Lighting 103: At Least Use a Warming Gel on Your Key Light

Abstract: Warming your flash will greatly improve skin tones. Which warming gel you use depends on your subject, the lighting environment, your camera's color palette and personal preference.

I still remember the day I was introduced to warming gels. It was nearly 30 years ago. I was assisting photographer Chris Usher in 1988 on a shoot in Washington for Businessweek. As he was setting up his light he asked me to hand him his gels, absentmindedly muttering, "Always gotta warm the key light..."

And I'm thinking, "Wait, what?"

For Chris, warming his key light was already a given. But for me it was a brand new thing, and an "aha" moment. Yet another confirmation that we existed in different universes. But things were starting to make sense now: why his photos looked different than mine; why his light seemed to have more character and realism.

The gel he was using that day was a Rosco 08, one of the more commonly used warming gels, and included in the Strobist Rosco flash pack. So being a good student I proceeded to use an R08 on every portrait I made for the next ten years.

While the Rosco 08 definitely offset the cold, clammy look of bare electronic flash, it was a blunt solution to a complex situation. So let's back up a bit, and start you off with a more sophisticated approach right from the start.

Let's Experiment

Here's a quick lighting test—with typical caucasian skin—from a two-day lighting bootcamp I taught last month in Dubai. This is not a finished photo; it's a quickly grabbed frame in a lighting class. We're just being mannequins here.

Lit by a single umbrella (and the background lit by a separate flash) his skin looks warm and healthy enough. Not bad, actually.

Except that light is already being shot through a Rosco 08, a classic warming gel. Without the gel, his skin would be reacting to the cool blue of the typical electronic flash. Without the gel, he looks like this:

He looks more "lit," because the light has that cool, pasty signature of bare electronic flash. It's less natural. So for this skin tone, an R08 is a pretty good solution.

Now let's take that solution and apply it to someone else.

Here is another student in the class, also lit by the same ungelled strobe setup. Being a native Middle Easterner, she also has more pigment in her skin. More, in fact, than this photo is showing. That's because the slight blue tint from bare flash is neutralizing it.

So let's warm her up with our classic Rosco 08:

Whoa, okay... that's a bit too much isn't it?

The combination of her natural skin color and the R08 is additive, and a bit over the top. Not that there might not be a time and place for this. It looks like the last rays of golden light. But absent that environment, a bit over the top.

But if you are firing a flash through a diffuser (like a shoot-through umbrella) as one often is with a portrait, there is an easy fix. If a gel is too strong, you can "half-stripe" it across your flash vertically, cutting the overall intensity. Now you've just made a lesser-strength warming gel.

Now let's look at the striped, half-strength gel on her:

Much better. And it actually better approximates the real-life appearance of her's skin.

The takeaway here is that, in general, warming is a good way to offset the cool tinge of an electronic flash. But the more natural color people have in their skin, the less warmth you may need to add. Remember, that bare flash will rob them of some skin tone. So it is a good idea to give it back. Whether you want to bump it a little beyond neutral is up to you.

Another Reason to Warm Your Key

When we light, we are creating an artificial environment of light for our subject. Usually, that light is coming from a lower, more pleasing angle than directly overhead.

Yet, direct overhead lighting, also known as 5600K daylight white balance, is what our flash is balanced for. Overhead sunlight is cooler than lower angled sunlight, beause overhead light is being filtered by less atmosphere. And electronic flash feels even a bit cooler than overhead daylight.

NOTE: There is actually a "flash" white balance setting on most cameras. But in the next lesson we'll make an argument for why you should never use it.

As we lower our lighting angle to create more pleasing light for the subject, it is psychologically appropriate to also warm it up. This is what happens in nature. So this is what our brain expects. To not do that is to create light that feels artifically cool and unpleasing relative to what our brain expects.

The photo of Ben at the top of the page, shot for LumiQuest, is a good example (more here). That key light is closer to the horizontal angle than it is to the vertical angle. It needed to be warmed, and it was. I used a Rosco 1/4 CTO gel, which actually has a bit more red in it than does a Rosco 08. Without the gel, light from this angle would have felt cold and clammy.

Your Camera Matters

Each camera model has a different color palette—even when all of the controls are set at neutral. Beyind that, even two examples of the same camera model can look different at the same settings.

