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In over 30 years of making optical filters, Ira Tiffen created the Pro-Mist, Soft/FX, Ultra Contrast, GlimmerGlass, and others, netting him both a Technical Achievement Award from the Academy of Motion Picture Arts and Sciences and a Prime-Time Emmy Award. Elected a Fellow of the SMPTE in 2002, he is also an Associate member of the ASC, and the author of the filter section of the �American Cinematographer Manual.�

Look around you. What do you see? Perhaps, not quite what you are thinking. What you really see aren�t the objects you would describe, but more accurately, the light reflecting from them, or that emanating from the light source itself. While you may know this intuitively to be true, you can prove it by eliminating the light. Can�t see anything then, right?

So we routinely experience our world through the medium of reflected or emanated light.

Think more about this, and you�ll realize that this is central to the reason why cinema and television images have the power they do to convey ideas and emotions, transporting the viewer into another space and time and mind. We are used to knowing our surroundings in large part (visual stimuli make up the majority of environmental data input for most of us) by relaying the reflected light through our eyes into our brain, which sorts it all out. We see not so much by contacting the objects around us but by collecting the light coming from them.

The camera is the eye of the viewer. And its power comes from its ability to capture and replay light � light that is most often reflecting from the objects it sees. Using the camera is ultimately like turning a light on in the mind of the viewer.

But what is light? We certainly take it for granted when it comes to making movies. That hungry dinosaur, lumbering after us and frightening the little ones; the euphoric vision of liftoff as the astronauts head for the stars; the poignant intimacy of a couple after they struggled past obstacles to be together; all are, after all, just light emanating from the screen, large or small. And with that light, when artfully crafted, comes the ability to let us experience the shock, the horror, the joy, the humor, and the myriad other emotions we encounter in films.

The relationship between light and our mind goes beyond color and contrast. The patterns formed tell us many things about our environment, even if it is the two-dimensional one onscreen. The relationship between the light coming from the screen and the light we are used to experiencing our environment through is therefore of great importance to the filmmaker. So let�s consider: What is light? And what is important to know about it to help us communicate most effectively?

Technically, light is part of what we call the electromagnetic spectrum. This embodies that wide range of energy around us that we measure by frequency and wavelength. Only a narrow portion of the overall, having wavelengths from about 400 nanometers (1 nm = 1 billionth of a meter) to about 700 nm, the visible spectrum, is visible to us as light. Shorter wavelengths run into the ultraviolet (UV), x-rays, and gamma rays; longer wavelengths into infra-red (IR), microwaves, radio and television and beyond.

We work within the visible spectrum as that is what our eyes are sensitive to. Our recording media are therefore designed to work in that region as well, although there are some extensions into the UV and the IR that will be good to know about.

The array of colors we see are all defined by wavelengths: blue centersaround 450 nm; green around 550 nm; and red around 650 nm.

This leads us to some interesting and useful concepts. White light, that which we see as white, is essentially light having roughly equal distribution of light energy throughout the visible spectrum. Thus, similar amounts of light, centering on the 450, 550, and 650 nm regions, when added together, cover very nicely the full range from 400 to 700nm. This leads us to the concept that adding red light to green light to blue light creates white light. That�s the additive concept of color, and you see this in live theater when lights of various colors overlap onstage and mix to form other colors including white.

Film and digital video function in a similar manner, mixing red, green and blue light in different ways but to the same end: to make white, black (the absence of light), and all the shades and colors between (by changing the relative proportions of the red/green/blue mix).

Let�s move to a practical example. The sun is shining. Its light is generally considered to be white, including light at all wavelengths, effectively of all colors. A red object in the scene appears as red because it has the property of absorbing green and blue and reflecting only red. This is true as long as there is red in the light to start with. Same is so of all the other colors we see � they are generally a product of the quality of the light plus the characteristics of the object it reflects from.

If the light is missing certain parts of the spectrum, such as with metal halide lighting, then objects reflecting light in that missing spectrum will appear colorless, or gray, in comparison. Turn on a white light, and they regain their color again. So, again, it is important to remember that what we see is a function of BOTH the quality of the light PLUS the reflection characteristics of the scene.

With camera filters, we are introducing yet another variable, one that allows us an additional level of image control. Once the light reflects from the various scenic elements, we can fashion it further to our liking with filters.

In managing color, filters work differently from the theatrical lighting example earlier. Rather than adding color, they subtract, by either absorbing or reflecting, certain spectrum bits, thus creating a new bias that enhances other spectrum bits.

So camera (and lighting) filters don�t inherently add light (unless you�re using an ARRI Varicon, but that�s for another time); they remove light and leave us with a better mix in some way. Looking through a red filter will not be adding red light, but will remove, through absorption, blue and green and transmit only red. You can see the similarity in concept between what the red filter is doing and what the red object is doing � both are absorbing blue and green and either transmitting or reflecting red.

We will return to this concept many times in our efforts to make the most effective images. From producing the warm glow of firelight, to the cold blue of arctic ice, what we know about controlling color and its effect on our mind will help us to tell our stories most powerfully.

Before we go, let�s look at some everyday examples of natural filters that our understanding of light and color allows us to more fully appreciate. Ever been asked, why is the sky blue? Or wondered that yourself? Well, the answer is tied to the reason that sunrise and sunset are red. Here�s what�s happening. Light from the sun comes from a distance so far away that, for practical purposes, all the light striking the earth arrives in parallel, traveling at the same angle. However, as the earth turns, the part we are on will alter the direction that the light actually strikes us at as we go from day into night and back again.

When we are in daylight, the sun�s light is striking us most directly, and travels through the smallest thickness of atmosphere. It happens that atmospheric thickness and characteristics are such that it scatters the shorter wavelengths first, starting at the blue end of the spectrum. This scattering of bluish light, reflecting from the water and other materials in the air, creates the familiar blue sky we know and love.

As the world turns, our sunlight arrives at an increasingly oblique angle until the sun sets over the horizon and we enter nighttime. As that happens, the light travels through an ever-greater thickness of atmosphere, along the edge of the earth�s perimeter, until it is so thick that it has absorbed or scattered all the bluish light, on through the yellow and the rest of the spectrum until only orange and red are left. Causing, of course, the blazing colors of sunset.

One more thing. When looking for the gold at the end of the rainbow, remember that rainbows are themselves a form of natural filter � sunlight split into its component colors by the prismatic effect of atmospheric water droplets. By understanding these properties of the light you use to tell your stories, you will also become more adept at helping your viewers find that pot of intellectual gold, as well. Let alone any other forms of gold that may come your way�

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Check out this article in the March 2007 print edition of StudentFilmmakers magazine, page 6.