Tuesday, April 29, 2008

Edge Induction

It was twilight in Tannersville, New York. A light rain had been coming down steadily all day. I set up my easel under a store awning because I stupidly forgot an umbrella. The aroma of French onion soup beckoned from the restaurant across the street.

The sun must have set by now because the light was failing. The light from the sky seemed to have bluish cast in contrast to the warm lights that were coming on. But I wasn't sure. I could practically feel the cones in my eyes shutting down. Honestly I could hardly see what colors I was mixing on the palette, because I forgot a flashlight, too.

As I studied the scene I realized that I could easily see the sharply defined contours of the utility pole and the roofline against the bright sky. But I couldn’t make out the clapboards or the signs; in fact I really couldn’t see the windows or doors at all—except on the bright white building in the center of the picture. So I tried to paint the scene as I saw it: blurry and tentative.

This illustrates a principle called “edge induction.” When a subject is poorly lit or in shadow, some of the edges will be below the threshold where our eyes can discern a contour. A camera might be able to pick up all the edges in these dim zones, but not the human eye.

It's not just a matter of what the rods and cones can respond to. What happens without you knowing it is that your brain takes over where your eyes leave off. In dim conditions your visual cortex starts interpolating or inventing contours based on the few edges that you truly can see and on your prior knowledge of how things should look.

The brain wants to confirm the contours first, and then it quickly fills them in with textures, tones, and colors—almost like a coloring book. This happens instantly at an unconscious level, as was demonstrated in a study published last summer by researchers at Vanderbilt University.

The visual cortex is always busy constructing a detailed fabrication of the world, whether it has all the information or not, and it tricks you into thinking you’re seeing edges that really aren’t visible.

Painters shouldn’t seek out edges that aren’t there; in fact poetry often springs from deliberately placing edges into obscurity, as Meissonier did in this portrait of Dumas.

Let edges and details go out of focus in sub-threshold or shadow areas, as Gerome did with the shadow-side eye in this portrait of a peasant. If you like a painterly handling, here’s the place to use sketchy, soft brushstrokes. It’s perfectly OK to deny the viewer the chance to scrutinize the details too much.

For more about that Vanderbilt University study and the phenomenon of edge induction, link.
The last three images came from Art Renewal Center, link.

Tomorrow is the Art by Committee sketch challenge. Please get your sketches in by Tuesday at 6:00 pm. Eastern Time, USA. To read about the challenge, link, and then scroll down.

6 comments:

Arco Scheepen said...

Again, an insightful and inspirational post. Thanks!

Erik Bongers said...

3 thoughts.
1. I love the atmosphere of that twilight zone painting. Quite impressionistic, and indeed it should stay that way. More details would ruin the effect completely.

2. When this topic poped up on my browser, the arm and head of the painting below where just visible.
I immediately reckognized it at a Sargent - I have it already in my docu folder. But the funny thing about the accidental 'cropping' on my monitor : I now saw how impressive that stretch out arm is. It really is a little masterpiece by itself !

3. (you'll want to shoot me for this one)
I noticed this topic starts like a novel. Yesterday I was browsing a number of 'writing' sites, looking for software to assemble all my ideas and snippets and scetches for stories. Things that I simply couldn't fit into a traditional text editor. As always when surfing, I got a little distracted (to this site).
Why do I mention this ?
In the article it says "...most novels written in past tense.[...]So avoid using the word 'now' because it makes the timing confusing to the reader.
It's not so much that I'm pointing my finger here - I'm just glad I remembered yesterday's lesson.
Surfin' is perhaps not a waste of time after all:)

Erik Bongers said...

Hmmm, sorry for all the typos.
Pitty you can't edit a comment in blogger.

Michael Chesley Johnson, PSA, PSNM said...

Nice piece, nice essay.

And I do love it when we artists forget some essential tool and create a beautiful painting because we are forced to "make do".

Daroo said...

Beautiful painting-- really captures the feel of the gloaming.

I'll have to read the study but it seems edge induction is related to the problem of drawing what you know instead of what you see (i.e. drawing the symbol for an eye instead of the abstract color shapes that make up the eye). Although I doubt that tendency is a function of the visual cortex.

I'd like to know your thoughts on the subjective use of edges, say as a compositional device, pushing or editing reality to add emphasis. Maybe a future post?

Victor said...

I really enjoyed the way this post was written. The first paragraphs really conveyed what your experience must have been like and made your painting even more interesting.