Post 48 –by Gautam Shah  (Lecture series: Space Perception -Article-III of 15)


The Illumination in a space is fairly consistent due the fairly steady source and predictability of the change. As one moves around a spatial field, things are perceived from different positions and in different contextual conditions. Other important factor that leads to changed perception is the increasing maturity of cognition. With the duration and proximity we learn lot more about the spatial field.

Light Corridor Hallway Shadows People Aisle View

There are many ways the eyes move. “Our eyes converge as well as diverge” according to the intensity of light and size of the field to be scanned. The fovea region in the retina of the eyes helps in perception movement. In even seemingly non-moving eyes, small jiggling movements, called micro-saccades to occur. The broadest movements occur with gestural movement of eyes and heads and shifting during postures.

Light And Shade Corridor Light Building

A spatial field has many depths.

Some fields, closer to the position of perception are illuminated with sources under our own control. Here the illumination conditions can be changed at will, or the position of perception shifted around. In both of these cases, the cause-effect has some certainty.

Bistro Dining Tables Restaurant Local Inn Table

Fields that are faraway from the position of perception are illuminated with sources under no-one’s control. Here the illumination conditions cannot be altered at will. Shifting the position of perception perhaps changes the contextual conditions, but the illumination component of the scene remains nearly static.


In very vast natural scapes the contrasts (changes) due to illumination are not highly noticed except in variable cloud cover, or during sunlight refraction at morning-evening periods.A brilliant sunrise, sunset or cloud formation in illuminated distant sky, show very little effect on the perception foreground of landscape’.


The effects of illumination are more pronounced and under control in restrictive space fields such as the built-forms, interior spaces and neighbourhood extents. Here the changes in contextual conditions accompany the changes in the foreground or components of the scene, so both seem controlled and restrained.



A spatial field is illuminated by natural light as Direct sun light, Sky Component (SC), Reflected Component (RC) of natural light, artificial illumination, and in many urban areas from surroundings’ lights like a street and vehicles. In addition to these sources, we use fluorescence to aid perception.

Fluorescence and phosphorescence are form of luminescence, or the emission of light by a substance that has absorbed light or other electromagnetic radiation.


The illuminants’ contexts are: strength and direction of source, background and foreground brightness, reflectance from surroundings, colour of light, multiplicity of sources. Other conditions include variability of space, objects and presence of dynamic (moving-vibrating) elements.

Built Space forms are occupied by objects, people and environmental effects but these rarely occur distinctly alone, in any rational form or within a nominal framing reference. The illuminants complicate the scene even if these elements manifest in for a fraction of a moment or remain unvaried for a very long period.


Single source illuminants are very definitive but complications arise due to the reflectance from many surfaces, directions, strength (brightness) and colour. Such complications are compounded with increasing number of original illuminants. Single illuminant defines a space and its objects in familiar sense, but fail as soon as the position of perception changes. Single illuminant is an irritant if any part of space has flickering movement (eg. Fan, moving curtains). Single illuminants are ideal for ‘object modelling’ as the shapes emerge without any compromises.


Perception ambiguities and compromises occur when an object or a group of overlapping objects, are lit by nearly same tonal colour value as the background. Indistinct figure-ground contrast, dissolve the edges. We tend to relate larger elements as the ground, over which smaller entities exist.

The objects are seen composition of surfaces that reflect incident light. Besides the variations caused by the angular exposition of surfaces, the surface quality or textures are detected by naked eye (at 0.07 mm). Smaller scale variations affect the gloss of the surface and mirroring effect of the surface. Very large surfaces have possibly no edges or breaks, and so are perceived through local variations of illumination.



Spatial forms are recognized with illumination references such as the proportionate extent of foreground-background, framing, strength of silhouettes, partial occlusion of elements, shading with the differing contrast and direction of the shadows, and diffusion by way of reflection, and refractions.

Stainless Design Stainless Steel Steel Building

Illuminated forms become difficult to recognize when an object curves around out of sight. Such occluding contours dissolve the edge of an object, and present poor silhouette formation. The absence of a well-defined contour renders the surface shapes (such as convex/concave) ambiguous.


The process of perception is a two-way affair. Position of a person and relative source of illumination are very important consideration for Space Planning. A person trying to project own-self must be aware of the perceiver’s distance, angles of connection, social dependency and postural condition. A strong back illumination, makes it difficult to perceive a chair-person’s features and gestures.

Concert Instrument Bass Sound Music Guitar Rock

Position of a person relative to the source of illumination also holds true in conference rooms, executive cabins, reception areas, lecture rooms, press conference rooms, etc. Natural or artificial illumination -as singular source and that too from the backside must be avoided, and if inevitable, reinforce it with lighting from other directions. One of the simplest ways is to envision how the situation manifests from every single position.

The daytime happenings, change considerably at supper time, as the ‘backbite window’ illumination is replaced with artificial lighting. Nominally the situation should stand corrected (if not reversed), but attitudes formed during daytime persist at other times. Shops in business districts are low illuminated because the staff is occupying the space for longer time and so is accustomed to low level (or even to save power), but customer entering from bright outside finds the darkness discouraging.

