"The structure of an object is its form...
the structure of the material from which it is made is its texture"
- Michael Freeman in 'The Photographer's Eye'Texture arises from the representation of similar elements countless in number, at a minute size relative to the overall size of the image. Texture is thus a function of scale: think of the ears of wheat in an image of an extensive wheat field. A defining characteristic of texture is that should appeal most to our kinesthesia - our sense of touch - despite being observed via our visual sense,
Surface texture is observed clearest when illuminated by directional lighting at an acute angle: the smoother or finer the texture (i.e. the larger the scale), the more acute the incident light required to emphasise the relief*. The limit of this approach is reached when the surface is so smooth as to be reflective, in which case no angle of incidence and produce shadow contrast.
*Relief is a sculptural technique where a raised 'figure' is created by carving away the 'ground' or background. The clarity of the figure relies on the creation of shadow contrast, created by incident light, to give it definition (see Relief).