is smoothly translated onto the subject. But when flooded with the same sun’s light outdoors, directionality is multi-sided and the strength of the light does not vary, thus producing less pronounced presence or awareness of defined light of a finite and particular quality.
Perhaps something similar is at play in the world of ideas, reflection, and deduction. Here, too, perhaps the sweetest light is one that is funneled through a frame to act like a single source, instead of an all-surrounding sameness. In this way the degrees of brightness can be sensed with deliberate purpose and meaning, rather than to face a uniform brightness over all surfaces, no matter the distance from that source of light. For example, an idea that is illuminated with the same light as all other subjects will not stand out with clear definition. And by shining a point-source of light on the idea, each facet stands out from the others more clearly. In other words, in the same way that window borne sunlight is often superior to the same light from the sun encountered outdoors in the open air, so too of thoughts and ideas that can be shown in best light by giving them the equivalent to window-lighting, something that is directional and with distance away from the light that corresponds with weaker light, thus adding to the perception of surface, depth, and dimensionality.
Even without drawing a figurative parallel between seeing and thinking, though, the beauty of the window-sourced light can be enjoyed in strictly visual terms alone. It benefits not only artists, but also lookers who see only with their eyes, unaided by lens or drawing instruments.
*Privileging the north-facing windows presumes the northern hemisphere. Standing in the opposite hemisphere the privileged light would be reversed: southern hemisphere and south-facing windows.