Side illumination eliminates many of the anomalies of perception and recognition but not all. To create good diffusion, the source for side illumination needs some depth from the occupying position. In small rooms this is rather difficult and requires careful design.


We are more used to illumination from top. But very strong such sources create under the chin shadows. This can be corrected by illumination from other directions, or from floor and table top reflections. Light colour floors and table tops, needs to be excluded from TV camera shooting angles. This is done by positioning the participants on a raised platform, and cameras at a slightly lower level then the table tops.


This is the III article (of intended 15) in series ‘Space Perception‘ that will form a course of One semester.




Post 36 -by Gautam Shah (Blog 6 in lecture series Space and Human Behaviour)


Spaces are recognized and improvised by lay persons, whereas are planned by designers, for a range of behaviour. These stack holders, though have different intentions, do arrive to some common realizations.

PixNio Image “Female sitting Library” By Debora Cartagena USCDCP

The spaces can be distinguished into several classes.

One, where the extent is endless and sometimes beyond the limits of perception, the Wild exteriors;

Two, where the marked edges define the range of perception, forming neighbourhoods;

Three, Enclosing elements creating a dimensioned spatial definition, an interior space;

Four, a threshold zone that manifests between the interior space and the neighbourhoods.

Land Markings > Pixabay Image by danilocarta Cagliari/Italia


Wild exterior spaces are recognized for the endless sensorial effects. The space is often unreal or perfunctory, as it only denotes the potential –what can one do with it? It initiates a desire to visit it, and than perhaps possess it. Visit to the place makes it real and substantial. Possession of the place is a recognition of the existing markings or implanting new ones. This is the beginning of a neighbourhood.

A very vast space is perceived through its markings. A ‘beautiful sunset, a valley or seashores’ are markings of a space. These are evident through the physical elements like: edges, banks, thresholds, slopes, plains or fences and environmental effects thereon. We perceive only certain range of space. The reach varies with each perceiver’s capacity, needs and environmental conditions so is very circumstantial.

Neighbours and their Spaces > Flickr Image by European Commission EU/ECHO/M.Morzaria


Individual markings of possessions, together form a network of bounding elements. These bounding elements identify sets of individual zones and exclusive environment available there. A distinctive neighbourhood develops due to the common territory and environment. A neighbourhood is a ‘collection of individuals and places’. As an exterior space, it is finite and predictable. Here the social contacts develop due to familiarity of people and known lay of the place.

A neighbourhood has recognizable geometric order, predictable structure, purposive nodes or anchorages, well-defined segments, distinct routes and paths, good sensorial perception and recognition of the whole and its parts.

Commercial Area of Hutong Beijing > Wikipedia-Flickr Image by Geoff McKim

 ‘A jungle of apartments where no one knew who was dead or who was celebrating what – but an archipelago of neighbourhoods, in which everyone knew each other.’ -Orhan Pamuk, Istanbul: Memories and the City.

Neighbourhood spaces have paths and open spaces that both connect as well as separate various habitable spaces. Here it is not the distance but the degree of dependence that forms unified neighbourhood space. The dependence is need-based as much as it is perception based. One may not know or formally meet the neighbour for years, or ever, but the perception someone is staying in vicinity is a great social comfort. Very often even the presence of a man-made object provides the same comfort.

Boulevard Bonne Nouvelle -ART by Eugene Galien Laloue (1854-1941)

Neighbourhood spaces separate wild exteriors from the interior spaces. A neighbourhood space comes into being and remains valid in the context of the interior space. A space created by the enclosure (interior) is far more enduring then one defined by bounding (neighbourhood). Neighbourhoods are finite, shaped and sized but spaces for inhabitation require greater degree of intervention then improvisation, and so are designed.

Interior of the Great Mosque (Ulucami) Bursa Turkey > ART by John Frederick Lewis (1805-1876)


The interior spaces are enclosed entities. The outward sensorial reach beyond the edge of the interior space does not affect either the wild or neighbourhood exterior spaces. However, other way around, Interior spaces are affected by all the happenings in exteriors. A very strong enclosure creates an isolated space, of limited relevance. However, translucency of the enclosure brings in environmental variations to the interior. The interior space and the timed environmental variations create a wide variety of purposive settings.

Olivandenhof Interior Koln > Wikipedia image by ZH2010

 The depth or scale as defined by the enclosing elements, reflecting the sensorial reach such as vision, hearing, smell, touch, etc. Interior spaces have many variegated subsections within. The major variation derives from the orientation. The degree of translucency of the enclosing elements adds several alternatives to this. Other variations are related to the use, and are specific to perception.

Inward Transgression of Exterior > Dwelling at Jaisalmer Rajasthan India > Image with Courtesy by Ms Kavita Abhijit Murugkar on FB as ( )

The enclosures of the interior spaces have varied levels of transparencies. The openings in the shell allow escapes at many places. The transgressions across the enclosure occur as outward push and inward pull of the interior space. The outward push or encroachments are often ‘cost-less’, though may ‘load’ the enclosure (shell) body. It increases the interior volume and permits a restrained exterior. The inward intrusions, however, consume interior space or estate and reduce the net enclosed space. All transgressions add extra surfaces over the enclosure body, with or without a proportional increase in volume. Both types of transgressions, inward and outward reach, make the interior spaces vibrant.

