Unnatural Lighting
Professor Alan Chalmers of the Digital Laboratory of the University of Warwick has come up with a clever idea. He points out that when we look at Roman mosaics - or any other ancient art work - we are viewing it by modern lighting and thus are not seeing it as the ancients saw it.
He is, of course, absolutely right. Today we have digital cameras which automatically make adjustments, so for the sake of digital children, let me tell you a little bit about the joys of film photography using a camera that did nothing more sophisticated than open a shutter for a certain length of time and allow light from the scene in front of the lens to fall on the sensitive film.
If you heat up a piece of iron it slowly changes colour, passing through a dull bluish shade, up to red, then orange, and finally to a pretty good white. This has given rise to the expression "colour temperature" as a means of describing the light that falls on a scene. There are special meters which can be used to measure the colour temperature and professional photographers may use filters, either on the light source or on the camera lens, to correct for the colour temperature.
The rest of us were more familiar with the effects of colour temperature on our pictures. Take a picture of your living room at midday and the colours are likely to be pretty accurate; take the same picture at night with the room lit by electric light bulbs and the colours will be very heavily yellowed. If, however, you have fluorescent lights, the colours will be very green. The effect was so marked that most film companies actually marketed a special film for use with incandescent light - with the disadvantage that if you took a picture by daylight using such film, the colours came out looking distinctly blue!
While it was possible to correct for these different lights by putting filters on the front of your lens, the photographer's nightmare was to be asked to take a daylight picture of a scene lit by fluorescent lights but with the essential features highlit with an incandescent spotlight! Unusual? Not at all: a room with a window to let in daylight, a bank of fluorescent tubes in the ceiling and a reading lamp on the desk or table and there you were, the photographer's nightmare.
Mind you, it could work out to your advantage. Many years ago I went for a late evening stroll around Jerusalem and got as far as the Kidron Valley just as the dusk became sufficiently dark for the floodlighting to cut in. Dusk is a bluish light and the floodlights, of course, were yellowish. The result was a spectacular series of photographs in which Absalom's Tomb, the Western Wall, and other sites around the Old City were lit golden against the dark blue or black of their surroundings. I use the pictures at the conclusion of my lecture on Jerusalem with the background of the song "Yerushalayim Shel Zahav" (Jerusalem City of Gold) and audiences are left with a shiver up their spines at the beauty of the images.
So, to get back to Professor Chalmers and his problem. He has come up with a bit of software which will take a picture of an ancient mosaic and light it with what he believes to have been the lighting used by its creators and owners. He boasts that his softare will help answer the problem - not a problem that I have often worried about, I must admit - of knowing how many lamps were required to light a room in ancient times.
Duncan Brown, an archaeologist employed by the Art and Heritage Department of Southampton City Council is even more enthusiastic. "It gives you a better understanding. You can model any space you want, but unless you model the light authentically, you won't see it the same way as the people who lived there."
Alas, Mr Brown may be an excellent archaeologist, but his knowledge of human perception is sadly lacking. In the first place, we have no knowledge of what light levels were considered acceptable by the owners of the mosaics. Consider a restaurant table, complete with food. In one situation it is being used to illustrate a television series by the restaurant's famous chef, in the next situation it is the scene of a romantic dinner for two. In the first situation nothing less than banks of glaring floodlights will be acceptable, in the second one or two candles will be quite sufficient!
In the same way, we may wish to be able to see the details of the beautiful mosaic and for that a minimum of 15 oil lamps are necessary; the original owner, who in any case had cluttered up the mosaic floor with half a dozen couches and tables, was quite happy with three oil lamps and being parsimonious would have preferred two except that his wife objected.
The second point is that in fact we do not see things the way Mr Chalmers' software portrays them. If your wife is wearing a white blouse, you will see it as white whether she is standing out in the sunshine or sitting in a lounge lit by artificial light. It is only if you take a photograph of her that you will notice the difference - and then you will probably complain about the change in the colours!
In other words, the human eye, linked with the image-processing power of the brain, is able to automatically adjust for a wide range of colour temperatures - a bit like modern digital cameras. No doubt the mosaic, when lit by 15 oil lamps, did indeed have an orange tinge (or, as Chalmers puts it, "a warm, sumptuous glow"!) but how did the original owners see it? The answer would appear to be that they saw red as red, white as white, blue as blue and were never aware that the colour temperature had changed.
© Kendall K. Down 2010
