Here are three pictures I want you to look at. They were taken on Via Piccolomini, only a few streets away from the hotel we stayed at in Rome.
The first photo was taken as I was walking towards St. Peter's cupola on Via Piccolomini. The further away you are from the cupola the larger it appears. The others were taken from the fence at the end of Via Piccolomini. In the second photo I used the zoom lens to get a closer view of the cupola. The 3rd photo was taken as it was.
I did not realize when I took the photos that it was an optical illusion. I was taking a walk early one of the first mornings and happen to have my camera. A few days later Giuseppina mentioned that her cab driver had mentioned this optical illusion as he was taking her to the hotel. I went back to look at my pictures and sure enough, the cupola looks larger on the pictures I took further away from it.
This is also a YouTube link where someone shot a video of it. Next time I'm in Rome, I will have to take my own video of it, and in the daytime.
http://www.youtube.com/watch?v=hpviV1ehsgc
I showed these photos and the YouTube video to my students yesterday, and I had underestimated what an impact it made on them, so I wanted to share it with you too.
If you have any photos from this street, do share them with me.
I feel that the optical illusion is a phenomenon similar to when we see the moon on the horizon and it looks HUGE, then as it travels higher on the sky, it appears smaller. It is still the same moon. Here the cupola appears large as it is the only thing seen against the horizon of the street. As one gets closer and sees the broader horizon, the cupola is no longer isolated, and it is seen at its actual size. Any other theories you may have, please share them, inquiring minds need to know.
A friend sent me the following information: I found a website that explains this sort of optical illusion. It shows some exercises that explains optical illusions such as this one. The cupola is like the circles. The circles are the same size but their position to the circles surrounding them makes them appear larger/smaller. Check out this web page:
http://www.visualillusion.net/Chap04/Page04.php
On the other hand, the moon changes in size because the bend of the horizon. The bend of the horizon magnifies it or makes it smaller depending its position in the sky relative to us. So the harvest moon isn't an optical illusion, the horizon acts like a magnifying glass; the light that shines from the moon bends with the atmosphere making it larger. Thank you Jennifer.
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