Lighting 103: When Not to Gel Your Flash

Abstract: Don't bother gelling a scene that is completely lit by a single flash. But if a second light is involved—even ambient light—it's always better to control color at the source.



PIctured above is Midwest Camera President Moishe Appelbaum. He wandered into a lighting class I was teaching at Midwest last fall, so we pulled him aside and shot him. He's lit by a single LP180 speedlight, fired through a white bed sheet.

(Pro tip: A speedlight fired through a bed sheet will rival the light of the most expensive octabanks in the world—in quality if not in quantity. It all comes down to square inches in the light source. And a bed sheet has a crap ton of square inches.)

After our previous lesson, you might think that this photo is an ideal candidate for a warming gel: caucasian skin, warm background, warm-colored clothing. Why not unify this with a little added warmth?

The added warmth is a great idea, but gelling to get it is not necessary. That's because this portrait is entirely lit by a single flash. There is no ambient light component at all. Meaning, all of the light in this frame is coming from the same, single source.

So we can just as easily warm (or cool or green or purple) the photo after the fact in Lightroom or Photoshop. That's because in a single-light photo, applying the color shift to the two-dimensional photo is the same as applying the color shift within a three-dimensional environment.

And because we can color-shift the photo in a variety of ways in Photoshop—with near infinite control—in this instance it makes sense to do so after the fact.


Why Not Just Use Photoshop All of the Time?

Good question. Lighting and Photoshop are different, because lighting is three-dimensional and Photoshop is two-dimensional.

When you are lighting a photo, the scene still exists in three dimensions. Typically, different areas of the scene will be lit with different lights. Even the same object can receive light from multiple directions and sources.

Let's take a look at a scene with just two light sources, a speedlight and a sunset:



This is a good example for two reasons. First, the speedlight has been warmed significantly. It is meant to look like a bare tungsten light bulb, so we used a full CTO gel on it. (More info on this shoot, here.)

Second, the light is right in the middle of the scene. So it is radiating light into the scene omnidirectionally, and three-dimensionally. Both of those light qualities (the location the color) create a color and lighting contrast that separates the subjects from the environment.

Could you do that with a white light and then go in and Photoshop it later?

Technically, yes. But it would be painstaking, pixel-by-pixel work.

And this is just one artificial light. What about a scene that has five lights, all with different color temperatures, interacting on the same objects?

It would be all but impossible. It is far easier, quicker, and more accurate to stick small pieces of colored polyester over your flashes.

Doing it the right way also opens up new possibilities in your photos. We already know we can visually map three-dimensional objects with an off-camera light or multiple light sources. Similarly, we can also map those transition areas on three-dimensional surfaces and textures with light from multiple sources of different colors.

It's those "color mix" areas that not only provide different shape/texture cues, but can also reveal the luminous subhues in skin that make a photograph look more painterly. We'll get to that soon.

For now, the main idea is to convince you that "lasso + curves" in Photoshop is not the same thing as gelling a light source.


What About Using the Flash White Balance Setting?



The "flash" white balance setting on your camera is a global shift towards slightly warmer. And yes, it may make your flash-lit subject look a little better. But the effect is global; it warms everything, not just the subject matter illuminated by your flash.

For instance, in the portrait above, setting the white balance on "flash" would have given baseball player Aidan McGonigal warmer skin—perhaps even similar to the effect of the Rosco 08 gel I used on my flash. But it also would have robbed some of the rich blue from the dusk sky. By using a warming gel, I could get both a nice skin tone and a rich blue sky right out of the camera.

This brings up another good argument for gels vs. Photoshop: these images are what my files look right on the back of the camera. After I get my exposure dialed in, I can show the realtime result to my subjects during the shoot and create a positive feedback loop that makes for better photos going forward.

Which is always better than, "Don't worry, you'll look better in the final version after I Photoshop it."

So my advice is always to pass on the "flash" white balance setting and instead work within the "daylight" white balance setting on your camera. You can adjust your light from there by gelling your flash as needed.

Not only will this give you a consistent starting point, but as we'll see later, daylight white balance will also allow non-white environmental ambient light color to better express itself. Which will make your photos feel more organic and natural.

The lack of warmth in flash photos is a flash problem, not an overall scene problem. Solve it at the source with a gel. If you think about it, the mere inclusion of a "flash" white balance on our cameras is a tacit admission that our flashes tend to be slightly blue and pasty and often need to be warmed up.




NEXT: Using Gels to Color-Correct an Ambient Environment