With shading, roof surface appears to have a color variation - certain areas may appear lighter or darker - when viewed from different angles or at different times of day. Shading is generally more noticeable on dark-colored shingles because they reflect only a small amount of light, thus magnifying the slight differences in surface texture. This is a visual phenomenon that in no way affects the performance of the shingles.
Shading usually results from slight variations in texture, which normally occur during shingle production. The variations necessary to cause shading with black, or other dark colors, are so slight that they cannot be detected during the manufacturing process.
When light is reflected from a given roof, its appearance will vary as the viewer walks past the building. The impact will depend on the position of the sun and the overall light intensity. When the sun is directly overhead, the shading may disappear.
Shading is most frequently a problem in the case of black and other dark colored shingles. Since only a small amount of light is reflected from a dark surface, even the slightest differences in shingle texture may cause this problem.
In the case of white and other light colored shingles, the amount of light reflected is considerably greater. This resultsin a decrease in observable shading differences.
Blends, made of a variety of colors, tend to camouflage this effect, and make observable differences even less noticeable. Lighter blends will reduce shading more effectively than darker blends.