Why Light Temperature Changes During the Day
The color of the lighting conditions changes throughout the day due to the position of the sun and the properties of the atmosphere. Air scatters blue light more strongly than red light. When the sun is lower in the sky at dawn and dusk the light passes through a thicker layer of atmosphere. This filters the blue light much more, giving redder conditions.
Before dawn and after sunset or in the shade, you get the scattered light indirectly from the air that creates the blue effect. These changes in color will be much less noticeable and dramatic during overcast days. This is because the clouds essentially mix back the light filtering of the atmosphere, resulting in even neutral light throughout the day.
Here are some lighting color temperatures to give you an idea of how the color temperature scale works in photography
Before sunrise: 10,000 degrees K
Before sunrise the only illumination comes indirectly from a blue sky. This produces a characteristic strong steel blue color.
Dawn: 2,000-2,500 degrees K
The lighting will change to a very warm red color just as the sun comes up. Look for the first appearance of shadows.
Early morning: 3,000-4,000 degrees K
The color temperature will become more neutral as the sun continues to rise through the morning.
Midday: 5,500 degrees K
Overhead sun at noon produces neutral colors, though this may not be best pictorially.
Overcast: 7,500 degrees K
Overcast lighting conditions raise the color temperature noticeably. Your photographs will have much cooler colors.
Shade: 10,000 degrees K
The color temperature in shade on a sunny day is extremely high. All of the lighting will be coming from the blue sky.
Afternoon sun: 3,000-4,000 degrees K
The color temperature will fall as the sun goes down. The light effects become warmer and redder.
