USING COLOR GELS TO CORRECT OUTDOOR LIGHTING
Color gels can be used for a variety of purposes, many use them to add a pop of color or creative artistic flare to their images. However, they can be used when shooting outdoors to correct the natural lighting and create better conditions for a shoot.
The key here is to understand why one would gel their lights in the first place. You do that to balance or unbalance light colors relatively to the other lights.
To make it simple, just remember this list from more orange to more blue.
- candle light = very orange = 2800K
- tungsten light = orange = 3200K
- fluorescent light = about yellow/orange 4000K
- sunny/ daylight (and flash light) the DEFAULT neutral = white = 5500K
- cloudy light = blueish = 6500 K
- shadow light = very blue = 7500 K or higher
Then what ever setting you set your white balance to changes your lighting to appear neutral, as though its in white light. When outside in sunlight people typically shoot in 5500K.
There are two gels we will talk about today. The first gel is color temperature blue and the second is color temperature orange. Color temperature blue, shortened to CTB, is primarily used to cool down warm incandescent lights so they appear closer to white light. Let's say you're shooting at sunset and it starts to get dark because the sun is going down. Typically you would be shooting with a white balance of around 5000K-5500K outside when the sun is out. You'd also be using a strobe light and the sun would serve as your secondary light source, providing you with a nice white light. Now that the sun is going down, you'll need to raise your white balance to 7000K-10,000K to prevent your background from looking too dark. However, this will result in your subjects looking orange. To counteract that effect you're going to have to cool down your strobe light using your CBT gel, this can be done by securing the gel strip to your light with gaff tape. The end result will be a bright background and a subject that looks as though they are in white light. A good way to think of it is adding cooling gels to your strobe light and then adjusting your white balance to make your gelled light look white.
Color temperature orange gel, shortened to CTO, works in exactly the same way. The only difference is that you would use it when your background is too orange, like when the backdrop of the subject you're shooting is a sunset with a lot of open sky that you want to make appear blue. To prevent your image from looking too orange adjust your white balance to 2500K-3300K and then secure the CTO gel to your strobe light. This will balance out the light and give you a picture where your subject looks like they're in white light with a nice blue sky behind them. Think of it as essentially the opposite of the process of using CTB gels. Keep in mind, you can use different gel strengths to make these effects more or less subtle and you can also shoot at different times of day which will also have a drastic effect on the color in your background.