|Top: Sky-lit or Gray day. Left: Sun & Sky. Right: Moon & Sky.|
On a gray (or sky-lit) day the entire sky becomes a large diffused light source illuminating the landscape from the top down in a soft, gradual, nearly flat light. In these models, Reilly has assigned a local value to each picture element. The sky being the light source is the lightest at value 9. The road, locally lighter than the grass is the next lightest at value 7, followed by the grass at 6. The hillside is value 4, and the tree is also value 4. It's important to consider the gray day because this lighting helps establish the home or local values of the elements of your picture.
|Gray day value study. 2011 E. Anzini|
Sun & Sky
When the sun, a point light source, shines its light it brightens a landscape already illuminated by the sky. It creates a distinct light and shadow side to the objects. In this lighting, the tree remains the same in the shadow as it did overall on a sky-lit day at value 4. However, the sun-lit light side of the tree now jumps to value 6. Likewise, the grass illuminated by the sky was 6 overall on a skylit day, and is now value 8 in the light and 6 in the shadow. Its really important to understand that a sunny day is a skylit day with sunlight added.
|Sunny day value study. 2011 E. Anzini|
Moon & Sky
A moonlit landscape is similar to a sunny day, in that a weak point light source, the moon, lights the landscape creating light and shadow albeit with soft edges. The values of course are dampened, and the sky offers little or no secondary illumination, so the shadows go very dark.
|Moonlit value study. 2011 E. Anzini|
© John Ennis 2011
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