Representation Of Space Flashcards
How do we see?
3D space is mapped onto a 2D retina.
The eye forms an inverted image on the back of the eye (retina). This is a plastic system, e.g. glasses that turn the world upside down can be adjusted to
The eye acts as a camera, no sensation/cognition/perception
The eye suffers from…
1: spherical aberrations
E.g. astigmatism, the eye is not a perfect sphere, so certain orientations come to focus differently (some lower contrast). Can be vertical or horizontal
1:spherical aberrations
Is it possible that artists who draw elongated images are vertical astigmatics?
Anstis (2002) (x 2, objections and experiment)
An example of such artists = El Greco
Anstis made 2 objections:
Logical: the real object and the drawn picture should be equally distorted and cancel each other out
Historical: El Greco’s sketches were of normal length, were elongated only in his paintings. He painted angels as taller and thinner than mortals, suggesting deliberacy
Anstis also did an adaptation experiment, mad people astigmatic using lenses. Found they adapted after 2 days and drew images normally.
So, even if El Greco was astigmatic, he would have adapted and drew in normal proportions
The eye suffers from…
2: chromatic aberrations
Different wavelength frequencies have different energy, so bend in different amounts. Refractive power is greater for blue than red, resulting in coloured fringes
Can be exploited by artists, making colours ‘pop out’ when placed in contrast with one another
Cataracts can cause yellowing of the lens and colour vision distortion (Monet)
The eye suffers from…
3: common accommodation problems
Mypoia: blurred image
Hyperopia (long sightedness)
The eye is not a perfect optical system
To convey the retinal image captured by the eye to the brain, we need to:
Sample it (with photoreceptors), then transduce it into electrical activity to transmit it to the brain
Understanding the sampling stage can help us to…
Rationalise and appreciate how some artists exploit our visual system to achieve effects (e.g. chuck close block paintings)
The sampling stage
The retinal image is sampled by photoreceptors, each of a finite size. This poses an upper limit on the amount of detail the retina can capture, not all information will be transferred
Visual angles allow us to specify the size of the retinal image, so the amount of photoreceptors it stimulates (far away = less)
A thumb at arms length (2 degrees) is th high resolution fovea, the brain fills in the world…
Measuring resolution
As sign waves go up and down, they can change in frequency. Low - high spatial frequency
As it increases, lines become narrower and fuse into one thing in the eye
Why is resolution important?
This is important in art galleries, because there can be an optimal viewing distance for art. E.g. in pointillism (Seurat La Parade) and chuck closes block paintings (need to be at a certain distance for the nose to ‘pop out’)
Mixing colours with the optics of the eye, rather than on the canvas
Representing 3D space on a 2D canvas
Done using depth cues, which include binocular, oculomotor and monocular (one eye - movement and pictorial)
Pictorical monocular cues in particular are used by artists.
There is little the brain can do to counter their effects, because they’re grounded in the brain as stored knowledge
They include:
Occlusion Cast shadows 3D shape from shading (light from above) Relative size (smaller = further) Size constancy Texture gradient Atmospheric perspective Linear perspective Elevation
Examples of artists use of depth cues
Can play to make impossible pictures, e.g. Eschers waterfall
3D street art
Stereo-blindness could be an asset to art - art teachers often encourage students to close one eye to see depth better. Rembrandt may have been stereo-blind (stereopsis requries eye alignment)
