This change in color from summer to autumn occurs because of the
ever-changing angle of the earth relative to the sun and what happens to
the light rays as they diffuse through the atmosphere at a more obtuse
angle. In the winter, the sunlight must actually pass through more atmo
-
sphere to reach the ground than it does in the summer. This is because
the hemisphere (Northern in June and Southern in December) is tilted
toward the sun in summer, making the light rays reach the earth at an
acute angle, making the sun appear higher in the sky, and letting the
sunlight take the most direct route through the atmosphere. In winter,
the hemisphere is tilted away from the sun, making the sun appear
lower in the sky and causing the light rays to reach the hemisphere at a
lower, more obtuse angle. In this case, sunlight takes a longer path
through the atmosphere.
Regardless of the calendar month or hemisphere, winter sunlight is
always closer to the horizon than summer sunlight, resulting in a lower
average angle in winter and a higher average angle in summer. Spring
and autumn light are phases between summer and winter, so the light
source will be somewhere in between the extremes of summer sunlight
and winter sunlight. If you plan on lighting a scene within one of the
polar regions, perhaps it’s best to go to the library and start studying
geography!
Note: Lest we confuse any readers, be it known that summer
starts in June in the Northern Hemisphere and in December in the
Southern Hemisphere.
Time of year may be a subtle consideration. It may not matter at all in
many cases, but in some cases, illustrating the season can make the dif
-
ference, giving the shot a temporal anchor. Snowy winter lighting is,
after all, quite drastically different from sunny summer lighting.
Atmospheric Conditions
Not every day is sunny and clear. Changes in the weather make a dra
-
matic difference in the way your scene is lit.
······························Chapter 2: What, Where, When?
27
Take, for example, a clear sunny day and contrast that with a cloudy or
rainy day. Sunny days have a hard, bright, warm main or key source (the
sun), complemented by a diffuse, cool secondary or fill source (the sky).
On rainy days, however, the key source is usually the clouds — most
likely a grayscale diffuse source.
Part I: Lighting Theory ···································
28
Figure 2.6: A cloudy day. Note the soft shadows and low contrast.
Figure 2.5: A sunny day. Note the hard shadows and high contrast.

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