The Shoot That Changed How I Think About Color

A few years into shooting editorial work, I booked a beauty campaign that called for a clean, skin-forward look with a subtle cool shadow on the background. I had two Profoto B1s, a solid white seamless, and what I thought was a decent grip kit. What I did not have was a proper understanding of how a gel on one light interacts with the ambient color temperature of every other light in the room.

I put a pale blue gel on my background light, shot the whole afternoon, and handed off the files feeling good. The retoucher called the next morning. The “subtle cool shadow” had turned the model’s neck a kind of desaturated gray that looked less editorial and more like she was standing in a hospital corridor. The gel was doing exactly what I told it to do. I just did not understand what I was telling it.

That shoot is in my lighting journal with a red star next to it. I have not made that mistake again.

What a Gel Actually Does to Your Light

A gel is a sheet of colored polyester resin that filters specific wavelengths out of a light source. When you put a CTO (color temperature orange) gel on a strobe rated at 5600K, you are shifting that output down toward 3200K, which is tungsten territory. A full CTO drops you roughly 2000K. A half CTO drops you around 1000K.

This matters because your camera’s white balance is set to a fixed point. If that point is 5600K and you shoot a subject lit by a gelled light at 3200K, the skin reads warm on the sensor relative to everything else. That warmth is not random. It is calculable. And because it is calculable, it is controllable.

The problem most photographers run into is treating gels like paint and forgetting they are more like filters with measurable transmission values. Color Rendering Index and light transmission percentage are printed on every Lee or Rosco swatch book. Lee’s Half CTO, catalog number 205, transmits about 53 percent of visible light. That is nearly a full stop of light loss. If you are not adjusting your power output or aperture to compensate, you are not just shifting color, you are also underexposing that light relative to your key.

Building a Gel Workflow That Does Not Guesswork

Here is the approach I use on every gelled setup. I call it the anchor-and-adjust method.

First, I identify my key light and set it ungelled. I dial in my exposure, get the histogram where I want it, and label that light’s power setting on a strip of masking tape on the stand. That is my anchor. Every other light in the setup gets adjusted relative to it.

Second, I gel my fill or background light and immediately compensate for the transmission loss. If I am using Lee 101 (yellow) which transmits around 79 percent, I bump that light up roughly a third of a stop. If I am using Lee 085 (deeper orange, about 42 percent transmission), I am adding close to a full stop of power to hold my ratio.

Third, I shoot a test frame, pull it into Capture One, and use the Color Balance tool, not the white balance slider, to check whether the gelled light is reading the way I intended on skin. The white balance slider lies to you. Color Balance shows you channel-specific shifts and lets you see if a gel is doing something unexpected in the shadows versus the highlights.

For gel selection, I keep two starter kits in my studio: the Rosco 50-piece sample kit (around $25) and the Lee Filters 100-piece swatchbook (around $30). Both are cheap enough to be consumables. I cut swatches to fit my speedlights and tape full sheets to my Profoto heads with Gaffer tape, never masking tape directly on a hot modifier.

When Complementary Gels Separate Your Subject From the Background

One of the most practical uses of gels in commercial work is the complementary split: warm key, cool background, or vice versa. This is not a stylistic trend. It is a depth tool.

When I light a subject with a half CTO on the key and put a quarter CTB (color temperature blue, Lee 202) on the background light, I am creating a temperature contrast that the eye reads as spatial separation. The subject feels closer. The background recedes. You can achieve a similar result in post, but doing it in camera means the color information is baked into the raw file with actual photon data behind it, not a Hue-Saturation layer.

The ratio I use most often for this split is key at 1:1 with the fill, background at 1.5 stops under key. That gives me a gelled background that reads as colored but not theatrical.

One caution: if your studio has any ambient light coming in, a window, an overhead fluorescent, anything, it will fight your gels. I shoot with blackout curtains and turn off every overhead in the room before I set a single light. Ambient is the enemy of a controlled color setup.

Gels That Belong in Every Studio Kit

Beyond the warming and cooling filters, three gels earn their place in my standing kit.

Lee 139 (primary green, about 58 percent transmission) is essential for matching fluorescent ambient sources when you cannot kill them. One full Lee 139 on a strobe at 5600K brings it close enough to match a standard cool-white tube that you can balance in camera.

Rosco E-Colour 10 (medium yellow, around 72 percent transmission) is my go-to for adding dimension to skin without the overt warmth of a CTO. It does something flattering to brown and olive skin tones that I have never found a clean post-processing equivalent for.

Lee 183 (moonlight, about 61 percent transmission) is a pale blue with almost no saturation. It reads as a shadow tone rather than a color effect, which makes it useful for background texture without telegraphing that you used a gel at all.

The most important thing I can tell you about gels is this: know your transmission values before you fire a single frame, because the power adjustment is not optional, it is part of the exposure calculation.