Basic composition and levers

I tend to think of simple photographic composition as balance. It is directly equivalent to a class one lever. A mass, resting directly over a fulcrum, is stable and balanced:

This is similar to the subject of a photograph being placed centrally, bang in the middle of the frame. There is no 'tension', and the results are usually dull. Occasions where it can work include where there is symmetry:

or when the subject dominates the frame:

More usually, a photograph with a single subject might have that subject placed slightly off-centre:

The introduction of a slight imbalance here adds interest. Here is a photographic equivalent:

It is worth noting that the monk is facing to the left, 'into' the frame. If he were facing the other direction - 'out' of the picture - the balance would be rather unstable. The subject here, a young monk looking through a curtain, would not justify an 'edgier' composition. The original frame was composed similarly to the finished version here, but I did play around with a few different crops anyway, each one a different interpretation of the same image. 

Placing the subject further towards the edge of the frame creates imbalance and tension. It needs justification, but can be very effective. I see this kind of skewy composition used a lot in fashion photography (especially hair and makeup), and 'hard-hitting' documentary (think blurry hands and half-faces just reaching into the edges of the frame). This diagram is it's equivalent:

This Italian farmer with his sheep is slightly composed in this way. He is offset somewhat by his flock behind him, but I was drawn to putting him at the edge of the frame when shooting. The wide lens emphasises his nose and his swarthy, rustic character, I felt, warranted the ragged and imperfect offset composition.

 

Where there are two key elements in a photograph, balance is often achieved exactly as it would be on a lever:

As you might expect, a photographic equivalent might be equally balanced and safe (and therefore potentially dull), but can also be confusing and can infuriate, where the composition uses two dominant and equal subjects. They can be hard to 'read' as one's eye darts from side to side. Consider the following:

More typically, with two elements in the frame, one would expect to see them balanced like this:

The mass on the left, although larger and heavier, is counterbalanced by the smaller weight which is further from the fulcrum. The literal equivalent, photographically, has the subject as the 'heavier mass'. The secondary point of interest fills the space on the other side of the frame. It may be (literally) smaller, simply of less interest, or, as in the examples below, may be out of focus or in the distance:

 Although it is worth striving to compose while shooting, in post-production it is easy to experiment with different crops and ratios at leisure. I should add that there is no 'right' way to compose or crop a picture, you merely choose how you feel about it.