Element
To understand the mechanism of visual harmony, let’s begin by explaining some of its connected terms. We can start with the “element” of a composition – its basic constituent part. Imagine you’re standing at a comfortable distance from an object – not too close but not too far away; the intuitive spot from which you can perceive and evaluate it as a whole. From this position, your sight will only deliver a small portion of the visual field in full sharpness, but peripheral vision will allow you to comprehend the whole. The basic elements are characterised by their relative homogeneity; they border on being perceived as different. Or, to put it simply, they are those areas which are visually distinct from their surroundings. It is important to note that the surroundings are also elements themselves.

Juxtaposition
Now let’s turn to the most crucial tool in an artist’s toolbox: juxtaposition. This refers to an interaction between at least two elements to create a different effect  than that generated by either of them separately. It is an essential device of artistic expression. We have already defined harmony as a state in a painting’s composition whereby introducing any perceptible change would lead to a reduction in the aesthetic value of the whole. Juxtapositions in harmonious compositions must thus be subject to specific criteria, different from those that apply to compositions lacking in or creating only partial harmony. Why? Because we are dealing with extremes here – perfectly harmonious compositions are very difficult to improve.

Contrast – the differences in appearance
An infinite number of transformations are possible in arranging visual elements, but only one is common to all compositions. It can be described as the modification of similar relationships between elements, the level of dissimilarity, or most simply: contrast. The literature on visual perception describes many types of relationships between elements: balance, grouping, rhythm, the interplay of shapes. We will focus on the shared aspect between all these relationships, which is simply the differences in their appearance: contrast. 

Maximum contrast
In order to stimulate the senses into experiencing something, a change in stimuli is required. Differences in musical phrases or on areas of a painting can make such experiences possible. As mentioned earlier, juxtaposing two different elements creates a new effect that is unlike that created by either of them alone. This effect becomes stronger as the level of dissimilarity between those elements increases. The visual features of one component are enhanced through the disparity created by the other.

An excellent example of this phenomenon is the contrast created by a cherry adorning a cake. Imagine an image of a beige, matte pavlova topped by a much smaller, glossy, red cherry. Can this juxtaposition be any more contrasting? An apricot creates less contrast, as its surface is matte and its colour closer to that of the pavlova. A redcurrant – which is smaller and thus initially might seem to create more contrast than the cherry – simply disappears when observed from a greater distance. Similarly, if we place a diamond necklace on a grey-white chequered fabric, it will stand out less than against a black or red velvet background. A talented artist creates distinguishable forms and shapes that bring out the best of the other elements in a composition.


The level of contrast 
The eye is naturally drawn to differences, and therefore increasing the impact elements have on one another is the most straightforward – perhaps the only – way to achieve aesthetic value in painting. We’ve already established that the key relationship between compositional elements is contrast; what remains is specifying the level of contrast.

Imagine a painting that depicts, in any artistic style, sand on a beach. The multiple sand waves are all alike and rather dull to look at. Our eyes slide across the painting, stopping every now and then in places where light and shade meet on some of the monotonous ripples. Our task is to increase the expressive power of the painting by diversifying it. Let’s throw a stone in. Now our eyes immediately focus on wherever the stone is, as it stands out from its surroundings. We look at this natural object and occasionally glance at the sand. 

Here we can observe one of the much-discussed phenomena in visual perception. If we place a stone in the very middle of a rectangular painting, we will find it less appealing than if we move it slightly to the left or right. The most pleasing  positions turn out to be on the lines of the so-called golden ratio, which divides the painting in the most impactful and harmonious way. By moving the stone up or down in the same proportion, we can divide the painting in the most diverse way. The distance between the object and each edge of the frame will be completely different. This undoubtedly catches the viewer’s attention – we focus not only on the stone, but also unconsciously compare the varied sizes of the sections which were created by splitting the painting according to the golden ratio.

This is a step towards visual harmony, but our eyes do not yet perceive enough diversity to hold our attention for longer. We can thus add another stone and make sure it is distinct: bigger, smaller, or of a different colour. But even if we place it in a position where it will divide the surface in the most interesting way, all we will achieve is a slightly more compelling composition – far from accomplishing perfect harmony. We can add more and more stones of various kinds, even throw in some shells and sticks. Soon we will notice that although the painting’s structure is enriched, our eyes have become lost in and confused by the clutter of similar elements.

To stimulate our eyes to keep exploring the painting, we could add something completely different: a red sand bucket. It doesn’t matter where we place it – it is so different from the other elements that its impact mimics that created at the beginning by adding the first stone. We focus mostly on the bucket, skimming across the rest. What happened? By adding the bucket, we crossed a certain threshold. It contrasts too strongly with the rest of the composition and thus diverts our attention. It diminishes the impact of the contrasts created between all the other elements. This is a relatively common mistake in imperfect compositions.