Friday, November 7, 2014

The problem with edges

There is a reason why so many books on “seeing” have titles such as “Visual Perception,” Visual Thinking,” “Visual Language,” and “Visual Intelligence.” Sure, we’re dependent on the transmission of light through the eyes to the brain, but how we see is visual processing, not just image transmission. And the problem with edges has to do with how the brain processes edge information. 

Ask yourself what kind of visual information is important on daily basis. What do you need to know when walking around your house or driving down the street? Lost-and-found edges are probably not a high priority. In fact, the human brain is continually asking “what is it?” and “where is it?” We need to know where the chair in the room is so we can either sit on it or walk around it. We certainly don’t need to quantify unnecessary edge information. Vision is information processing on a need-to-know basis.

Imagine how much visual information is contained within one scene. The authors of the book “Basic Vision” did just that when they calculated an average scene viewed in shades of grey. When they also included the fact that the eye encodes roughly 30 images per second, the results showed an astonishing 3900 Mb per second per eye or six compact disks full every second. “The information flow from two eyes would fill up a 120 Gb hard drive on a PC in around 15 seconds.” And that’s without including color information.

How do we handle all this information? Image compression. This is similar to the image processing used in a digital picture when the picture is stored as a JPEG. A JPEG uses much less memory than a an uncompressed TIF image.  Information that is considered unnecessary is discarded. “The information sent back from the retina is not the raw light levels of each part of the scene but an efficient code about the changes, or edges, that are in the world.” (Basic Vision, an introduction to visual perception)

“In the visual system, regions of the image with high information content, such as edges, are signaled, but regions where nothing is changing are not." (Vision and Art, the Biology of Seeing)

If our visual system is wired to see the most obvious changes, then how do we see information that is not as obvious? The answer is simple – just look and look some more and compare, compare, compare. In this case knowledge is power and just knowing you do not necessarily see all the information should allow you to move forward and look for it.  With that said, here is some information that might be helpful.

The rounder the form, the softer the edge. The further away the object, the softer the edge. We are dealing with dimensional, atmospheric and focal information. And since we are dealing with “smoke and mirrors” in creating a three dimensional image on a two-dimensional surface, sometimes we need to exaggerate or minimize the information.

Do not assume there is an edge. Ask yourself if there is an edge, and if so, “what kind of edge?” ”What defines the form?” Is it a change in value or color or is it a change in shape. Often it's a change in information next to the form. A strong light next to a strong dark will usually result in a harder edge. Information turning into shadow will obviously not be as noticeable. A dark next to a light will appear darker than a dark in shadow. Everything is “as compared to.” Look for the doorways that allow one shape to turn into or become part of another shape. Pay attention to the edges opposite one another on an object. They should have variety and suggest dimension.

Edges are not arbitrary. They define our three-dimensional reality. They are the transition between value, shapes and color. They help to define or diminish form. Edges are areas of translation – allowing one area to become another.

“How the pieces are connected to each other is at least as important as what the pieces are.” (Gaia’s Garden by Toby Hemenway)

#painting edges