Tuesday, April 5, 2011

See-Through Square

Here’s a fun experiment. Cut out a square of bright colored paper about two or three inches across.

Hold the square about four inches from your eyes. Let some light shine on the side of the square you’re looking at, so that the color appears vibrant. Now, keeping both eyes open, look off to a scene in the distance.

You may notice that the square appears transparent in the middle but opaque at the edges. Here’s the effect simulated in Photoshop.

The reason, according to vision scientist Dr. Margaret Livingstone of Harvard, is that our color receptors respond to color borders, but they tend to disregard flat, homogenous areas of color.

Our color system codes a color area by establishing its color contrast at the edges of the area, and then fills in perceptually. Even though a tomato is colored red equally at its edges and at its center, we only get information about its color from the edges. We don’t  get any direct information from the red in the center at all.

The color spills into the center of a form from the edges, an effect called "color assimilation."

The phenomenon is also illustrated by the “watercolor illusion” by Lothar Spillmann, where colors along the border of a shape seem to leak into the shape, and we perceive a tint of color throughout the shape, even if it’s not really there.

In our experiment with the colored squares, the information from the far-seeing eye takes over where the near-seeing eye is getting no data, giving preference to the scene. At the edges of the square, the color border information from the near-seeing eye takes precedence, making the square seem opaque.
“Watercolor illusion” Lothar Spillman on Journal of Vision
Vision and Art: The Biology of Seeing by Margaret Livingstone


Hawk Richards said...

Is that not the something as when you hold your hand/arm 8 inchs to a foot from your face. When you do that it seems like you can see right through it but you still see the edges of your hand. I don't think it has to be a bright colored peace of paper.

Unknown said...

Hi James,

I have read about many different optical illusions, and while it is fascinating learning about them, they leave me wondering how to apply that knowledge to actual painting... What is your take on that? Do you ever get to apply any such specifics to your painting. Thanks so much for posting such informative posts, your blog is a painting encyclopedia :)

James Gurney said...

Hawk, I think you're right--it will also work for a dark piece of paper or any flat shape, but color perception is especially coarse it works especially well with this trick.

Dalibor, good question, and I've been wondering that, too. The first thing I thought of was the graphic device of putting a light colored line next to a black line, as David Lance Goines does on his posters: http://www.tbfa.com/ebay/goines/cp_red.html

But I'm not sure how to apply it to traditional painting. Should we be aware that edges are more important than middles? What happens if you neutralize the center of a bright colored form? I'm not sure what to take from this either, but it's cool to know how our eyes work.

Steve said...

I'm taking a studio painting class this term and our instructor happened to cite Livingstone's book yesterday, Vision and Art. It seems one possible painting take-away from knowing the primancy our visual system confers to reading edges is that we can use warm background colors (which generally bring objects forward) and still have them seem to recede if we carefully construct our edges and negative shapes in such a way that overlap and scale changes bring the desired objects forward. In other words, the predominance of of our minds' edge-reading can override factors of temperature in paint.

Scorchfield said...

Another dimension of ilusion:

Piranesi 3D

Anthony VanArsdale said...

Now this is an interesting post.
I recently finished two paintings where the highlights and shadows were very similar, but one had more chroma in the transition from light to dark. It looks from a distance that one is warmer overall, as if the highlights are borrowing from the more vibrant edge. I wonder if the same thing here applies to those paintings.

Roberto said...

Jim- These visual illusions are always very interesting to me. I can never see any of the bi-ocular illusions because I can only see with one eye (I do have some peripheral vision in my bad eye which helps with depth perception), but I like learning about them and how they influence other's perceptions.
The “watercolor illusion” effect is a fun graphic trick used in poster art, as you point out. I think both of these illusions are used by sign painters all the time (intentionally or not). The importance of edges is particularly evident when executing very large signs and graphics. Most of these projects are on very uneven surfaces, and executed by a team working very fast and very up close. After the piece is completed there is usually a final touch-up pass made over the whole image, in order to fix little mistakes or drips, or to clean up lines etc. It is always amazing to me how much of all these little errors, which are quite visible up close hanging on the wall, yet can’t be seen from just a few feet away on the ground; And the ones that are seen are usually around the perimeter, or where there are edges.

@Scorchfield- Thanks for the trip,Man! That’s some pretty good stuff. Let’s get this guy to do one on Escher! -RQ

Mark Heng said...

That "putting a light colored line next to a black line" trick reminded me of some of the paintings of Wayne Thiebaud. Sometimes his cast shadows have a saturated colored line around them which seem to give them a strange energy...

This is very exciting, the discussion of artistic devices used to simulate subjective perception, like your insights on bluish hazy night pictures.

Roberto said...

While we’re on the topic of bi-ocular experiments, visual centers in the brain, consciousness, Zombies and eye-scanning… I thought you might find this article interesting -RQ

Engineering & Science Fall 2010


(Article: Be Aware of Your Inner Zombies, page 14.)

I followed up on Scorchfield’s 'Piranesi 3d' link to find out more about the creators of the video, they are Factum Arte. Check this stuff out, these folks are at the cutting edge! Enjoy. -RQ

Lyndon said...

Neat. I just tried this with a flyer that has a lot of blue background. As I shifted to where the extra-bold white writing is, I got 'opacity' along all the colour boundaries, changing a little as the visual system adjusts to movements of the card.

In my design course they had us read (pretty sure this was the book) Johannes Itten's The Art of Colour, which I recall is quite big on thing slike boundary effects. Though yeah, not certain what you do with that information if you're not at the Bauhaus.

Roberto said...

oops. Factum Arte: