ILLUSION — Optical Illusions

Optical Illusions in Architecture

- The corner columns of Parthenon in the Acropolis of Athens seem to be of one width when there’s bright sky behind, though their diameters differ.

- The Columns of the Athena’s Temple in Paestum, built in the end of VI ct BC seem to be higher than for real because of optical corrections and they seem to have the same diameter in the lower and medium parts.

- Stonehenge seems to have rectangular stones but it’s just an optical illusion.

- Optical corrections make the Trinity Cathedral of the Trinity-Sergius Lavra more steady and upward-looking. Orthodox temples inside seem higher than outside. This illusion is achieved by walls bending towards the centre of the temple and by steep lines of arcs and domes. Picture: Cathedral of the Annunciation – interior.

- The Belfry of John the Great seems to be falling behind. This illusion deals with the illusory building size change when looking up.

- Campanile Giotto di Bondone is projected in laws of the reverse perspective. This technique strengthens the impression of building’s monumentality.

- The statue of Goddess Athena surrounded by the 2-floor colonnade looks like a real colossus. (Reconstruction of the Parthenon sanctuary in Athens.

- Eyes often deceive us and we see things that don’t exist. This is called optical illusions – errors of eye perception. For centuries people try to overcome them and even use. And we have to say, people are really good at this today.

Playing With Colors

Architects knew how to fix the perception errors common to a human eye even at ancient times when they built different architectural forms. Optical illusion often deals with the choice of the

observation point, features of the surrounding background or the lights. To correct the distortion masters used optical corrections at the stage of projecting of the construction. They changed the geometry purposely: changed proportions, rejected elements from its vertical or horizontal line, distorted the contours etc. On the other hand sometimes they created and strengthened optical illusions themselves. It’s thought that Greeks were the best in it as they learned to give the architectural forms plasticity and expression.

Long ago people noticed that bright objects seem bigger on dark background and the dark ones – smaller on the bright back. In optics this phenomenon is called the irradiation*. The Roman architect and engineer Mark Vitruviy (I ct. BC) described its sense this way: when combining dark and bright, the light absorbs the dark. Really, a man wearing white looks thicker than wearing black and the tree branches are much thinner in the sunlight.

Ancient Greek architects knew this illusion and used a sly move: they made the columns of their constructions of different width. The Great Parthenon for instance – the main temple of the Acropolis of Athens, built in 447-438 years BC. Its creators, architects Iktin and Kallikrates knew that the corner columns will be against the bright sky of Hellas and the rest will be against the dark background, made by the sanctuary of the temple. That’s why they made the corner columns wider and reduced the distance between them and the near columns. Thank to these corrections when you look at the temple afar, they all look the same and their difference was first noticed only after exact measurements.

The picture of Parthenon captured another optical illusion: when an eye slides over the colonnade the space taken by it stretches and the building seems larger. The same reason makes an exaggerate size of the buildings decorated with sculptures and ornaments.

Straight of Curve?

The Ancient Greek Architects knew that vertical and horizontal lines of great length seem to be non-parallel. To prevent the columns from visual split they were bended when put on the foot (Stylobate) and so the building seemed solid and strong as a monolith. To prevent the columns look concave they were made thicker in 1/3 of its height. This technique got the Greek name “entasis” meaning strain, effort. Moreover the columns were thinner at the top making them optically longer and less massive.

They fought the horizontal line sagging using another technique – line curvature. So, the stairs of the Parthenon were slightly curved and the building itself stood on a convex stone platform to compensate the illusion of floor subsidence. The horizontal beam (architrave) lying on the columns’ caps at the center part was thinner than at the edges but it looked absolutely straight from afar.

Of course not only Greeks knew these secrets. For instance the builders of Stonehenge (the most ancient stone building in England) made the surface of the stones convex in some sides. With this shape the junctions of the stone columns and the plate lying on them are optically straight (Illusion of their perpendicularity appears) and they seem rectangular.

Russian architects were aware of these illusions too. One of the examples – The Trinity Cathedral in trinity-Sergius Lavra built in 1422 over the coffin of Sergius of Radonezh. Its outer walls have appreciable slope towards the center of the building and it seems to be stable. The cylinder with cat’s windows that is the carrier of the dome is getting thinner with height. This makes the temple look higher than it really is.

There’s another illusion used in orthodox temples: it seems a lot higher inside than for real. This effect is achieved using special optical corrections. For example during the building of the Trinity Cathedral its walls above the arcs and portals and columns (pylons) were bended inward. The greater effect of height was made by steep lines of arcs and domes.

Laws of Perspective

When building the monumental constructions the architects often had to fight the imaginary distortions of their size and with change of their distance i.e. in perspective. For instance if you look at a high building from below it may seem to be much thinner on top and it’s rejected. A good example is the belfry of John the Great on the Cathedral Embody of the Moscow Kremlin, built in XVI ct. The effect of falling back is seen even on a photo; moreover it’s captured in one of the works of Giacomo Quarenghi, who painted this belfry from another point.

One of the ways to remove optical illusion dealing with perspective was suggested by a famous Italian artist of the Renaissance age, the head architect of Florence Giotto di Bondone (1267-1337). When projecting Campanile (the belfry) at the Cathedral of Santa-Maria del Fiore in Florence he made its upper part much wider than the lower one. In other words he used the reverse perspective.

Ancient Greek used another way: they tilted elements of the upper part of a construction from the vertical position. For example the fronton was established at an angle, leaning it a little front like a picture hanging in a museum. And sculptors made figures decorating the building more relief and this compensated the visual effect of its shrinking when looking from the bottom. The points of observation also were paid attention to: every statue was created considering its location in the whole composition.

Sometimes architects used the illusion of perspective not for compensation but to stress this or that visual effect. For example in a porch (a covered gallery before an entrance) the inner columns were made thinner in comparison with the outer ones making them more distant visually. This made the impression of a spacious place. Another original Greeks’ invention was that they made two-leveled inner colonnades in their temples. In Parthenon it was made first of all not for the good look but to achieve the illusion of great height of the Athena statue, standing in the sanctuary. It seemed larger near the two-leveled construction than it was and so it looked more solemnly and majestically. In one word the system of optical corrections made by architects once more demonstrates the great mastery in such complicated art of architecture.

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* Irradiation – visual perception of 3D objects and flat figures against the contrast background at which an optical illusion takes place: the observed object seems to have the wrong size.