PSY 162 Lecture Notes - Lecture 14: Retina
The Problem For the Artist
● The world is in 3-D and they want to represent it
● The canvas and the retina are 2-D
● How does the artist make a 3-D world on a 2-D canvas that can be seen by a 2-D retina
and perceived as 3-D by the viewer’s brain?
One Possibility
● Maybe the artists just paints what the retina sees?
○ Except we do not have access to a conscious retinal image
○ Perception is only available after the visual system had processed it
○ Instead, artists wanting to evoke a sense of depth might want to understand how
the brain calculates depth
Some Depth Cues…
● Can be used by the artists to create the illusion of depth
○ Occlusion
○ Perspective convergence
● Some cues against the artist and need to be manipulated
○ Stereopsis
○ Relative motion
Lighting and Depth
● When light hits a surface, different parts are illuminated differently
○ Angle
○ Light source
○ Surface properties
● An artist must learn to see actual luminance changes - not perceived depth
The Default Assumption of the Visual System
● Light comes from above
○ So circles on the left appear to be coming out
○ Circles on the right appear to be going in
○ You cannot see it any other way
● This is being processed by the colorblind where system
To Illustrate-
● Close one eye
● Put your thumb over the circle
● You will see 3 different surfaces
...Not a corner-
● Without the thumb in the way (the context) ...
To Use Shading Effectively …
● An artist must
● Learn to evaluate luminance independently of color
○ Processed unconsciously
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The world is in 3-d and they want to represent it. The canvas and the retina are 2-d. Except we do not have access to a conscious retinal image. Perception is only available after the visual system had processed it. Instead, artists wanting to evoke a sense of depth might want to understand how the brain calculates depth. Can be used by the artists to create the illusion of depth. Some cues against the artist and need to be manipulated. When light hits a surface, different parts are illuminated differently. An artist must learn to see actual luminance changes - not perceived depth. So circles on the left appear to be coming out. Circles on the right appear to be going in. You cannot see it any other way. This is being processed by the colorblind where system. Without the thumb in the way (the context) Learn to evaluate luminance independently of color.
