Posts Tagged ‘luminance contrast’
What Art Can Tell Us About the Brain
Margaret S. Livingstone, Professor of Neurobiology, Harvard Medical School
I knew the keynote talk at the IEEE Visualization conference was going to be interesting when the student volunteer at the door handed me stereo glasses before the talk. The talk was focused on introducing concepts about color and luminance that artists have been using effectively for hundreds of years.
In the first part of the talk, she focused on introducing concepts such as centre-surround.
Some of the highlights from her talk are as follows:
– In some cases, color contrast is not equal to luminance contrast.
– People are good at recognizing objects from different points of view. This might be interesting since there seems to be considerable amount of work in graphics and visualization on finding the ‘best’ view for a particular dataset.
– Equiluminance – In the paper “Vernier and Displacement Thresholds in Equiluminance” by Masami Funakawa, equiluminance is introduced as follows
The notion of equiluminance is based upon the assumption that in the human visual system there are two kinds of visual pathway, i.e., luminance and chromatic pathway. An equiluminous stimulus varies in color, but not in luminance, so that it is assumed to be signaled by the chromatic system, but not by the luminance system. In psychophysical studies these stimuli are used to isolate and probe the chromatic system.
This webpage describes the use of equiluminance in art and how luminance affects our perception http://www.webexhibits.org/colorart/anuszkiewicz.html
– Depth can be conveyed using motion, shading, perspective projection, occlusion and stereopsis.
– Luminance contrast: As long as the luminance is appropriate, shape can be conveyed. She showed some interesting examples of paintings [Matisse’s The Woman in a Hat] and visual representations, where the colors were unnatural but it did not affect the perceived shape of face/object.
– Yellow, Blue and White, when used appropriately can convey motion in static images. This was demonstrated by showing some work by Akiyoshi Kitaoka’s Rotating Snakes (left image below) and Mondrian’s Broadway Boogie Woogie. It reminded me of the SIGGRAPH 2008 paper on
Self-Animating Images: Illusory Motion Using Repeated Asymmetric Patterns by Ming-Te Chi et al.
The images in this paper seem to use a similar principle and are very effective and conveying motion.
– Our central vision has high acuity whereas our peripheral vision was lower acuity. We dont seem to notice the fact that our peripheral vision has lower resolution since we move our eyes rapidly over scenes. This reminded me of the keynote from IEEE Vis 2004, where the speaker, Wilson Geisler, gave an amazing demonstration of this phenomena.
She said that Mona Lisa’s smile was particularly enigmatic since one feels her expression changing depending on whether one focuses on the eyes or the mouth. Her lab has conducted research on the same and by filtering if they have been able to create representations of how our peripheral and central vision interpret the painting, as shown here
The last part of the talk focused on the use of stereopsis by artists in making more realistic paintings. She found that many artists lack the ability to see stereopsis and that makes them see a flat world which they capture on canvas. This can be identified by looking at the glint in the eye of the photo/painting and if both the glints are not synchronized, chances are that the person lacks the ability to see stereopsis. Through her research, she found many famous artists to have misaligned eyes including the painter Rembrandt. Photographs of Babe Ruth too seemed to imply that he had misaligned eyes.
The end of the talk kept us wanting for more and I guess that implies that it was a great keynote talk.