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Why Does Gel Burn?!


All the posts that I published so far are some what serious, mostly because of the topics. To change the mood and also show the other side of me, I have decided to start a series of “whys in lighting.” These are things we took for granted but don’t know the fascinating reasons behind it.

Let’s kick off with this, why does gel/color filter burn?

To explain this, we have to start with the basic lighting color theory. There are three primary colors in the light world, red, blue and green, which is different from primary colors in paint. The result of mixing them all together is way different too, instead of getting some really dark, close to black, color. When mixing all three primary color lights, you get a bright white light.

As we know, there are tons of color filters out there, how do they produce “colors” when you put them in front of a light?

Our color filters, doesn’t matter what kind of materials they are made of, are using a “subtracting method” to produce colors. They filter out the colors we don’t want and only lets the color we want through. Which means, if we put on a piece of primary red in front of a lighting instrument, any other colors of lights pass through the thin piece of gel that are not red would be absorbed and blocked. In the process of doing so, the lights it blocked and absorbed would produce heat and cause the gel to burn. That also explains why dark color gels burn more easily than light color gels. The little piece of gel is actually working very hard sacrificing itself for our gain!

If you ever get your hands on a color filter swatch book both physical and digital, you will see information similar to what you see in the picture here. There is a transmission number shows you how many percentage of the light this gel lets through. Which means the lower it is the more light it blocks and the more easily it burns.

The app I am using also provides information on transmission rates for each color. It is very helpful especially when it comes to programming color mixing moving lights or LEDs. It is not always accurate but it gives you a starting point.

We can also see another set of initials here C, Y, M. They represent the secondary colors in light. Cyan, Magenta, and Yellow. Here is how they come about, Blue + Red = Magenta; Blue + Green = Cyan; Red + Green = Yellow. A lot of the moving lights are fitted with CYM color mixing module instead of using primary colors. Because the secondary colors lets more light through from the beginning, it makes it easier to preserve intensity when you put all three filters in front of the light source to create the color you desire.

Hope this helps! Until next time!!

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