http://camera-obscura.co.uk/camera_obscura/camera_obscura.asp
The next time I go to Edinburgh I will definately be visiting the Camera Obscura.
Text and pictures from Camera Obscura website:
HOW DOES IT WORK?
The mechanics of the Camera Obscura are a cross between a giant pinhole camera and a periscope. At the top of the tower is a dark chamber with a mirror on top which reflects light downwards, passing through three lenses before projecting a stunning image of the city onto a large white table. Your guide turns and tilts the mirror to give a 360° tour of Edinburgh while giving a fascinating and fun commentary. Don’t miss the chance to pick up a passer-by in your hand in this amazing interactive exhibit.
In the centre of the Obscura room is a white painted, concave wooden table. 21 feet 4 inches (6.52 metres) above it is a 10 inch diameter glass doublet lens. A metal cylinder rises another 6 feet 9 inches (2.06 metres) upwards with a singlet lens halfway and a triplet lens 5 inches in diameter at the top. The cylinder projects out of the roof of the Camera Obscura and is covered by a protective hood, open to one side. Under the hood facing out through the opening is a plain mirror protected by a pane of ordinary glass.
The light from any object passes through the glass. The mirror is set at an angle and so reflects the light downwards, through the lens and on to the white table, where an image of the object is visible when the room is darkened. The mirror tilts and rotates to change the view.
The image is not magnified but is reproduced at life size. It is also correctly orientated. In a basic pinhole Camera Obscura the image is upside down and reversed. In this Camera Obscura the mirror and lens turn the image the correct way up. The lenses of course also focus the image. The focus is very precise and the depth of field (area from near the lens to far away in sharp focus) is also very large. This is achieved by having a very small aperture, equal here to F67. The F number is simply the focal length divided by the diameter of the lens. (Focal length is the distance from table to lens. The focal length is 337.7 inches. The top lens is 5 inches in diameter. 337.7 divided by 5 is equal to an F number of 67.54).
If the aperture became smaller still, very close objects would also be sharply focused. But then this would cut out more light, and make the image too dark. With the present 5 inch lens most of the picture is in focus and the image on a reasonable day is bright enough. The large depth of field avoids the need to constantly adjust the focus.
The distances involved in the Camera Obscura are huge when compared to those in a photographic camera. This creates another problem. The lenses focus light in a curve. To overcome this, the table has a concave surface to match the curve of the focus. Nevertheless the image is still less clear at the edge than it is in the centre. This is due to the fact that any lens is weaker at the edge. With an image of this large scale the weakness is clearly visible.
The quality of the image is however excellent. This is due to the present lens system which was installed in 1947 by Barr and Stroud, the Glasgow firm of scientific instrument makers. Apparently in 1853 the image was smaller and less clear than it is today.
| CAMERA OBSCURA ON TV, FILM AND LITERATURE | |
| Camera obscuras have appeared in literature and films, here are some examples: | |
| This is Edinburgh, 1961 by Miroslav Sasek is a guidebook about Edinburgh, in which he talks about the Camera Obscura. Here is an excerpt: As we start down the Royal Mile, which runs though the Old Town from the Castle to Holyrood Palace, we stop for a look at Edinburgh in the Camera Obscura. It’s no Magic, it’s “nature’s TV”, a kind of periscope. |
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| 'Secret Knowledge' by David Hockney For two years, British Artist David Hockney investigated the painting techniques of the old masters, and like any admirable sleuth, compiled substantial evidence to support his revolutionary theory. Secret Knowledge is the fruit of this labour, an exhaustive treatise in pictures revealing clues that some of the world's most famous painters, Ingres, Velázquez, Caravaggio (just to mention a few) utilized optics and lenses in creating their masterpieces. |
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| Vermeer's Camera by Philip Steadman Philip Steadman's remarkable book Vermeer's Camera cracks an artistic enigma that has haunted art history for centuries. Over the years, artists and art historians have marveled at the extraordinary visual realism of the paintings of the 17th-century Dutch painter Jan Vermeer. The painter's spectacular View of Delft, painted around 1661, and the beautiful domestic interior The Music Lesson seem almost photographic in their incredible detail and precise perspective. Since the 19th century, experts have speculated that Vermeer used a camera obscura. However, conclusive proof was never discovered, until now. In Vermeer's Camera, Steadman proves that Vermeer did indeed use a camera obscura to complete his greatest canvases. |
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| The wonderful 1946 British movie ‘A Matter of Life and Death’ (British title) or ‘Stairway to Heaven’ (US title) features
a scene inside a camera obscura. It is a fantasy story of a British
flyer, played by David Niven, who refuses to die after falling in love
with an American WAC (Women’s Auxiliary Corps) during his last moments
of life. A beautifully conceived scene in a camera obscura between the
WAC and an English doctor is short but effective. You can find it on
DVD or in a revival of old movies and it is a delight on many levels. |
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| The Underground Man by Mick Jackson,
Penguin, 1998, is a novel about a real 19th century eccentric, the Duke
of Portland. In one of the later chapters of the book he visits the
Camera Obscura in Edinburgh. Here is a passage from the book: Like my co-spectators I rested my hands on a circular railing and looked down on a broad concave table-perfectly smooth and white – whilst the woman in tweed pressed on with her practiced intonation about the room in which we stood. With one hand she had told of a long wooden rod which hung down from the high ceiling and as our eyes accustomed themselves to the dark she gradually became more visible. Her hands and face had about them a ghostly luminosity. She twisted the rod, saying, ‘… the same principle as the camera. A tiny aperture in the roof allows an image to be cast on the dish below…’ |
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| Girl with a Pearl Earring by Tracy Chevalier, Dutton, 1999 This is a novel about a young girl who works as a maid in the household of the painter Vermeer. The novel includes a scene with a camera obscura. This is a delightful book and well worth reading. |
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| The Secrets of the Camera Obscura, a Novella by David Knowles. Chronicle Books, San Francisco, California, 1994 A strange mystery set in a camera obscura. Here is an extract from the book: …in the centre of the room rests a circular screen, three and half feet in diameter, which acts as the focal point for light that enters the chamber from a kind of periscope in the ceiling. The whole thing is done with mirrors. What you get is the live image of the outside world, the cliffs to the north, the ocean, and the windmills in the park… This article is adapted from one on Jack & Beverly Wilgus’s website: http://brightbytes.com. Theirs is the best website on camera obscuras that we know of. | |
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