Thinking About Light

I use to start my color classes asking students, “What do you need to have color?”. The answers were varied and usually wrong. In order to create any image you need thee things; light, an observer and an object. One of the problems that novice photographers experience is they do not understand the language and terminology of Photography. What does it mean to “bounce” the light? What is a key light? What is a strobe light? It is hard for novice photographers to get help from more experienced photographers if they don’t speak a common language. I told a new photographer once that their picture would have been better if they used a hair light. They of course asked, what is a hair light? In this article we will explain some photography terms as they relate to light. It is not meant to be a complete glossary but rather to cover the key terminologies.

The Electro Magnetic Spectrum

First, let’s discuss the nature of light. VISIBLE LIGHT is part of the ELECTROMAGNETIC SPECTRUM. Light, as we can see it, is a very small part of the spectrum from about 400nm to 700nm. Other parts of this spectrum are X-rays, gamma waves, radio waves, etc. While we cannot see X-Rays or Infrared rays, cameras can be used to photograph these waves. Visible light can be NATURAL LIGHT from the sun or ARTIFICIAL LIGHT from INCANDESCENT or FLUORESCENT light sources. Color properties of light are expressed in KELVIN notation. Natural light is about 5000K to 6500K depending on the angle of the sun and location on the earth. On a shady day, the sun may only be 4800K. Modern Digital SLR cameras have automatic WHITE BALANCE controls that automatically adjust for color temperature. Incandescent light has a color temperature of between 2800K and 3200K providing a yellowish green light. Regular fluorescent lights have a color temperature of about 2900K, however you can buy color corrected fluorescent lights that have a color temperature equal to daylight. These are used in print evaluation rooms and even in some studios.

Visible Light

A color GAMUT is a DEVICE DEPENDENT color space that provides a visual representation of the color characteristics of that particular device. The “shoe sole” large area represents VISIBLE LIGHT and the plotted area within shows the COLOR GAMUT of the device which is in this case an SRGB COLOR MODEL. Of course you can’t have COLOR without having an OBSERVER. If a tree falls in an unpopulated area does it make a sound? No, it makes a WAVE but you need a listener to have sound and you need an OBSERVER to have color. Since we all see color differently, the CIE created a STANDARD OBSERVER so that we have a common language when we discuss color. This is built in to all color models, color spaces, spectrophotometers and colorimeters.

CIE Color Gamut

Now that we know a little about light, lets talk about LIGHTING. This is a standard studio portrait lighting set up. The KEY light is also sometimes called the MAIN light and it will create the most important shadows in the picture. The FILL light is used to fill the shadow, it may be the same strength as the KEY light and less strong to provide a deeper main shadow. The BACKLIGHT is sometime called the HIGH LIGHT or HAIR LIGHT and in a portrait setting will be used to provide a highlight in the lighting plan. The BACKGROUND light is use to light the background to give the image a more three-dimensional look.

Four Point Studio Lighting

There is a huge variety in Studio lighting from the LIGHT BANKS used by movie studios and rock concerts to simpler setups for professional photography. Photographers CONTINUOUS LIGHTING options come in cooler fluorescent light banks color corrected to 6000K. There are also less expensive and hotter INCANDESCENT lighting that has to be color corrected with light filters or by adjusting the film or camera white point.

Studio Incandescent Light

The more popular type of studio lighting is FLASH or STROBE lights that are only on during the exposure, which is usually 1/80th of a second. This creates a unique photographic problem. How can the photographer set up his studio lighting when it is dark? How can you evaluate the shadows and highlight created on your subject. Many professional strobe lights have a built in MODELING light, which is a low wattage incandescent light that you can aim on the subject to set your lighting angles. The modeling light may stay on during exposure. This will not create a color balance problem since the intensity is very low compared to the STROBE lights. You can also use regular incandescent studio light in combination with strobe lighting if your lights do not have modeling lights.

Studio Strobe Light

In studio light setups, strobe lights may have a main light and SLAVE units that are SYNCHED to go off when the main light is triggered. Photographers use UMBRELLAS and BOUNCE the light into the umbrella with the reflection for the umbrella used to light the subject. This creates a softer light. You may also use DIFFUSERS that go directly over the light to soften the light further.

Studio Umbrella Bounce Light

Experiment with lighting and capturing objects to develop your lighting skills. Have your friends’ model for you so you can practice your lighting skills. To see images from my commercial portfolio, click here.