In the construction of something, there are usually some distinct levels, or aspects, to them. For example, to make a painting, there is first the level of perspective and construction, whereby we provide the outline of geometrical forms occurring in a fairly abstract (but nontheless almost always Euclidian) space. In other words, the first step is quite precisely to project the 3D forms onto a 2D surface - first with the most important forms and then moving onto the details.
The next aspect is to determine the value - i.e. the way that light falls on and around the objects, the use of centre-surround, and so forth. These considerations will ensure that the eye is drawn to the objects we intend to emphasize, and more generally will mostly determine how viewers’ gazes will move around the painting. Finally, the use of color (hue) is an additional aspect which is important to reproduce both the physical reality and the emotional timbre of the subject.
And, in fact, there are still additional aspects not addressed - the level of detail used, the nature of the medium/materials used and other such considerations, all of which give meaning to a piece beyond their representation of an object in a scene.
It seems counter-intuitive, at least in the context of the arts, to make such a precise separation between these layers. This is because we think an artwork is based upon an irreducible, indivisible concept. And, indeed it is. However, the means of expressing a concept relies on certain structures and constructs. In this example, I have tried to explore how expression through art relies on the bi-modal nature of human vision.
What is this nature? That, in fact, we process images coming from the retina through two channels. One is high-resolution, only sensitive to black-and-white. The other is the colour channel which is much lower resolution. Somewhere in the brain’s processing these two channels are combined to form the imagery we see consciously.
The point is, the construction of the image can be divided along much the same lines as the perception of the image. And, for the rest of the arts, and indeed other forms of creation, taking the same approach is fruitful. It is dialectical in a sense - a conversation takes place between the persona which carries an idea, vision or sensation and the other persona which is rational, technique-oriented and who specializes in building structures.