The Wheel of Color is a Crafty Mistress
Posted by Keith · March 18th, 2008Your eyes are some funky organs. They perform a whole throng of
calculations and functions every second, almost all going unnoticed by their owner and occurring, forgive me, in the blink of an eye. It’s because of this artful sneakiness that we have to deal with color temperature issues when shooting on video or film.
Typically, indoor lighting fixtures will emit more of an orange light than that of outdoor conditions, which is bluish. The eye is quick to adjust so that color appears normal to your vision, without the various tints of orange or blue. Video cameras do not work in this way, unless we tell them to. They pick up the variations in color with no normalization, so that when we view our recordings in playback we may see a tint of color that wasn’t noticeable to us while shooting.
This is why Color Balancing is so important. You must give the camera a reference point so that it can determine the correct look of all other colors. In videography, we use white as that reference, which is why you may have heard the term “White Balancing.” To white balance, you take an object that is white, like a piece of paper, and place it beneath the lighting conditions. You then fill the camera’s frame with the object, so that it sees nothing but white and then indicate to the camera that all other colors must be fall in line with this one.
I’ll explain: light is a heat source. It’s is created by electrically charging thin pieces of metal filament and inert gases. This process, in turn, gives off thermal radiation. The intensity of this emission registers at different locales on the visible spectrum, depending on the properties of the wavelength.
You’ve probably observed that the color of the fire flickering on a candle is a pleasantly warm orange, while a gas stove’s flame is usually a light blue. Or you may have noticed the gradient change, from blue to red to orange, in the flame of a match. This is because the hotter, or more intense, flame burns at a different color than the cooler. It emits light that is more excited than the latter, giving off a higher frequency wavelength. This relation between color and heat radiation holds true for any and all light.
To emphasize this point, when scientists measure light intensity, they use the Kelvin scale, a temperature measurement. Candle light measures around 1850K on the scale, while a standard light bulb may fall anywhere from 2800K to 3300K. Sun light however is much warmer and can be a high as 6500K.
These calculations are important to the photographer because of how our eyes deal with these changes. The eye is an organ of normalcy; it works diligently to accommodate differing situations. Notice when you first walk outside that the sunlight is generally very intense, almost painful. But the eye registers the change and adapts to the new conditions by closing the iris, restricting the amount of light allowed to pass to the nerve receptors. So does it adjust itself when color conditions change.
In the digital world, colors are assigned a number. So if say that white is 100, and black is 0, then when you designate one of these, all other colors must fall in line accordingly. So, when you tell the camera that a certain color is to be called white and given a value of 100, you are in essence removing all color tinting that may occur due to different temperatures, and normalizing the picture, just as your eye does automatically.
In amateur videography, you will generally only concern yourself with two different settings: indoor and outdoor (or orange and blue light). When working professionally, there are many differing grades of light color, some fixtures even emit a greenish hue. But talking of such will bring us into a realm of convoluted information and utter sadness, so we will end the lesson here.
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Tags: color, white balancing | Posted in Video Production and Publishing |
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