The power of color

The color can acquire a strong symbolic charge towards the interior and exterior of the painting. When it comes to achieving images that have the ability to convey emotions and tell stories, the function and sense of color cannot be subordinated to the technical demands of verismo or photographic realism.

The filmmaker who wants to appropriate the power of color must understand the subtleties of its handling, and the basic concept he needs to reinforce his skills as a photographer: color temperature.

A practical way to appropriate the concept of color temperature is to acquire the habit of observing carefully and critically all the sources of light that are part of our daily lives.

For example, the dominant color of a candlelight is yellow. The light coming from a cloudy sky is bluish. Each light source has a characteristic color, related to the physical process that originates it.

In order to accurately describe the chromatic variations of light, a scale related to the physical temperature variations of a hypothetical "black body" has been implemented. The idea is that if the reference object is heated to a certain temperature it will emit light of a characteristic color, and the color will vary with changes in the temperature of the object.

Each temperature level then corresponds to a hue in the color of the light and can therefore be described in degrees Kelvin (ºK).

When we say that the light of a candle has a color temperature of 1000ºK, it means that the "black body" should be brought to this temperature (approximately 730 degrees Celsius) to emit a light with the same yellow hue. For the same "black body" to emanate a color as bluish as that of daylight it would be necessary to reach more than 5000ºK.

For example, when turning on a domestic lamp the filament is heated to emit light of 2400ºK. But if a dimmer is used to halve the voltage of the current, a more reddish light will be obtained, with a color temperature of about 1300ºK. And if an excessive voltage is applied, before bursting the filament will deliver slightly bluish light, possibly reaching a temperature of 4200ºK.

Normally we do not appreciate color temperature differences because the brain makes an effort to eliminate the differences that the human eye can perceive.

For example, if we see a sheet of white paper, it is very likely that the perception of color is appropriate regardless of whether it is illuminated by a candle or by daylight. In any case, the brain will "compensate" for the image so that we see it as a sheet of white paper.

However, neither photographic film nor video cameras have the possibility of making equivalent compensation on their own. In the case of film, manufacturers offer various types of balanced photosensitive emulsions for light sources of different color.

Appropriate materials are usually available for tungsten light (3200ºK) and others for daylight (5600ºK). If the appropriate film is used with the correct processing, a photographic image will be obtained that will faithfully reproduce the colors of the original.

In the case of video cameras it is necessary to filter the light that affects the photosensitive elements, in order to "help" the electronic systems to obtain an adequate representation of the colors of the original.

The black and white balance functions are intended to adapt the electronics of the video camera to the light conditions, but by themselves they are insufficient to obtain a correct reproduction of the color. That is why most video cameras include optical filters that allow working with dominant temperatures of 3200ºK (tungsten light) or 5600ºK (daylight).

The basic resource for controlling the color of light in difficult situations is the application of color filters to the camera lens or light sources.

There is an instrument on the aftermarket for photography that allows measuring the color temperature of the incident light: the reading of the thermocolorimeter is given in degrees Kelvin, and through a series of comparative tables it is possible to determine the filtration values that are required to balance the color of the light in a given situation.

It is generally more practical to apply filters to light sources, which allows for greater creative control over the resulting image. In fact, in most cases successful lighting is the one that provides elements of color that, despite leaving the perfect balance, manage to bring a dramatic value to the image. However, it will always be necessary to understand the basic principles of color temperature management before you risk exploring new terrain.