Bay Window > Outward transgression of Interior space > Amber Palace Jaipur Rajasthan India > Wikipedia Image by BazaNews

Examples of outward transgressions: Galleries, balconies, Chhatris, campanile, bay-windows, oriel-windows, dormers, Mashrabiya, verandahs, skylights, etc. Examples of inward transgressions: Cutout, Chowks, courtyards, Liwan, setbacks, cutbacks, shafts, light-wells, etc.

The form and format of an interior space are unitary and consistent, but the subsections show minor, local and temporary variations. An insulated and less affected segment, of an interior space is its core zone. A core zone is nominally centric. At the core, metaphysical elements like concepts, beliefs, taboos, etc. that reflect the essence of the inhabitation are stronger. Whereas metaphorical elements like signs, symbols flourish towards the peripheral area.

Inward Transgression of Exterior > Roman Courtyard at Vindolanda > Wikipedia image by Michael Graham

Peripheral zones become some multilateral entities reflecting the environmental variations. Where such variations become extensive and permanent, a new spatial entity comes into being. For example, cooking-dining, kitchen-bathing, entrance-living room, etc. have been one, adjunct or segregated entities, at different times or for different social reasons.

Virtual immediacy in Architecture > ART by Giovanni Battista Piranesi, Arco di Trionfo (1745-1750)

It is not necessary for the interior space and the exteriors to be concurrent in time and coexistent in space. One can conceive each, Interior or Exterior alone. Virtual immediacy of the two realms, however can be achieved by carrying across the impressions of the other. The duality of the interior and the exterior is like an antithetic zone to the other. One can also replace the physical presence of the Exterior or Interior realms through their notional representations. The interior and exteriors spaces, can occur as a ‘metaphoric concept’ for the other.

Metaphoric spaces >Wrath >  Pixabay Image by Pexels

The heaven and the hell are two surrounds of the earth. Egyptians have dummy doors (drawn or carved) in their tombs. A Garbha Griha in a temple is an inner sanctum. The Japanese gate Mori is placed anywhere, in a vast open land or sea, to mark a divide. Lakshman Rekha was a notional boundary.

Presentation of metaphoric or symbolic elements suffices to initiate a full scale happening. Pictures or names of gods on doors protect the house. Mime shows, and Bharat Natyam dance mudra enacts space through metaphors. Metaphorical declarations mark a qualitative change, and are used to compensate the territorial presence of physical and metaphysical elements.

Interior spaces are recognized for their potential for functionality (size, shape), environmental control and sensorial adequacy. Sometimes these spaces are designed to alienate the users from the expected set of things. Such diversions are used to excite, to register the change (mark of new and end of old) and also to destabilize the users.

Metamorphic > Pool of Berthesda > ART by Robert Bateman (1836-1889)


Thresholds are real or hypothetical divider marks between two very distinctive spaces and so if the distinction is dull there is no or a weak threshold. Thresholds occur at cuts and cleavages of enclosing elements of Interior space. Enclosing elements have various degrees of translucency and discontinuities where the exterior and interior have immediacy. A threshold is a place to realize both the exterior and interior concurrently, and so the thresholds are very interactive areas. The divide, presented by a threshold is not a clean edge-cut, but has a graded formation.

Graded Spaces Inside Courtyard Seville > ART by Carmen Thyssen

The thresholds are formed within the physical barriers. These barriers define the shape, size and environment of the interior space through their constitution, thickness, mass, volume, size, absorbency, transparency, etc. Other factors include the size, shape, location and orientation of the thresholds. Thresholds also have abutting structures to create intermediate climatic zone and also interpersonal space.

Threshold Zone > Pixabay Image by milldesign UK

A threshold may be an abstract divider in space or a change marker. Thresholds are marked by change in quality of flooring, illumination, sidewall configurations and by elements like high sill, steps, opening portals and pediments. Architectural attachments like verandahs, canopies, overhangs, otalas enhance the threshold’s functions. In thick-wall structures, openings get a substantial depth creating an interpersonal space as in gates and gateways, or in windows a shading device on external sides or an illumination diffuser on inside.

Thresholds and Virtual reality > Mars Effect 3 > Flickr Image by Ryan Somma

Structures abutting the threshold are like exterior transgressions and so form an intermediate climate zone and interpersonal space. Neighbours and visitors have their first encounter here, so become an ideal space for metaphoric declarations such as signs and symbols. These areas are declaration of personalized space. Metaphors take up very little or no estate, and are interpretable by only a class of people. Both of these properties are exploited in creating acutely functional and very exclusive interior spaces.

The metaphors provide exclusivity to the space and economics of expression’.


This is the SIXTH lecture in the series Space and Human Behaviour for Winter semester, 2017, at Faculty of Design, CEPT University, Ahmedabad, India.