02.02 Gestalt Theory of Visual Perception

The human eye has only a very small area where images are sharply in focus - about 3% of its central field. In practice this amounts to less than a hand's span at arm's length. So, we 'see' by building up a composite image of our surroundings; our eyes flick point to point in jumps called saccades, taking in small pieces of visual imagery at a time which our brain then puts together. When we look at a photograph or painting, the same process applies.

The spatial arrangement of visual components affect the inferences we make: concerning their relationships to each other, and how they might coalesce into a comprehensive entirety. Our eyes might capture discrete images of a trunk, leaves, roots and branches, and yet our brain recognise their relationships and present us with a 'perceptual whole' of a tree.

The way pieces of visual information or elements are 'placed' into a whole - an aspect of perceptual organisation - was studied by Gestalt (meaning "organised whole") theorists in 1920s Germany. Although some parts of Gestalt theory have not withstood scientific advance, its principles concerning visual organisation are still relevant today.

Principles of Gestalt Perception

1. The Principle of Proximity
Things which are seen together will be thought of as belonging together i.e. grouped.
Example: If a row four identical items has a larger space in the middle, it will be seen as two groups of two.

2. The Principle of Similarity
Things of which have characteristics in common will be grouped together.
Example: six alternating rows of blue and yellow balls will be seen as three groups of blue and three groups of yellow.

3. The Principle of Common Fate
Items grouped through their proximity and similarity to each other are assumed to behave as one, sharing the same fate. The eye will want them to move together, or stay put together. Anticipations of a 'Common Fate' can be used to create visual movement and visual tension.

4. The Principle of Continuity
The eye has momentum; once it is made to follow a path, it will try to continue along that same path. This principle predicts a viewer's preference for continuous figures.
Example: a sequence of points will be joined up by the eye to imply a line, or a curving line (which will induce an eye to follow it) leads the eye to an object placed beyond the end the line.

5. The Principle of Closure
The mind seeks completeness. It has a tendency to fill in missing bits of information to make a whole; to complete simple shapes. This is develops out of the Principle of Continuity.
Example: a curved line of constant radius with its ends closer together will be visually completed into a circle, or two convergent lines may have their other ends joined to complete a triangle.

6. The Principle of Area
If there are two overlapping figures, the smaller is perceived to be in the foreground, the larger the background. This idea explains how we perceive which of two objects is in the foreground (the figure) and which is the background (the ground).
Example: a net, formed of two sets of diagonal lines each at right-angles to each other, has a smaller blank oval outline in its centre. The oval will seen as the 'figure', and the net as the 'ground'.

7. The Principle of Symmetry
Areas bounded by symmetrical contours are seen as closed-whole figures, rendering the perception of symmetrical areas as 'figures' preferentially over asymmetrical ones. This principle is developed out of the Principle of Area.

8. The Principle of Segregation
For the 'figure' to be perceived from the 'ground' there must be sufficient difference between the two. This is derived from the Principle of Common Fate and the Principle of Area. Figure-ground images, like those of Escher, exploit this for their ambiguity.

These principles suggest how our mind creates groups and areas in the visual field - how each group has common properties internally, and how they might relate to other groups externally - giving rise to:

Concepts in Gestalt Perception

I - Concept of Emergence
The mind can join the dots. Groups, which alone do not contain sufficient information for the full context, can be brought together and their possible relations explored until the meaning of the whole emerges.

II - Concept of Reification
Lacking sufficient information, the mind will act to fill in the empty space. The Principle of Closure demonstrates this.

III - Concept of Multistability
Lacking sufficient information, the mind will spontaneously move between the possible interpretations. For example, an absence of enough depth cues will cause a figure-ground inversion.

IV - Concept of Invariance
Objects will still be recognised irrespective of orientation and scale.

Battistero Neoniano, Ravenna, Emilia Romagnia

Photograph Copyright ©2012 Loo Yen Yeo. All Rights Reserved.

Concept: Circles and ellipses (literal)

Description: In the realm of visual composition, implied shapes are generally considered more interesting than literal shapes. The UNESCO-listed ceiling mosaic of the Neonian (Orthodox) Baptistery in Ravenna, whose strong content - the Apostles wheeling about the medallion depicting Christ's baptism; the framing within frames of concentric circles; the bright harmonious colours; the spokes and radial sections of the periphery vectoring inward - provide the finest demonstration of an exception to a rule.

