Color Temperature and Correcting Mixed Lighting with Gels

Today I want to try to give a simple explanation of color temperature and how to correct for mixed lighting situations with gels. First off working with Color Temperature is no different than working any other color. For a very quick and simple understanding of color theory look here. Now, when working with light, we don’t have to deal with full spectrum (all of the colors), we only work with a specific range of color. This range of color is from a dark orange to a dark blue and is measured in degrees Kelvin. For a visual reference and a better understanding, I created a simple chart above.

In order to help you understand, I want to give you a real world example of how you might use this information. Lets say you are out and about in the late afternoon when the sun is setting. As the sun falls, it’s going to be casting a golden color of light. This light is wonderful to shoot in, however you might find that there are some deep shadows that accompany this setting sun. A good idea might be to use some fill flash to control the contrast. Here is where your problem will arise. Your speedlight is not that golden color of light, it’s a white/bluish color of light (5600 mid day sun). When you try to mix the flash with the sun, the result will be very poor. The simple fix is to add a gel to the flash. In doing so, we will change the color of the emitted light from the speedlight from whitish-blue to a golden orange. Simply put we make the light sources match.

Below are three images. The first is the base exposure to insure a proper background. The second is with a flash used to open up the shadows and reduce contrast, note the color temperature mismatch. The third image is with the color gel in place to match the sun. (note, these images are for illustrative purpose only)

This same method works when dealing with any sort of light mismatch. All you have to do is make the strobe color match the dominant ambient source of the environment you are shooting. Example would be if you are in a Gym and the lights are orange in color, put an orange gel on the flash. If you are under those old fluorescent lights in an office building, the ones that cast a nasty green color, just add a green gel to the flash. Always remember, it’s just about impossible to correct a mixed lighting situation in post. It’s your task to insure your flash’s color matches the color of the ambient light source. I’ll say it again, if you insure your light source’s color matches then life is easy in post.

One last tip, set a custom white balance after you have gelled your flash and all of the light sources match in color. By doing so, you can insure proper skin tones and frame to frame consistent results. For more information and a tip to turn day into night, spend a few minutes, three in fact, watching the video below. I hope you all have a great day. Sincerely, Thomas Shue