When photographers consider their options for lighting a scene, they typically choose between using natural light or flash. While natural light provides a beautiful light source for many scenarios, the simple truth is that flash opens up more opportunities to create incredible photos, no matter the lighting conditions. In fact, it can convincingly simulate a variety of natural light looks as well, including soft window light and golden hour, among others. What’s more, the “flash” option also includes an often overlooked cousin in photography in the form of constant lighting. Each of these outlets for added light has its unique place, or its time to “shine,” and both are worth getting to know. Below, we’ll look at the benefits of using flash vs constant light to illustrate why it’s worth investing in lighting gear and to help you know when to use one over the other.

What Is Flash? What Is Constant Light?

The more we familiarize ourselves with our gear, the better we’ll be at using it to consistently capture shots that match our vision. This holds true for pretty much all gear, but it’s especially important when it comes to lighting gear, which shapes the main ingredient in all photography: light. That said, the first thing we need to do is distinguish between flash and constant light in technical terms.

Flash

flash vs constant lighting rain photography idea
Backlit flash used to capture details of falling rain

Flash lighting, also known as strobe lighting, refers to the use of flash units that emit short bursts of light. The amount of time that these bursts of light last is known as flash duration, which you can learn more about here in our article on the subject. For now, just remember that flash duration simply refers to the short duration of time (e.g., 1/1000 of a second) that the flash emits light when fired.

flash vs constant window light at night
The look of natural window light captured at night using a Profoto B1X and two layers of diffusion cloth. See the technique here.

Flash lighting can be created using a variety of speedlights or strobes that vary in size and power, with options ranging from small 70+ Ws (watt seconds) on-camera speedlights to 2400 Ws studio packs like the Profoto Pro-11!

Mastering the art of flash photography does require a bit of practice, but advancements in wireless flash technology and intuitively designed interfaces have simplified the learning process. We’ll get more into detail about when you should consider using flash below.

Constant or Continuous Light

Unlike flash, constant or continuous lights stay on and provide consistent light until they’re either turned off or the battery dies. Constant light sources include everything from standard flash lights to overhead lights in a room, not to mention the sun! For our purposes here, however, constant lights will refer to continuously running artificial lights that photographers use to light their subjects, whatever they may be.

constant chiaroscuro lighting photography lessons from classic painters

We can use constant lights in much the same manner that we use flash, with similar modifiers and other tools, to shape light. Common constant light sources include everything from incandescent bulbs and LED lights to fluorescent, tungsten, and plasma lights, among others. Only large, studio-centric options can provide lighting power that’s comparable to flash units, but they will work in many scenarios and have proven a go-to for videographers.

Now that we understand what each light source is, we can look at important similarities and differences between flash vs constant lighting as they relate to photographers.

Flash vs Constant Light: Similarities

To begin our journey into exploring flash vs constant lighting, let’s take a look at a couple key similarities between these two light sources and consider how they can benefit your photography.

Quality Light Source

flash vs constant lighting quality advanced off camera flash 02

Both flash and constant lights give us the ability to beautifully illuminate our subjects. Unbound by the limitations of natural light, we can put these light sources to work in-studio or on-location to consistently paint our subjects in quality light. You may find you have a preference for one over the other in certain situations, such as using a constant light in dim lighting when time is of the essence, but the deciding factor won’t hinge on which light source looks “better.” Each can be modified to shape light and achieve equally refined, high-quality results, which brings us to our next point.

Light Modification

One of the best parts about moving beyond natural light and introducing additional light sources is the versatility it brings to the shoot. We become less confined by existing lighting conditions and have countless directions we can go. Lighting modifiers allow us to take it even further.

flash vs constant light profoto b10 modified snoot
Profoto B10 modified with a snoot for a pin lighting effect. See the full technique here.

Depending on the brand you use, there’s no shortage of light modifiers available for your flash or constant light units. For example, Profoto offers over 120 light shaping tools that can be used interchangeably across many of their units, including beauty dishes, umbrellas, softboxes, gels, and more. The added power of flash allows it to punch through some modifiers more effectively than constant lights, but both light sources can be modified for color and light quality.

Flash Vs. Constant Light: Differences

Now, let’s jump into the differences between flash vs constant light.

WYSIWYG vs Trial and Error

flash vs constant lighting light patterns
Lighting Patterns (Left to Right): Flat, Butterfly, Loop, Rembrandt, Split

If you’ve never heard or seen the term WYSIWYG, it means “what you see is what you get.” One of constant light’s biggest advantages is that it takes the guesswork out of knowing where or how the light is going to fall on your subject. What you see in-camera in terms of lighting, lens flare, bokeh, and so on, especially when using live view, is exactly what you’re going to get when you snap the shutter. This can prove especially useful when you’re learning how to position your light for different lighting patterns (e.g., butterfly, Rembrandt, split, etc.).

A number of modern flash units include a modeling light that provides a low-power preview of where the light will fall, mostly for focusing purposes, but it’s not usually bright enough on its own to serve as a full-functioning constant light. One of the exceptions here would be Profoto’s B10X and B10X Plus, both of which offer a maximum output of 3250 lumens (one lumen is as bright as a single candle). That’s a considerable amount of light, especially when focused, and can get the job done in many situations.

