Centred Composition and Symmetry
The most important feature of any photo narrative is the subject. In this case, the oak tree – being placed centrally – is clearly the main subject here.
And perhaps the most obvious compositional feature that lends its weight to defining the subject is the leading lines: (1) the top line of the fence on the left, (2) the foreground rocks running from the bottom left corner to the base of the tree, (3) hill horizon on the right, and (4) the top line of the distant hills.
These serve to draw the eye through the image into the centre.
In addition, the leading lines on the left appear to form one triangle and those on the right another triangle. Now, triangles are typically thought to create so-called dynamic tension within a scene – a sense of disequilibrium: things often seem less stable. However, I don’t think this is what’s going on in this scene. On the contrary, the central oak tree seems all the more permanent and anchored – it has stood the test of time.
There is some mirroring going on in this image but not by a repetition of the same object (which is often the case: consider, repeats of windows in a high-rise building or repeats of birds sitting on a wire). Here, the symmetry is achieved through highlight and shape. The line of mainly rectangular foreground stones catching the sunlight have their whites boosted and this serves to pick them out against the darker foreground grass. This is mirrored by the line of sheep on the sloping hill horizon whose fleeces similarly have their whites boosted as the sunlight clips their backs. Seen from this distance, the shape of the sheep could also be said to similarly generalise as rectangular. So, highlights and shape, together with leading-line triangles are the dominant means of identifying the subject of this image and creating a narrative of this object within its environment created as the eye journeys through the image.
Rule of thirds
This is, perhaps, the most well-known compositional rule. And in this image the main horizon is set close to the top horizontal third. This gives a sense of balance. And as the silhouette of the central oak tree breaks up the wide expanse of sky along this horizon, it is all the more identified as the subject.