The quality of light
The quality of light changes throughout the day. Early morning and late afternoon sunlight has a warm colour, whereas bright sunlight in the middle of the day is much bluer. Why is this?
Scattering of the sunlight causes the change. Dust and water particles in the atmosphere reflect, refract and absorb the various wavelengths of light by differing amounts. At noon, the sun is overhead and the light travels straight down through the atmosphere. Very little scattering occurs and the sunlight is blue-white.
In the morning and evening, the sun appears low in the sky and the light has more atmosphere to travel through. The short (blue) wavelengths of light are scattered more than the longer (red) wavelengths, leading to a warmer light.
As a general rule, warm light provides more attractive images, especially for landscapes and buildings. If you are visiting places on holiday, the ideal time to capture images is in the early morning, soon after sunrise. Not only will the light be right, but there will be fewer people around.