Now I could venture into this new wizard's Discworld or else go back to the rods and cones influence on the rule of thirds. What is the science not fable we need to know?
Hi Asher,
The big one here is that the distribution of cones (color perception) is very high near the center of our eyes (where we focus) while the distribution of rods is primarily in our peripheral vision. Rods are extremely excitable with very little discrimination (light or dark) which makes them acutely good at detecting motion (a survival skill) but very poor at resolving detail. Hence focusing upon a straight line with your peripheral vision is very difficult as the resulting image data is rather blurry.
An interesting way to test this is to go out on a dark night (or a moonlit night in a dark place) and note how as you shift from light to dark the quality of focus fades away. I first really saw this while tracking a flying heron in the dark where I could here it honking but could only see a slightly lighter blurry shape fly by at 30 feet (10 m). But simply shifting from direct moonlight (bright enough for the cones) to being shaded from the moonlight will show a strong transition in the acuteness of ones visual discrimination.
Meanwhile, the cones which have their highest density in the center of the eye (I cannot remember if the arc of sharp vision in the human eye is 2 degrees or 5 degrees) with things gradually blurring as we move away from the center of the eye.
What is important here is that
when we focus in to the thirds points in an image at a reasonable viewing distance is that
the edge of the picture frame is in our peripheral vision. This allows one to focus on the subject of the image without the image's frame interfering with our suspension of disbelief and allows us to the see the subject of an image as real rather than as a flat two-dimensional representation of reality.
Beyond that, one simply balances the body language of the subjects in an image to achieve a balanced feeling composition. Hence, the distribution of rods and cones in the eye tells us that we want to move the subject of an image away from the edges if
we wish to the subject to be viewed as the subject rather than
as an element of an image. An example of the latter could be a triptych or diptych with a single subject spread across multiple prints. There is neither a right nor wrong answer here, instead it simply takes a rule and transforms it into effects which can be used additively or subtractively to work towards the photographers narrative intent.
The big thing we get from looking at the distribution of rods and cones is that we can step away from the numbers and
start looking at how a composition feels constructively rather than following
some blind numerical mantra that prescribes a result that may not work.
This is the whole reason I call the rule of thirds idiotic. It prescribes thing for no good reason without any understanding.
Another powerful subject area that greatly influences composition is the understanding of the 3-D to 2-D transformation and how it influences perceived depth in a flat 2-D image. Consider the classic example of a fence or telephone pole sticking out about the head of a human subject and how squatting can simplify the image.
some thoughts,
Sean