The Basics of Color Gels in Photography

The use of strong, complementary colors is a growing trend in photography. Many modern ad campaigns feature bright, contrasting colors in order to draw your attention to the product or message they are trying to sell. One way to create such vibrant colors in your own images is to use color gels (also known as color filters, filter gels, lighting gels, or simply gels).

Learning to work with gels can help your work stand out among the crowd and deliver eye-catching results. In this article, we’ll look at how to use color gels to add a creative touch to your lighting, opening up a world of possibilities for your photo shoots.

What are color gels?

Color gels are basically semi-transparent thin pieces of plastic (usually polycarbonate, polyester, or another heat-resistant type) that change the color of your light.

There are two types of gels used in photography: creative color effect gels and color correction gels. The former will be used primarily to create various color casts that have nothing to do with the temperature of the light source. For example, if a red gel is placed in front of a light, it will turn it red. A yellow gel will make it yellow and a blue one blue. These are different from temperature and light tint adjustment gels, which are used to balance light sources with the ambient lights around you.

Temperature Correction Gels

Temperature adjustment gels will make a light source “cooler” or “warmer” depending on what is being used. For example, a CTO (orange color temperature) will make a light warmer, while a CTB (blue color temperature) will make it cooler. CTO and CTB gels can be easily confused with orange and blue gels, so it is important to understand that these gels are not the same, and will not give a similar effect at all. I remember once trying to recreate sunlight using a yellow gel, only to find that it didn’t work at all.

A third seldom-used gel is green plus/minus. This will give the light source a green or magenta hue. Essentially, there’s a gel for each end of the “temperature setting” scale: CTO, CTB, less green, more green.

A selection of color gels.

A word of warning: Before going any further, you should know that gels can melt when placed on a hot light source. It’s a good idea to buy high quality heat resistant gels designed for theater lights or avoid using modeling lights unless they are LED lights with a proper cooling.

The basic rule of color gels

Now let’s see how to work with gels. Starting with the most basic rule of every gel: it reduces overall light output. Think of gels as obstacles that cut off some of the light’s power. Some gels like Profoto and Expo Imaging can show how much light each gel cuts. Thus, a blue gel cuts four stops of light, while a yellow only cuts half a stop of light. You may want to intuitively dial in the power up and use gels on the strongest light you have.

Let’s see what light attenuation looks like with a gel:

As you can see, the less light, the more saturated the color. So when setting up a gel, the first thing you want to do is lower the power and then adjust it to achieve the look you’re trying to achieve.

There will be some sweet spot between a saturated dark color cast and a burnt overexposed gel hit. That’s not to say one is right and the other wrong – I deliberately create dark, overexposed looks based on what the image dictates. I like to use very low power light with gels because as you know by now less is more when it comes to working with color gels.

Let’s look at some practical examples where I’ve used gels for effect and I’ll tell you exactly what I did and why.

Using color gels on a fill light

Because gels always appear in shadows and require very little energy to do so, I created a blue room in the studio simply by gelling my fill light. As you know, accent lights are designed to lift shadows and be “invisible” themselves. A great way to fill out a shot is to bounce your flash off the ceiling and light up the whole room.

Although you may think blue is a traditional accent light, it’s actually not. As the most attentive will notice, there is a shadow cast on the bottom. The trick I used was to place a small light source very far away and gel it blue. The shadow helped add definition to the photograph. However, due to a strong exposure difference between gel and key, I was able to get a band of clean white light which then slowly faded into blue.

Using Color Gels for Background Gradients

Who doesn’t love a nice business-looking gradient? For this image, I wanted to make the gradient as smooth as possible while having a noticeable difference between the top and bottom.

To do this, I used a black background and placed a diffuse umbrella with a blue gel at the bottom. The reason I wanted a large light source was because the background wasn’t perfectly smooth and all the creases were showing.

background painting

This is where I feel like Jackson Pollock, what I mean by that is I can just play with different lights in different positions. Having a bunch of Cinefoil, flags, grids and stuff helps me create shapes and patterns with light.

There’s really no clear way to paint your backgrounds with gels. You can either create smooth transitions or have clearly defined lines.

For the image below, I used three lights to illuminate the background: a blue, pink, and yellow light. The pink had a very tight grid so I only got a speck of light, while the blue and yellow had barn doors so there was sort of a horizontal line dividing the colors.

Background and subject painting

How many lights are there in this picture? If you answered three, you are correct. There is a blue light, a warm CTO and a large fill light which is a full CTO. The two spots you see were created using a very tight 5 degree grid. Because the grid was not perfect, the spots have a strange shape. In this case, it makes the image slightly imperfect but also much more interesting.

Use of color gels as lens obstructions

Finally, another way to use gels without putting them on lights is to place them directly on or in front of your lens. This process is meant to bring out interesting blurs and distortions to help create a unique final image. With this method you can capture some reflections off the shiny gel surface, some diffraction, and maybe even end up coloring in some of the shadows.

An interesting approach would be to illuminate the gel you have wrapped next to your lens by placing a light just below the camera. There is no exact science to this, so you just have to try and experiment with what you have to see what happens.

Final Thoughts

Working with color gels is a lot of play and always feeling like a beginner, or at least feeling free. Whenever I work with gels I never think about the theory of what does what, I just put it on a light and see what it creates and then go from there. The wonderful thing about this is that you can be as creative as you want when adding color to your lighting with gels.

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