o an artist, shadows are as real as any physical form, although these ghosts are ephemeral, changing before our eyes. There is nothing solid about them, but they define solid objects by giving them volume and weight, and create relationships between objects.
Careful observation and a little knowlege will help you understand what makes shadows look the way they do. You can then put what you see into your drawings.
Notice the shadow shapes and colors?
Why is one blue and the other yellow?
Also, why is one sharp and the other diffused?
The reasons can be explained by examining the light sources. There are two distinct sources in the images above. A window is behind, and a spot light shines from the right.
With a large light source, the penumbra gradually
fades because more and more light reaches the paper.
A small light source makes a sharper shadow.
The blue shadow is sharper. Notice its size? It is nearly actual size in relation to the object because its light source is small (a miniature spot) and far away. On the other hand, a small light up close would cast a shadow bigger than the object (think film noir). Finally, the blue shadow has a tiny penumbra making it slightly soft.
Now, let's examine the shadows colors. In my example, although you cannot see it, the sky is clear and blue, so where the spotlight is shaded, only the sky color is visible on the paper. Alternately, only the spotlight color is visible in the softer shadow. Tungsten light is warm, but not as yellow as the shadow. Yellow reflects off the objects legs, enhancing the umbra. Note that the penumbra is more neutral.
With two colored light sources, why does the paper appear white? There is no direct sunlight, so thats not it. Instead, the white paper is lit from both light sources and blue light + yellowish light = whitish light. White light is being made. But if either one of the light sources were removed (tungsten spotlight or blue sky), we would still see the paper as white. This is the result of color relativity. All colors in our environment shift warmer or cooler as the light sources change, but our eyes adjust so we still perceive the difference between colors as expected. Film and digital cameras do not have this mechanism, so to compensate, film comes in different color temperatures and digital cameras can "white balance" (i.e. daylight, indoor, etc.).
A shadow is sharpest nearest the object.
An almost black line appears below
the foot, at the point of contact.
After examning the effects of shadow on a white surface, lets look at a white object on a multi-colored surface.
It is clearly demonstrated that objects have an effect on one another with respect to color. The pencil box "takes on" the colors of things around it. If the paint on its surface was flat white instead of an eggshell finish, the color would be more even. This low gloss surface has a slight mirror effect, which produces sharper patterns of reflection, mimicking the scene around it just a bit. The image to the right has the box sitting on a green mat, which has a subtle influence on the directly lit side of the box, while the dark gray mat has a stronger influence in the shadow.
In the image above, shadows and highlighted surfaces are illuminated by green and orange. It is possible to describe these color reflections as additional light sources. There are two distince kinds of lighting demonstrated here. One is that of a light bulb generating light (which makes it powerful and dominant). The other is reflected light, which is inevitably less bright because its source is also the bulb.
In the end, it can be said that shadows are a combination of these things:
Relativity is important to understand here. What we think is a brightly illuminated white surface in one environment may match a toned shadow in another, but we may not be able to notice because our eyes automatically adjust to color cast (a predominant color influencing an entire scene, such as warm incandescent lighting or a cool ambient blue sky). Picture this crazy example:
See I told you it was silly.
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