When switching form my Nikons to Fuji a few years ago, I also had to change my assumptions for what gels would look best in what environments. And that is before you even get into all of the internal color palette control a Fuji gives you that a DSLR typically does not.

The photo above, of the CEO of a company that makes laser-based ground-to-air data transmission systems, was shot with a Nikon D3. (More on that shoot, here.) A 1/4 CTO on the key light did a pretty good job of giving her good skin tone and integrating her with that red environment.

But if I shot that again today and used Fuji, that whole color palette—and probably my choice of warming gel—would be different. And while we're at it, I'd probably be a lot more aggressive with a red, low-angled fill light. Because I am less scared of that than I used to be.

You need to experiment with your exact camera and your lighting—even if that means doing so on the fly while on a shoot. But of course, it is always better (and more confidence-inspiring) to have tested this stuff out before the fact.

You don't have to overly warm your subject, either. Sometime, just replacing the warmth the photography process takes away can go a long way. Author Manil Suri already has a fair amount of pigment in his skin. But he was shot with a Nikon D3 and a Holga plastic lens, lit by electronic flash mixed with light from an overcast day. And each of those factors will rob color to some extent, compared to full sunlight, Fuji and good glass.

So a 1/8 CTO—not a strong warming gel by any means—essentially replaced that lost color. (The squishiness in the portrait, BTW, is from the plastic lens. More here.)

This photo, from a series of informal actor portraits I did for a local theatre, is a good example of using a warming gel to tie a subject into existing ambient lighting. We used a 1/2 CTO on the key light, and it blended well with existing 2700k (tungsten) environment on the stage.

(Again, shot on a Nikon D3, which would not convey nearly the vibrance as would a Fuji today.)

But here you can especially see the difference between the gelled light and the rim lights which by comparison look almost blue. Those are ungelled, bare speedlights.

I also like to use a warmed key light to call attention to someone's face in an otherwise-neutrally lit environment.

The two-light portrait above is completely lit by flash; there is no ambient contribution. The fill light is courtesy a no-gel umbrella, low in front of Riaz, and powered at about two stops down from the main light exposure. It fills in the blanks in ths shadows left by the key light.

The key light has a Rosco 08 warming gel and is fired through a grid. Both the warm color and the narrow beam of the key light draw attention to Riaz' face. And the added warmth (not too much, as he is already pretty warm) also unifies him with the environment a bit.

Now You Try It

Those of you working with the gels in the Strobist kit (see L103 Prereqs and Supplies) already have several choices for experimenting with warming gels: Rosco 08, vertical half-stripe R08, 1/2 CTO, 1/4 CTO and a vertical half-striped 1/4 CTO (roughly a 1/8 CTO). Those of you with the Beauty pack have a whole world of additional options for skin—both separately and stacked together.

The only way to see which works best with your particular gear (and preference) is to test. So I'll leave you to that. Grab a willing victim and experiment with different gels on your flash while photographing them. See what you like. See what goes too far for your tastes.

Fair warning: as you get further into this, your acceptance of light that is further and further from white will start to expand. It's just like your taste palette probably expanded as you grew from a kid into adulthood.

And to give you some higher-end exposure into the world of warmed key lights, a reading assignment:


Flip through the last half of the Heisler 50 Portraits book, after it makes the shift from black and white to color. Notice anything? Almost every subject gets a warmed key light of some kind. The use of the gels adds realism and warmth—both color temperature and psychological warmth. Those warm lights also ground the subjects into their environments while calling attention to their faces.

Yes, a couple of the photos are key lit with weirdly colored lights: Alonzo Mourning and Robert Ballard, for instance. But another one of the photos should jump out at you, within the context of all of the others.

Take a look at the full-page photo on page 124. Where and when does it look and feel like it was shot? Where was it actually shot?

That photo was an eye-opener for me. As someone who had grown to think of warming a key light "for effect," Heisler was so far past this point that he now sometimes chooses not to warm the key light—for effect.

And in the context of so many of his other photos, grounded in a strong observational knowledge of the color and psychology of light, the absence of that warmth now becomes surprisingly strong.

So, not gelling. For effect. Welcome to the upside down.

NEXT: When Not to Gel Your Flash


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