- Depth and Depth Cues
- Monocular and Binocular Vision
And so if your inclination is to champion lost causes, the case of stereo photography is readymade for you – Paul Farber
So far we have treated the eye as if
- It were an organ capable of only two-dimensional (flat surface) vision
- We had only one of them
When we take only one eye into consideration we are said to be referring to monocular (one eye) vision.
We live in a three dimensional world – we can move in the left-right, forward-back and up-down directions. What this has given us, is an impression of depth.
Depth is a perception – a feeling of space. If we only had monocular vision, how does the mind-eye combination create this feeling? It does this with small clues that we take for granted, but use subconsciously to perceive depth.
These are called Monocular Depth Cues, some of which are as follows:
- Motion parallax
- Depth from motion
- Relative size
- Familiar size
- Aerial perspective
- Curvilinear perspective
- Texture gradient
- Lighting and shading
- Defocus blur
Depth from motion
Objects moving away reduce in size. Those moving closer increase in size. The rate of this change tells the brain how fast an object is travelling towards or away from us, and how far it is.
We have already seen that our needs to exert itself to focus. When it does this, it also sends a signal to the brain – from which our mind draws conclusions about the depth of the object we are focusing upon.
At the outer extremes of the visual field, parallel lines become curved – this distortion gives a feeling to our sense of depth just as linear perspective does. It’s our unique interpretation of the world.
All these properties contribute to adding depth to our experience of the world. Can we do better?
Yes – one of the coolest things about our eyes is that we have two of them. What does the second eye give us?
The clues provided by binocular vision are called binocular depth cues. In the following pages I’ll outline the properties of binocular depth cues.
- Vision through one eye is monocular vision. When both eyes are used the vision is called binocular vision.
- The brain uses both monocular and binocular depth cues to create a sense of space.
- Binocular vision offers us two perspectives of the same scene at the same time.
Links for further study: