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.

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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 47  –by Gautam Shah   (Lecture series: Space Perception’ -Article-II of 15).



One of the most important functions of architectural openings is the composition of vision. And the fascinating aspect of the visual makeup, inward or outward, is the stratification of the view. The stratification is circumstantial, intentional or accidental.

Corridoio_vasariano,_veduta_di_ponte_vecchio_01The view of outside or inside gains different dimension depending on how far or close, one is from the picture plane (face of the opening), what is covered within the nominal cone of vision, and the postural-gestural movements of the head and body to scan the view. Architectonic elements also mask, frame and filter the view.



Regular architectural openings, and incidental ones like the crevices or holes, are effective when the surfaces like wall or roof are very extensive. Openings arouse curiosity to discover the realm on the other side. Windows, can be enlarged or reduced in size to regulate the scope of vision, but doors cannot be modified due to the basic anthropometric requirements. For visual makeup openings are transgressed outward and inward, through the floor or roof.


Low Level Window


Window in glass floor

The mechanics of vision depend on several factors, such as: a vision cones, extent of the framing element, sill and lintel level, shading devices, depth of opening, design or configuration, quality of glazing, level of maintenance, differences of illumination between outside and inside, amount of the glare, treatments on internal and external faces of openings, quality of external surroundings, internal reflections, tasks, orientation, climatic conditions, illumination conditions, need for protection and privacy, etc.

The visual makeup also depends on the position of the viewer.


Visual scope and depth of openings: A viewer deep inside, away from the opening, gets a nominal straight or horizontal view. But as one comes closer, the scope of vision increases. The visual makeup is surmounted by architectural elements like overhangs, horizontal fins, the sill height, height of the opening in comparison to eye level (in supine-sitting-or standing position) and depth of opening.


Visual scope for clerestory openings: For a person positioned close to the plane of opening, if the sill level is above eye level, the range of visual scope is small. This scope becomes larger as one moves away from the plane of opening.

Bed Bed Room Home Sky Lights House Room Modern



Visual scope and the datum of floor: Tall buildings (multi-storeyed) have several floors, each of which offers different vistas. For a person positioned, approximately as deep as the internal height of the floor, the visual-scape is nearly horizontal. So at lower floor one sees street and surrounding activities, from mid floors the view consists of horizon consisting of tree or building tops, but on upper floors the view is of the horizon. In the second and third categories, at night additional flickering brightness from bottom up sources is very distractive, such as from the head light beams of moving vehicles, street lights, road-light signals, illumination or glow from hoardings and neighbouring buildings. These reflections fall on the ceilings and sometimes on the wall, but distort the interior visual effects.

looking down


● Surrounds of the openings, all four sides, jambs, sills, or bottom of the door-heads, alter the inward and outward vision scope. The sloped surfaces due to chamferring on the outward or inward faces, enlarged the perceptive size of the opening. It however made the perception depth ambiguous due to the foreshortening.


Downward View Tracy_Caldwell_Dyson_in_Cupola_ISS

● The dividers or sub elements of openings, such as traceries, mullions, muntins, are primarily used as mid support in the frame or sash, and divide the glazing into smaller units. Early age glazing units were small but had fuzzy transparency and wavy patterns of making. These crude smaller units, however divided the view and made it bearable.



● Openings in moving vehicles offer dynamic scenery, where the objects could be both, stationary as well as moving. Uniformly shaped and sized objects, in nearby visual range seem more dynamic, but variegated objects in distance, seem to be less moving. These two fields when viewed through separated horizontal sections of an opening, pose distinctly different scenes. Such experiences are more common in carriages with additional windows at higher level.

Slit openings

● Stratification is very important issue with openings of fixed glazing and shop front windows, both of which serve the function of a picture window that frames a scene or to displayed items.


● Fixed glazing windows show a scene consisting of several layers depending on the point of observation and floor datum. These layers, typically at lower section consist of ground level shrubs and movement of people and vehicles. At mid level the scene consists of mid-portion of trees (effects of breeze-wind) and perhaps deeper vista. At higher level, (the top lite) mainly sky and upper sections of very tall buildings (becoming impersonal due to greater inclination-distance) are seen. Of the three, the change is more pronounced at the lower section, and often curtained of with ‘parlour curtains’.

485028169_373693d56d_zShop front windows reflect the opposite side scene, in mainly two distinct strata. Upper part, if shadowed by solar inclination or overhang, has little reflection, but lower section has strong reflection (called ‘bounce-back’). Reflections at lower section do not allow view inside, unless interior portions have additional illumination.


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