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Grecco's Laws of Light
Photo by Paula Lerner
When I teach lighting, I often simplify the concept by breaking it down into three main points: the color, or the “flavor” of the light; the contrast, or how it looks from one area of the subject to another; and the softness, or intensity of, the light. This is a very basic and simplistic breakdown, and there are many other lighting factors you need to master to create the portrait you want, but I'd like to start here with the basics—the three components that comprise Grecco's Laws of Light.
Grecco's First Law: The Color of Light
Light sources come in many different colors, or as I sometimes call them, “flavors.” Though you can create a huge array of light flavors using colored gels and filters over the light source, the light source itself possesses an inherent color and each light source's color is different than the next. Some of these light source colors are very easy to identify, like fire, for example, which can be orange to red depending on the temperature of the flares. Household light bulbs also tend to be inherently orange. Fluorescents have a green quality and streetlights are usually yellowish.
The color of the light is an independent consideration from the other components of the image—contrast, softness, and quality. You can alter the color of the light to just about any color you want, but note that radical light-color changes will cause you to lose a great deal of exposure. A filter or gel used to bring out desired colors also filters out certain colors, since filters don't make light, they block light. If there is not a lot of the color you want inherent in your light source, the filter or gel will suppress the colors that are inherently there, leaving you with very little light after the unwanted colors are filtered out. This is especially true when trying to make hot colors (orange, yellow, or red) into cool light (white or blue) with blue (cooling) gels. On the other hand, lights that are inherently white in color can be easily altered with gels to produce a range of colors because white light contains all the colors in the spectrum.
Professional lights are standardized to give you two basic colors: tungsten (which come from tungsten-based hotlights, a continuous light source), and daylight (which is produced by HMI, another type of continuous light). And, there are strobes, or flash units (which are not continuous). There is also a light used heavily in the movie industry called a Keno Flo, basically a fluorescent light source that does not flicker and can produce either tungsten light or daylight. The bulbs come in all shapes and sizes and because they are continuous, can be placed almost anywhere. The color of light is measured in a scientific standard called degrees Kelvin, which indicates the hue of a specific type of light source. The Kelvin scale places white light at 5500o. The color that we associate with this is called daylight balance, which we visually experience as a result of the blue sky combined with the yellowish sun. Tungsten light is placed at 3200o, HMI/daylight at about 5700o Kelvin, and strobe flash ranges from 5000o to 6500o Kelvin, depending on the manufacturer. You should test your electronic flash with a color meter, or find out from the manufacturer what the color temperature of its heads are so you know whether they are warmer than daylight or colder. The lower the Kelvin number, the warmer the light, and the higher the number, the bluer, or cooler, the light.
Grecco's Second Law: Contrast
Contrast, the amount of light and darkness in an image, can be controlled with lighting and exposure—contrast is increased as the light gets closer to the subject. According to the inverse-square law of light, every time you half the distance between the light and the subject, the power of the light increases four times. A light five feet from the subject at f/8 becomes f/4 at ten feet. A light one- and-a-half feet away from the face of a six-foot-tall person at f/8 becomes f/4 at three feet. A light that is one foot away from the subject's face will completely illuminate the face, but leave the rest of the body softer and darker. Moving the same will spread much more evenly from head to toe (a change in contrast.)
This is a very simplified view of contrast. Once you add multiple lights at different settings in different parts of the image, things get a little more complex. But by understanding the workings of each light, you can start to have better control over your images. By moving the light in and out, you use it to more evenly light your background and subject, or, create drama. Just don't set anything on fire by moving your light too close to it. I hate to hear good subjects scream during a shoot; it definitely ruins the mood.
Grecco's Third Law: Softness
Softness in lighting, or soft shadow, is created by having more than one point of light illuminating the subject. If the light sources are very small relative to the subject, as with pinpoint light sources, the rays of light won't wrap around the edges of what's lit (for example, a nose) and the shadows created are very sharp. If the light sources are very large relative to the subject, the light will wrap around what's lit (the nose) from many different points and create softer shadows. Each individual beam, or ray of light, creates a defined shadow, but many rays of light will each illuminate the shadows of the other rays. This will reduce the intensity of the shadow of any individual ray. So, the more rays that strike the subject from different angles, the more diffuse the shadows become.
As light sources get closer to the subject, both the contrast and the softness in the image increase. As one light gets stronger and bolder, the contrast, or opposite light, gets softer. This happens because, as the light sources get closer to the subject, more of the surface area of the subject is lit, and the light wraps around the subject more, converging to create contrast and softness. To think about it another way, the sun is the largest softbox light source in our universe (about 865,000 miles in diameter) but because it's so far away (93,000,000 miles), it's a pinpoint light source by the time it hits Earth, and as such, makes very hard or sharp shadows.
Quality of Light & the Shape of Light
There are infinite degrees in quality between harsh light and soft light. Having the ability to control those degrees for your creative use is essential. Light quality is affected by the things used to modify or alter it. For example, you might use two different same-sized reflectors or beauty dishes set at the same distance away from the subject, but one is shiny silver and the other is white. The shadow each produces would be the same, but the harshness of the light and shadow produced by each would be different—the shiny silver would produce a higher-contrast shadow and the white reflector would produce a softer shadow. This is because the white surface scatters light on other objects, which may act as secondary reflectors (ceilings, walls, etc.). This difference in the harshness of the light and shadow is what I describe as the quality of light. I often use a minimal piece of diffusion on a harsh light source to take just a slight edge off of the roughness without losing all of it, as you would with a softbox.
The shape of light is controlled by how you modify it at the source (by putting a softbox over it, for example) or anywhere in between the source and the subject. Inherently, any soft light source will spread the light everywhere unless spotted or concentrated by some sort of grid. I like to use Lighttools egg crates made for Chimera softboxes, but there are metal grid spots you can put over bare light sources that also spot down the light. The quality and “softness” of the latter would be much harder and sharper because the head is small and has a shiny metal reflector behind it.
[Michael Grecco is a featured photographer of Canon's 'Explorers of Light,' a select group of 60 top American photographers. Visit Canon's 'Explorers of Light' Gallery: www.photoworkshop.com/canon/explorers.]
© Michael Grecco
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