Cognitive Daily

We’ve been in Rome for a few days now, and we’ve seen several wonderful examples of how Renaissance and Baroque artists were beginning to re-learn the lessons of perspective, which, if 20-year-old memory of art history class serves me, had been discarded during the medieval period while artists focused on the social and religious dimensions of art.

Realistic perspective in paintings requires artists to understand a lot about the human vision system. If you can accurately portray perspective, you might just be able to build a jumbo-sized cathedral on a moderate-sized budget.

The most ambitious attempt at this I’ve ever seen must be the church of Sant’Ignazio di Loyola of Rome. Looking at this detail from the church’s ceiling, you almost believe that it ascends to infinity:


Unfortunately, the illusion only works from one point in the church. Once you start to move around, the illusion breaks down. Take a look at this view from under the church’s “dome”:


The formerly “straight” column is now awkwardly bent, revealing the artist’s clever deception. The ceiling of the church is actually nearly flat.

But the church designers saved big bucks with this design: a few painters are always cheaper than legions of stoneworkers and masons.

An even more impressive illusion was achieved in the Palazzo Spada, where the architect Francesco Borromini designed a columned passage to appear 35 meters long when it was in fact just 8 meters in length:


The floor of the hallway slopes upward, and the ceiling and walls converge. Even the “hedges” at the end of the hall are miniaturized, as is the sculpture in the center. Unfortunately the museum didn’t let visitors walk up the hallway for action photos, so I had to generate this picture from a postcard after the fact.

My physics is a little rusty, so I’d hardly be able to venture a guess as to how tall Nora would appear next to the sculpture. Any estimates from readers? Nora is five feet tall in real life.


  1. #1 Aaron Couch
    June 13, 2007

    That hallway by Borromini is fascinating! The technique is actually called Trompe-l’œil or “trick the eye”. In light of Friday’s “Is science art?” post, I think this certainly proves that it can be. According to a couple of web sites, the sculpture is only 60cm tall (1.95 feet). Assuming the sculpture itself represents a 5 foot tall person, Nora would appear to be almost 13 feet tall!

    I found a photo of someone standing at the end of the hallway. The quality is a little poor, but you can see that the woman at the end of the hall now appears to be quite enormous:

    Unfortunately, I never got to visit either of these locations when I was in Rome two weeks ago. I’ll keep this in mind if I get to go back someday.

  2. #2 Dave Munger
    June 13, 2007

    You spoiled all the fun 😉

    I wanted people to figure it out from first principles….

  3. #3 Rick
    June 13, 2007

    I get 21 ft, 10.5 in.

  4. #4 Dave Munger
    June 13, 2007

    Wow, Rick! If that’s true, then we’d only see up to her waist in the picture. Either that or Aaron’s estimate of the size of the sculpture is wrong.

  5. #5 roseindigo
    June 13, 2007

    When many of those ceilings were painted artists actually had to learn to DISTORT the perspective of the human body, so that when viewed from below there would be enough compensation in the proportions for the human form to look normal. I suppose the same could be said for columns and other objects. If they had painted the correct proportions everything would have looked distorted from below. Can’t imagine that sort of genius it takes to get that right.

  6. #6 Tony Jeremiah
    June 13, 2007

    Probably mathematical reasoning alone cannot tell you how tall a person will appear in the context of this illusion, given that illusions have a psychological/perceptual component.

    In this instance, one would have to take into consideration the principle of size constancy (e.g.,,
    which tells us that our brain is pretty good at judging the size of objects despite differences in how far they are away. For example, a seven foot person standing 100m away is likely to be perceived as being taller than a 5 foot person standing 1m away.

    In a picture, however, if you cut out the actual image of a 7 foot person in the “background” (i.e., 100m away) and place them beside the 5 ft person, the 7 ft person will look like a tiny elf next to the 5 ft person–mostly owing to change in perceived distance but not retinal image size.

    So to answer the question accurately, one would likely have to take into consideration size constancy, as well as retinal image, actual size of all objects near the primary object of focus, actual distance of objects, person’s knowledge of actual size of objects, and several other perceptual aspects involving the interpretation of visual scenes.

  7. #7 Warren
    June 15, 2007

    I think Rick’s right. If the hall is 8m long but meant to resemble 35m, that means the end must be roughly in quarter scale (4 * 8 = 32). That means a 5′ tall person would appear to be about 4x in size at the far end, or roughly 20′.

  8. #8 Jude
    June 22, 2007

    I am painting this particular one at the end of my hall, going into my master bedroom. Is there any way or do you know of a book that has it’s step by step instructions? I did one in my dining room, with instructions. I have been an artist for 22 years. Can y’all help me?
    Respectfully, Jude

  9. #9 Justin
    June 27, 2007

    Here are some more examples of anamorphic illusions, done as chalk drawings on the ground. Pretty cool technique!

  10. #10 anonymous
    June 28, 2007

    ignazio.. at 9 gigapixels..

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