Bill Martin's Guide to Oil Painting
Texture Helps Define What You See
TEXTURE IS MOST CLEARLY SEEN AT THE TRANSITION OF THE LIGHT TO THE SHADOW. On smooth objects the highlight is a distorted picture of the light source. The sharpness of focus of that picture defines the smoothness of the object. The glass bottle is smoother than the aluminum bottle, which in turn is smoother than the wax candle. We know this from the focus of their highlights.
On objects without a highlight the texture is most clearly seen and depicted at the transition of light and dark values.
These ten objects are arranged in the order of their degree of texture. Notice where your eye goes to determine their textures.
The transition of light to shadow is where we look to see how rough something is.
Texture in Diffused Light
Objects in DIFFUSED LIGHT seem to have LESS TEXTURE than the same object in direct light. The log and the towel appear smoother and softer in diffused light. Objects appear less textured in diffused light because their transition from light to shadow is longer.