Title: Conformity

A Sunflower in Classe, Emilia Romagna

Photograph Copyright ©2012 Loo Yen Yeo. All Rights Reserved.

Concept: Circles and ellipses (implication); Single point (centre); Frame shape (non-bias patterns)

Description: Fields of sunflowers line the way from Classe back to Ravenna. This is a classic photograph where a normally static central placement of a single point, the flower's centre, lets the sunflower's pattern tell the story. Sunflowers owe their dynamic pattern to the Fibonacci sequence, which encourage the eye to trace clockwise or counter-clockwise spirals simultaneously.

Multiple concentric circles are strongly implied, and the central point of focus is accentuated by the radiation of bright yellow petals whose tapered bases vector mildly inwards.

Title: Mesmerising

03.09 Circles and ellipses

In terms of opportunities for visual composition in the natural world, circles occur less frequently than triangles. This is because the points which would imply a circle have much less freedom of position. Without the support of a curving edge or line, the composer would require:

• at least five points, because three points would be perceived as a triangle and four as a square;
• the points, and track of any curve, to be equally distant from a central point in space; and
• they would have to close enough to each other to provide perceptual closure.

Circles have an enclosing effect, tending to focus the eye inward towards their centre; therefore they are a powerful means of directing the viewer's attention into what they contain. There can also be a slight feeling movement along a circle's periphery which comes from its association with rotation.

Naturally-occurring circles include bubbles, the sun, the moon, and organisms featuring radial growth.

Ellipses, often interpreted as circles viewed at an angle, possess the same properties i.e. feeling of enclosure, and direction of attention inward to a focal point. Unlike a circle, ellipses have only two axes of symmetry and they have greater dynamism because the speed of visual flow changes - accelerating or decelerating - along its periphery.

Spring Showers on Ponte Vecchio, Florence

Photograph Copyright ©2013 Loo Yen Yeo. All Rights Reserved.

Concept: Depth (diluting depth); Perspective (tonal); Perspective (colour); Perspective (sharpness); Muted colours (contemplative)

Description: The presence of historic Florence is immediately felt due to the downplay perspectival clues.

• linear perspective - convergence of lines decreased using the zoom facility
• tonal perspective - diffused lighting lowers the difference between foreground and background contrast
• colour perspective - the lack of bright colours as worn by the pedestrians (by fortunate circumstance) and muted by lighting conditions, causes the foreground elements to recede, while the bright golden orb atop the Duomo appears to advance, compressing the viewing planes together. 
• sharpness - outlines of distant buildings are only slightly less sharp

Title: --

Tags and the 200 character limit

That's right. The first limitation I've come across in the blog is that the tag/label field has a maximum of 200 hundred characters only! Google doesn't anticipate that someone would use cross-referencing to the extent that I do.

So what's the way forward?

It's to prioritise the index/concept numbers (e.g. 01.02.3) over the concept names (e.g. Concept: frame shape). The concept numbers will be tagged as completely as possible; followed by the concepts by name, in relevance order. Not ideal, but the small 'bright side' is that the limit forces me to identify the priority order of concepts.

Orti Farnesiani's Terrace, Palatine Hill, Rome

Photograph Copyright ©2012 Loo Yen Yeo. All Rights Reserved.

Concept: Depth (strengthening depth); Perspective (aerial); Perspective (colour); Perspective (tonal); Diagonal lines

Description: Taken from a little nook on Palatino in Orti Farnesiani, this scene successfully incorporates depth-enhancing cues. Multiple interconnected planes: the garden wall on the right; the edge of a Farnesiani pavilion framing the left; the sharply-lit tree trunk; the cypress behind it; the pine in the centre; the terrace balustrade; the temples lining Via Sacra of Foro Romano beyond, and Il Vittoriano in the distance (on the left) are bathed in strong directional light

Aerial perspective (from atmospheric haze), colour perspective (warmer hues in the foreground, cooler hues in the background) and tonal perspective (higher contrast at the front, decreasing as distance increases) are at play. Viewing lines are directed in zig-zagging diagonals to the image frame, creating a feeling of dynamic energy.

Title: Hidden Terrace