SLC-2L-04: Use a Tight Grid to Create Color

Normally, you might think of a grid spot for what it creates: a tight zone of light. But it also can be helpful to think of it in terms of the inverse: a grid also prohibits light from reaching everywhere else.

And the "everywhere else" part—that relative blackness you can create with a gridded key—is what can help you to amp the color palette in even a small room with light-toned walls.

One Small Room, Three Zones of Light

So I'm shooting some social media photos for a physical therapy practice. And after about the fifth room I am starting to feel like my bag of tricks is wearing thin. We're working pretty quickly, just toting a camera and two speedlights around the office. And we are working in one light-walled room after another.

Rooms like this are great for throwing a flash up into a corner for a nice wash of light. Maybe back up a little and shoot through a doorway to frame your subject. Then let the ambient window light burn in a little and you have a look that appears totally natural when in fact it is lit:

But working within a small, light-colored room, there is not much space to physically hide your lights. And worse, you are basically working inside of a soft box: that light from the flash bounces around everywhere. It's great for legibility, but it is also very tough to control or restrict the illumination.

For the photo up top, demonstrating vestibular rehabilitation treatments, we were in yet another small, light room. But I thought the eye-tracking monitor was pretty cool and definitely wanted to include that.

Zone One

So right off the bat, I knew I would need to have the room darkened so I could use the ambient exposure to burn in the display monitor.

Fortunately this room had no windows, so that would be easy. We just turned off the overhead lights and shut the door. Now our ambient exposure is based on the monitor glowing in a dark room. We adjust the f/stop and shutter speed (making sure to stay below the monitor's scan rate) to record that information.

Next we'll bring the rest of the room to that value, using flash. Meaning, we will adjust the power from our two flashes relative to that predetermined exposure level.

Zone Two

Here's a diagram of the room with the lights included. Remember, before adding lights we now have a black room with a monitor image basically floating in that darkness. Next we'll add some fill light. We'll bathe the room with bounce light, but underexposed, for general legibility within our environment. But since we are building on black, we can also choose to add some color.

Our first speedlight is bare, gets a full CTB gel, and will be positioned on a stand in the camera right corner. It will bounce off of the (thankfully) white ceiling. The flash is close to the ceiling, so the effective light source will still be pretty small. That light is going to be set to underexpose the room by 1.5-2 stops, which will further saturate the blue environment we are creating.

Why blue? It is an easy go-to for a bit of a tech-y feel. And it is a nice complement to the warming gel I am going to use on my key light.

Zone Three

Finally, we get to our key light. I am going to fit that with a 1/2 CTO gel, and a tight grid spot.

The 1/2 CTO gridded key will be pushing into a full CTB fill environment. So those lights will mix. And to some degree, the CTB will mute the warmth of the 1/2 CTO. But not much, because the CTB fill light is underexposed. So in the center of the grid beam, the warmth of the key light will overpower the CTB fill. And that's good, because it'll make the therapist and her patient pop in the blue environment.

And why the tight grid? To protect my blue room from any leakage and contamination from the warm key light. I even gaffed it a bit to make sure no light spilled out of the sides.

The gridded key is critical to being able to build a color base with your fill. With a soft box, or umbrella, or bounce—or even a bare strobe—on the key light, this would not work at all. Because it is the area that is not lit by the gridded key that allows the blue fill light to exist uncontaminated.

Contamination is always going to be your enemy when working with colored light sources. And a grid is always going to be your best tool to conterract that.

FROM: Strobist Lighting Cookbook, Two Lights


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