Light Teaserin Academic
By deleted141154/deleted (3,942)
on September 11, 2005 6:55:33 AM CDT
Photography literally means writing with light. There is no more succinct description of what underlies the art of photography. Yet the fact is that many, if not most photographers never learn what are light's natural properties, and how subtle alterations in those will affect the picture's impact on its viewers. Anywhere you find light, it will have these five intrinsic elements: direction, volume, contrast, size, and color temperature. Some of these properties are obvious to naive observer, while others are masked by our brain's autonomous mechanisms. I will explore each individual characteristic, and illustrate its potential power to influence how its audience receives an image.
To prepare you to engage light on its own terms, let's start with its two most intuitively understood properties- direction and volume.
Direction behaves exactly as it sounds, as light emanates from a source, it travels outward from that source in all directions in straight lines. You can almost always decipher where the source of light is by looking at the shadow objects cast. The light source is always on the opposite side of an object from its shadow. The direction of light falling on an object is intuitively understood by the viewer, and must be carefully considered by the photographer before making an exposure. One example of the strength and subtlety of the direction of light on our perception is how normal overhead lit scenes look, and how awful things look when lit from below, think- summer camp ghost stories and flashlights held up under someone's chin.
Volume of light is simply the amount of light measurable at a point in space. It is the absolute intensity of light; beyond precise scientific measurement, the photographer can assess the scene and instantly know if it is dark, or bright. How much light is available will dictate which parts of the scene can be rendered within film's light sensitivity range. Ultimately, the challenge is to know how much light there is present, and to operate the camera such as to allow proper exposure of the recording media, be it film, or digital. If there is a lot of light present, more of the scene can be captured; as opposed to there being little light present, where more of the image will necessarily fall into darkness. Volume is closely tied to another of light's properties- contrast.
While not immediately perceptible to the untrained eye, contrast is something photographers can learn to read quite easily. Contrast is a ratio of the volume of light measured at any two points. The word contrast automatically means that you have two places you are comparing against each other; in our case, comparing how bright each is. As light it spreads out over space, the farther it travels from its source the dimmer it gets. Simply put, light gets twice as weak every time you double the distance from the source. That means that any scene lit with even one light will have a range of contrast present; again, because light becomes weaker the farther it is from the source. How much contrast there is in a scene strongly influences how we interpret it. Strong contrasts in light lend the scene drama and intensity; conversely, lower contrast brings with it a calmer mood, a more intimate setting, and a feeling of quietude. Daylight desert scenes, images made during high noon, and ones made by the light of a candle, or a fire, are almost always high contrast. Overcast days, foggy conditions, areas where the overhead lights are very evenly distributed, or spaces with strong lighting and lots of bright surfaces tend to show low light contrast. With practice, lighting contrasts can be closely estimated with a trained eye.
Another characteristic of light that can be seen with the naked eye, once we are taught to look for it, is the relative size of the light source. The light source's size relative to the object's size plays a critical role in the quality of shadow the object casts. Small light sources, like the sun, cast very sharp shadows. In our usage, sharp describes a sudden transition from light to dark. The sun is considered a small light source, because its apparent size relative to the size of a person. I can hold my hand up and block out the sun, it's tiny. Indirect daylight entering thru a window is a good example of a large light source, the window's overall opening is probably several feet by several more feet. It's not easy to block it out with your thumb is it? Large lights cause objects to cast soft shadows. A shadow is described as being soft when it slowly gradates from light to dark without a definitive boundary. The correlation between the relative sizes of object and light source is another key element in controlling the mood in a scene. Sharp shadows tend to heighten drama, whereas soft creeping shadows, those were the shadow slowly fades around an object's shape, tend to lend a mellower mood. Imagine a lone man standing under an even lonelier streetlight, his eye sockets sharply outlined in deep shadow; that lone bare bulb light source is an awfully small light source, the shadows it casts on our suspect also casts shadows into our imagination. Then imagine light streaming into a north facing window, you are inside, the walls all freshly painted snow white, there is hardly a shadow to be found. There would at most be a large indistinct fuzzy spot on the wall behind you, where you are blocking the direct light from the window. All the light being reflected from the other white surfaces in the room also serve to soften your shadow by effectively enlarging the area of the apparent light source (the window is the primary source, and the walls reflective sources). It's an almost ethereal atmosphere, or... is that the effect of the paint?
Color temperature, is surely the least intuitive of all light's qualities. Color temperature is a measure devised by William Thomson, 1st Baron Kelvin, which equates the ratios of colors in white light to a physical constant, the behaviour of a theoretical black body at various temperatures. Color temperature is reffered to in degrees Kelvin, another measure devised by the baron. The details of black bodies is not whithin our scope here to discuss. To sumarize this complex scientific description, it is enough to say that color temperatures range from red tones equal to 1800Kelvin, to the tones of bright northern-sky blue at 12000Kelvin. Every light source, man made and natural, has a particular mixture of tones which in turn dictate it's analogous color temperature. The effects of these varying mixtures of tone is best demonstrated by the following example. If you were to hold a plain white card under different light sourcess, the white surface would get reder, whiter, or bluer, depending on the color temperature of the light source it's under. Reds are in the 1000's Kelvin, some examples are candle light, and incandescent lights. Reds turn to yellows on the way to white light. Yellows are in the upper 3000's Kelvin, studio lights render white surfaces yellow. Daylight is 5800 Kelvin, under open sun on a cloudless day the white card will be true white. As we increase the color temperature from daylight towards its upper theoretical limit at 16000 Kelvin, whites become more and more blue. What makes color temperature so elusive to the naked eye is that our brains adjust our awareness to maintain the impression that the surface is indeed white. In other words, even while our eyes register acurately the colors as portraighed by different lights, our brains then readjust the interpretation of the incoming optical nerve signals so that we continue to see white as white. Throughout the changes in color, our brains correct for the shifting color temperatures. Daylight is considered normal color temperature, the color temperature in which all objects are measured for their true color. The camera however, does not automatically adjust for changing color temperatures, which is why there is tungsten color film, and daylight color film. Each of those have been designed to compensate for a particular light source, and render colors true on film, just as our brains do for us automatically. Needless to say, if the photographer misuses the film he has, generally by using light sources the film is not equipped to adjust for, or by mixing in various light sources, the resulting imagery will have a distinctive, unnatural color cast over everything. For example, to daylight balanced film, fluorescents render things rather green, tungsten gives everything a faint amber cast, high pressure sodium lights like streetlights are positively orange, and stadium lighting, along with electronic flash, are rather bluish. All of these color temperatures need to be consciously addressed by the photographer working with color film, and either corrected or intentionally exploited for their particular colorcast. There are few examples of color temperature used uncorrected intentionally. Generally the effects thereof are unpleasant enough that hardly anyone outside of the horror show business is interested in exploiting their unsettling qualities. Green is just not a nice color for skin.
The preceding are the five facets of light. Each has its part to play in defining the final image captured in camera. If photography is the art of writing with light, understanding what the elements of Light are, and how each fits into the intentional act of designing an image, is a foundational step towards penning your masterpiece.
My best wishes-
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