Visual perception principles PDF

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Visual perception principles...

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Visual perception principles - Rules that we automatically apply to visual stimuli - Help to organise and interpret stimuli in consistent and meaningful ways Sensation- measurable, observable. Stimulus Perception- unobservable mental process (making meaning)

Different types of visual perception principles 1. Gestalt principles 2. Perceptual constancies 3. Depth cues

Gestalt principles Helps to construct a meaningful from (a whole, complete objects) from an array of parts or elements that when considered as isolated bits, lack of meaning “the whole is greater than the sum of its parts”  Figure-ground- perceptually separating important aspects of the visual field into The figure: objects at the centre of our focus which stands out from the The ground (background): surroundings/ all the other visual info The contour line separates figure from the ground and is always perceived as belonging to the figure  Closure- the perceptual tendency to mentally ‘close up’, fill in or ignore gapes in a visual stimulus  Similarity- involves the tendency to perceive visual stimuli or parts of stimuli that have similar features as belonging together in a unit, group or whole similar feature may include size, shape, texture, or colour (share a quality)  Proximity- also known as nearness

Tendency to perceive parts of a visual stimulus that are positioned close together as belonging together in a group Group the separate elements into a ‘whole’ based on their physical proximity

Visual constancies Perceptual constancies - The tendency to perceive a visual stimulus as remaining stable and unchanging despite any changes that may occur to the image cast on the retina Form stable, consistent understanding of what we see across time (stays the same across time)  Size- involves recognising that an object’s actual size remains the same, even though the size of the image that is cast on the retina changes  Shape- the tendency to perceive an object as maintaining its despite any change in the shape of the image cast onto the retina  Brightness- tendency to perceive an object as maintaining its level of brightness relative to its surroundings, despite the changes in the amount of light being reflected from the object onto the retina

Depth cues Sources of information from the environment (external cues) or from within out body (internal cues) that help us to perceive how far away objects are (depth &/or distance) Binocular depth cues- retinal disparity, convergence Convergence The brain detecting and interpreting depth or distance from changes in tension in the eye muscles that occur when the two eyes turn inwards to focus on objects that are close. Retinal disparity Difference in eye sight to improve depth Refers to the slight difference in the locations of the visual images one the retinas (due to different angles of view) enables us to make judgements about the distance of an objects from the viewer The two different retinal images are combined and compared

Any disparity (difference) between the 2 image provides information about the depth of the objects or its distance from the viewer Monocular depth cues 1. Accommodation Pictorial cues

2. 3. 4. 5. 6.

Linear perspective Interposition Texture gradient Relative size Height in the visual field

Accommodation - CHANGE FOCUS - The image of a large object viewed at close range will be too large to fit onto the retina - Involves the automatic focusing mechanism of the lens in the eye to adjust the shape of the lens in response to differing distances of view from the object - Those muscles are called the ciliary muscles - Information about how much the lens bulges or elongates is used by the brain to determine the depth and distance of the objects in focus Linear Perspective - RAILWAY - The apparent convergence of parallel line as they recede into the distance - Example: When looking at a road ahead the road appears to narrow. If you look to the horizon the two parallel edges of the road come together at what artists call the ‘vanishing point’ Interposition - OVERLAP - Occurs when one object partially obscures (blocks out) another - The partially obscured object is perceived as further away than the object that obscures it - Example: If a mug is placed in front of a carton of milk than we know that the mug is closer to us than the milk Pictorial cues - Information from two-dimensional image that provide information about the depth of the objects it depicts Texture Gradient

- SUNFLOWERS - The gradual diminishing of detail that occurs in surfaces as they recede into the distance, compared with objects that are close and seen in fine detail - Example: If we stand at the edge of a field of sunflowers the flowers closest to us will be seen in great detail however the flower further away will just be seen as a blur of gold and brown Relative Size. Transmission: From receptor site to the brain. - . Transmission: From receptor site to the brain. - Transmission – electrochemical neural impulses travel along specific neural pathways that connect to a specific location in the brain. - E.g. from your ears to your temporal lobe - NB. After transmission, the process of sensation is finished. However, we still don’t know what the stimulus energy we have sensed means – our brains must engage in perception. - the retina as being closer and the object that produces the smallest image on the retina as being further away - The objects being perceived must be expected to be about the same size

Height in the visual field - MOON - The location of objects in our visual field, objects that are located close to the horizon are perceived as being more distant than objects located further from the horizon - Objects looks larger the closer they are to the horizon and smaller as the move away...