Getting to the Point
It is a curious revelation to consider that in every point of space that we perceive in our surroundings, light is passing through that point from all directions. These are particles of light – photons – that emerge from light sources or are scattered/reflected from a surface on which light is incident.
This is perhaps a highly abstract thought, but it is one very much centred on the reality of the nature of light. So in gazing across an illuminated room, there are an infinite number of discrete points through which light is travelling – each with a unique and characteristic spatial and spectral identity at any moment in time. Unless, however, we interrupt the light beam in some way we cannot observe the presence of light at any these co-ordinates. Thus to see an image with our eyes, we have to capture those photons upon our retinas. Likewise using conventional film in a camera, the photons give up their identity within the film emulsion or camera chip. Light also has the key property of non-interaction – so that one beam of light can pass through another beam of light with no mutual interaction and is the underlying principle which lets all visual senses operate.
What we see with our eye is some finite end point of vision in terms of photons which can be identified with unique points of travel to our own visual apparatus on the retina. The conventional two dimensional ‘camera obscura’ is acting to resolve vision to stark simplicity where light from a small finite fraction of the total quantity passing through an effective point can be observed in glorious simplistic detail. Most of what we really see is in turn perceived via a relatively small area of the retina – that of the macula.
In an interior environment, the attributes of the light are determined by the relative complexity of possible sources of light and reflecting surfaces. In Nature, there presents scope for an almost totally bewildering complexity. By learning, for example, of the true spatial nature of light in a natural context, we could more readily simulate this in interior environments.
Virtual Bubbles
We can, however, give a clearer idea of this ‘point’ identity concept using photography as an analogy. We can for example imagine a small virtual sphere or ‘bubble’ and attribute wavelength and frequency of occurrence to photons that pass through the centre of the sphere and emerge from an ‘exit’ point on the ‘bubble’ surface. This only describes the light emerging from one specific ‘point’ of light. This is like describing a ‘magic’ camera where the light spreads out from a central point in all directions and is detected by a sphere which can in turn record the spectral distribution of light at any point on its inner surface.
Does this represent a fundamental measurement parameter of light? If so can we then use new and emergent technologies to capture such information as a more faithful representation of our visual spaces? As a physical representation of the nature of light this would amount to a relatively large amount of information for any specific co-ordinate point.
Photography has been developed to emulate as closely as possible our own human visual systems. There is no doubt that the simplest approach to measuring this ‘point of light’ quality is to use photographic techniques to conveniently integrate up the visual information. The strength of photography is its inherent resolution of physical dimension. Its weak point if any, is the translation of spectral distribution of photons to brightness/colour of the resulting image at any specific point. We can think instead perhaps of the slowest digital camera in the world which scans the spectral distribution and stores this data – for each point on the surface of a virtual sphere associated with a point of light – rather than using a grain of film to respond to the complex spectral input or the CCD element of or a red/green/blue element to integrate and derive an appropriate signal value.
Light – Natural and Unnatural
We can see that if we take a room with (clockwise) red, green, blue and white walls, and illuminated with a central light source, we are going to get variation in this point definition of colour in space. If we look at the blue wall, then we are not aware that behind us is the red wall sending a complex field of scattered light to the blue wall and from which some photons will in turn be reflected back to us. We would instead get a better description of the spatial content of colour if we could sample a ‘point of light’ somewhere in the centre of the room.
How great are the differences at an absolute level between ‘artificial’ and ‘natural’ image spaces in terms of absolute spectral distributions across virtual point source spheres? These are perhaps greater than we think. This however, is an absolute question, not in the first instance one about the simple visual appearance of things as interpreted by our own visual system or by photography. We probably need to use technology to go to the level before the one where we perceive images as the result of integration of signal.
We can just as easily relate this observation to the natural world. Again, it is the perceived image that the eye registers, of landscape, with perhaps an ever changing vista of sky, land and water in changes by the second, minute, hour, day, and season, so that again the quality of light is always changing in a subtle way, but one which nevertheless can be readily contemplated.
Mind Games
Why indeed bother with this line of investigation? Perhaps it is curiosity on the notion that there is something fundamental awaiting to be discovered about the inherent perception of the total ‘quality’ of light in an environment, rather than just its flat 2D image that we use.
It may be therefore, that not only is the eye/retina/visual cortex processing images of the real world in ‘real time’ at marvellous resolution, but it is also in the background undertaking gradient measurement of relative distributions across the retina at levels which do not normally register visual differences and triggering associated responses.
Investigation may bear out some surprises and these, for example, could have relevance for architectural/lighting design and indeed across many aspects of behavioural patterns. Vision systems of other creatures may be specifically sensitivity to subtle aspects of light quality.
In Conclusion
The reality therefore is that the quality of light is not simple, except perhaps in the laser laboratory where you really do know where the light is coming from.
