The challenging and interesting thing about natural light is that it is constantly changing. And thats what makes it all the more beautiful. A picture taken from the same spot and with the same settings not only will look different at different times of the day or night for that matter, it may also just be transformed from one moment to the next. These subtle changes in lighting as the earth moves around the sun, can make a big difference to your pictures and many a times these changes can be very drastic even in a short span of time. For this reason, travel photographers at times give a lot of attention to the weather reports, and the time and position of the rising and setting sun.
It is not just the direction of the sun that varies throughout the day in relation to the subject. Its height changes the length of shadows and also changes the intensity and diffusion of light. Low in the sky, the sun’s rays are scattered by particles in the atmosphere, creating softer illumination. This effect varies significantly depending not only on the time of year but also on the latitude. The closer you are to the equator, the fewer changes there are in the lighting between the seasons, and the more steeply the sun rises. The glorious low, raking light at dawn may last only a matter of minutes and the sun sets also quite fast.
In temperate zones, lighting quality not only changes more significantly throughout the day, but is also more dependent upon the meteorological conditions. Just a little bit of cloud can have a huge impact on the lighting conditions. Being cloudy helps in reducing contrast and softens the colors; but with some situations it may be a better idea to wait for the sun to appear again. The moment you choose to take the photograph is crucial; great results often require a great deal of patience.
In addition to affecting the direction, diffusion, and intensity of the light, the time of day, the season, and the atmospheric conditions also have another important role to play. They directly affects the color of the light.
This has particular significance in digital photography because unlike with film, the camera provides a direct way of influencing the way in which this coloration is recorded. The white-balance system can be set to automatically counteract the changes in color temperature. Similarly, manual overrides can be used to enhance the red of a sunset, or to counteract the bluish cast of a cloudy day. However, these tweaks in electronic filtration can only go so far to help recreate ideal conditions, or to make up for poor ones.
Furthermore, despite all the things you can do to change images using Photoshop and other image manipulation packages, it is very hard to significantly change the look of the lighting in postproduction. White balance or digital darkroom corrections are best used to improve the natural color of the lighting, rather than to attempt to transform it completely.
The color of natural light changes because of two principal factors. First, the way in which clouds, water vapor, and particles in the atmosphere diffuse light affects some colors of the sunlight’s spectrum more than others. The reds and yellows of a spectacular sunset are caused because the purple and blue rays cannot penetrate through the atmosphere. Second, the precise color of daylight is always a mix between direct or diffuse sunlight, and reflected light bouncing off the atmosphere. Known as skylight, this reflected light is blue in color. When direct light is weaker, the visible effect of skylight is stronger—hence the bluish light on a cloudy day, or just before dawn.