If your flash doesn’t provide a similar level of constant light, your setup will likely require a bit more trial and error before locking in your placement and power settings. Of course, the more you practice and familiarize yourself with your flash gear, the easier and quicker this process will become, regardless of the specific gear you use.

Practical Power when Using Flash vs Constant Light

golden hour photography
Golden hour look re-created using Profoto B1. See how I got the shot here.

Simply put, the power output from flash units far exceeds that of constant lights. For this reason, photographers typically use flash to add light while shooting outdoors in bright daylight conditions. For those concerned about recycling times, highly portable flash units like the Profoto D2 (available in 500 Ws and 1000 Ws) can fire up to 20 flashes per second, so you’re not going to miss any important moments. Large productions might have the financial means to purchase or rent giant, Hollywood-style 5K constant lights for this purpose, but most photographers cannot afford such a setup. Luckily, because of the accessibility and power of flash, they don’t need to.

Additionally, as the name suggests, constant lights also require a constant power source. Even with a battery option, then, heavy usage can lead to shorter battery life, which is worth considering.

Freezing Motion

freeze action advanced off camera flash

Flash offers the ability to freeze motion while constant light does not. The reason for this is that you’ll need considerable light output in order to illuminate your scene enough to use fast shutter speeds (e.g., 1/1000) required for stopping action.

Subject Reactions with Flash vs Constant Light

We almost always want the light we add to a scene to flatter our subjects. I say “almost always” because there are always exceptions. With this in mind, it helps to know that bright constant lights can tend to make people squint or blink versus the quick pop of a flash. So long as your subject isn’t staring directly at the flash, which would affect subsequent shots taken after the first, you won’t get the same squinty reaction.

Recommendations for When to Use Flash vs Constant Light

Now that we understand the similarities and differences between flash and constant light, we’ll recap how each light source can best serve you and share our recommendations for when to use each. These recommendations reflect our preferences and may vary from your own depending on your style and goals.

Indoors or Darker Environments: Constant Light

It’s nice to use constant lights so we can see what we’re getting and move a little quicker. As we mentioned above, constant light allows you to see the results in-camera and removes much of the guesswork for setting up your lighting. The modeling light on many flashes will only help for focusing purposes, and it can take time to experiment and dial in settings before reaching your desired exposure. This becomes a bigger issue when shooting against rushed timelines, which happens often during events like weddings.

wedding photography groom

That said, if you take the time to understand how your flash will perform in indoor or lower light conditions, you’re not talking about a huge difference in time between using one light source over the other, especially if your flash is easy to operate.

Outdoors or Situations When More Power Is Needed: Flash

When shooting outdoors, especially during daylight, your only real practical option is flash. As an example, Profoto’s B10X Plus offers 500 Ws of power, which translates to roughly 10x the amount of light you’d get from a standard speedlight, and it’s only the size of a large lens. For situations that require less power, you can use smaller flash units as well, like the Profoto A2, which is only the size of a soda can, yet it yields up to 100 Ws of power and recycles in 0.1 to 1.6 seconds, depending on the power level.

flash vs constant lighting outdoors

Having access to highly portable power like this will help in a few key ways. First, the compact size will allow you to pack light and take your lights anywhere, inside or outdoors. Secondly, flashes pack enough punch to overpower just about any existing light you might run into, including harsh sunlight. You can kill more ambient light with this level of power, enough to make day look like night while still exposing properly for your subject. And finally, with more power comes the ability to use bigger modifiers and get more light coverage from longer distances, which will help you control light falloff and make the transition between light and shadow as harsh or smooth as you want it to be.

On top of all this, newer wireless flashes and triggers are generally easy to use, requiring minimal time to learn how to operate.

A Quick Note on Balancing Budget Vs Quality

We would never recommend going beyond your budget when purchasing new gear, but we also believe it’s worth investing in the best gear you can afford to meet your needs. For example, in terms of purchasing new lighting gear, you will find various brands with products that offer similar features but come in at noticeably different price points.

While it’s tempting to just go with the less expensive option, it’s important to remember that doing so often comes at a cost. Namely, higher quality (and often more expensive) gear will typically deliver more consistency in terms of avoiding misfires, delivering up to a 10-stop light output range, providing accurate daylight white balance and a sustained use of output, not to mention the higher contrast displays and overall sleeker style. All of these points can impact your shoots and will become a bigger issue the more you rely on your gear for professional work (with professional expectations from your paying clients).

Conclusion

I hope you enjoyed this article outlining the benefits of using flash vs continuous light. In simple terms, it helps to remember that constant light offers “WYSIWYG” shooting while flash offers more power (enough to overpower the sun) and the ability to freeze action. Select new flashes are beginning to double as constant lights as well, giving you more versatility out of a single light unit.

As a photographer, you’ll more often turn to flashes rather than constant light to maximize your creative control, but continuous lighting still has its place. There are times when you won’t “need” to use flash OR continuous light, but that’s no reason to put off owning and using flash gear. Regardless of the gear you use, we always recommend that you take the time and find resources to help you learn how to use flash to push your creative potential forward. Doing so will open new opportunities in your photography journey.