SLC-0L-01: Flash or Continuous, Light is Light

In Lighting 101, 102 and 103, we learned to control our flashes. In the Strobist Lighting Cookbook, we're expanding that approach to learn to move in a fluid way between flash and continuous light.

Understanding flash helps us to solve problems that exist in our ambient light. Understanding ambient light helps us to create lighting with our flashes that much more closely resembles the light found in real life. The two go hand in hand, espcially when we are combining and balancing them in a single photo.

Being an "ambient-only" photographer is very limiting. But being tied to your flashes, to the exclusion of seeing and using great ambient light, is also limiting.

Light is light is light. That said, certain kinds of light give us special advantages that help us to make better pictures. For instance, the (near) instantaneous quality of flash allows us to crank up our shutter speed, open our aperture and make that flash's light contribute a powerful effect to our exposure. It's like magic in a little box.

That quick pulse of light from a flash can also be used as a shutter speed of its own, freezing very fast action—as long as there is not too much ambient light contributing to the exposure.

But other than that, flash and ambient are pretty interchangeable. And ideally, you want to be able to recognize the best lighting solution from either side—or the best combination of the two.
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Whether your light is flash or ambient, you can think of it as having four general qualities. Absent the exceptions listed above, whether it comes from the sun or a candle or a fluorescnt tube really doesn't matter. It's all about the qualities.


1. Color

One of the most noticeable qualities of light is its color. Even subconsciously, we gather lots of information about a scene based solely on the color of the light.

As we talked about in Lighting 103 manipulating the color of our flash lighting is one of the best ways to improve the realism in our light, and to make something look less "lit."

Overhead daylight—or neutral flash— is white. Low-angled sunlight (or a CTO-gelled flash) is warm. Firelight (or a double-CTO'd flash) is super warm. Sunlight well below the horizon (or a CTB'd flash) is blue. Etc.

Natural ambient light—including man-made artificial lighting—is all over the spectrum. And that chromatically complex palette of light adds dimension and realism. Understanding the color component of ambient light, and applying it to your flash lighting, helps you to move seamlessly between the two.


2. Direction

The direction of light reveals the form of the subject. The difference between the camera's point of view, and the light's point of view, is what creates shadow and three-dimensional relief.

These were among the first concepts we learned in Lighting 101. But we can also apply this approach to continuous light as well. Even, as we'll soon see, to continuous light coming from a fixed position, such as sunlight.


3. Softness

If lighting direction reveals form, light softness informs surface and texture. It reveals physical properties of our subject.

As we learned in Lighting 102, soft light can also be used to create an artificial tonal range on a subject, through the controlled use of specular highlights.


4. Beam

The sun is a "bare-bulb" style of light, radiating spherically into space until, 93,000,000 miles later, it hits us.

That is how the light from your small flash starts, too. Every speedlight has a grain-of-rice-sized flash tube that sends light out in all directions, but is quickly gathered and controlled by your flash's reflector.

The zoom controls on your reflector spread or restrict the beam accordingly. Similarly, the bare-tube quality of light from the sun can also be restricted by its environment.

Imagine you are sitting in your bedroom near a west-facing window at sunset. The window would restrict the path of the sunlight, allowing only a beam to pass into your room.

Specifically, it would be a narrow, hard, golden/red beam, coming from close to the horizon. Those four attributes are what define the quality of sunset light streaming through a window. And you already knew that intuitively, before you read this paragraph.

So, flash or continuous, if you wanted to create sunset window light in your frame you would need to replicate those four attributes.

It is how you control those four qualities of the light you use that is important, not whether the light came from the sun or a flash. And whether you use a flash or continuous light is usually a matter of which is easiest, most convenient, or even possilble.


For Example

The photo at the top of the page is of actress Margo Seibert. When I arrived at the farm to photograph her, I had with me all manner of flashes, stands, light softeners, etc.

But the low afternoon sunlight also offered us all kinds of possibilities. So we were opportunistic, moving from spot to spot as the changing light led us to our next look. We were able to work very quickly (no setting up or moving the lights) and get a nice variety of looks in a very short amount of time.

And it was only after the sun set that we brought out our first flash and did some "lit" portraits.

The photo at top looks lit. And it was, but not by flash. It was lit by the warm, hard, low-angled, wide-beamed sun behind her. I took that light and bounced it off of a poster board that had been partially covered with aluminum foil, and that had a hole in it. (I shot through the hole.)

Here is the posterboard seen from the side (but seen after we lost our sunlight):



Could I have done this with flash? Yes.

I would need a very powerful flash, placed far away (to get that tight ratio of direct light to reflected light). I also would have needed either an ND filter or some sort of high-speed-sync solution to be able to shoot wide open for an out-of-focus background.

In short, I could have done it with flash. But that would have been more difficult, slower and much more expensive.

Heck, now that I think about it I could totally make this photo with a poster board, some foil and my iPhone. Light is light.

In that moment, using ambient light was a far better approach. But next time, if that ambient were not available, I could always default to a solution using flash.

Which, in a nutshell, is why you want to be both bilingual (and fluent) in both ambient and flash.


FROM: Strobist Lighting Cookbook, One-Light