Is Flash or Continuous Light Better for Photography?

Flash vs Continuous Light for photography

Should photographers use flash or continuous light? If there's a contentious issues discussed among photographers, this is it.

You'll find “natural light” vs “artificial light” debates raging all the time, but I think there's more to the issue than often gets discussed.

Video: Flash or Continuous Light?

What's the Difference Between Flash or Continuous Light?

A flash creates a short burst of light. You can't see the result with the naked eye because the duration is too fast for us to perceive.

Continuous light is always on, making it very easy to see how it affects your subject. What you see is what you get.

There are ways to modify the light from flash or continuous light, and we can change our exposure to craft the final result of our photographs.

Flash Lighting for Photographers

Flash or Continuous Light - Speed Light

Flash comes in a few different forms. There are speed lights, like the image to the right. These are small flashes that typically fit the hotshoe on top of your camera.

However, there are different sizes of flashes. Some people refer to larger flashes as strobes, but they all do the same thing, as I mentioned above.

Flashes and strobes put out a short burst of white light when triggered by a signal of some sort. That signal may come from the hot shoe, a cable connected to the hot shoe, a radio signal or in response to another flash that fires.

For the purpose of this article, we're not going to talk about strobes or speed lights. Let's just call them all flashes, because that's what they do.

Here's a quick summary of what you can expect from a flash.

Continuous Lighting for Photographers

When photographers discuss continuous light, it's usually in reference to an electronic device with some kind of light modifier in front.

Of course, that leaves out a lot of other useful forms of continuous light. Basically, any ambient light you see is continuous light that you can use.

Here's a summary of what you can expect from continuous light:

  • Always on
  • May not be as powerful as flash
  • Great for video
  • May be less portable than flash

Exposure Variables for Flash or Continuous Light

Variables are parts of an equation that can have different values. In photography, we deal with variables on the camera to determine the exposure result that we want.

The most basic variables are within the Exposure Triangle, but as we'll learn, using flash adds more variables that we can use to our advantage.

The Exposure Triangle

Most photographers learn about the three variables of exposure:

  • Aperture
  • ISO
  • Shutter Speed

Used with a meter, whether inside the camera or an external light meter, we can come up with a correct exposure.

How do we know which setting to choose for each variable? That depends upon your creative needs or available light. To figure that out, we use the Exposure Triangle.

The Exposure Triangle

Do you want to add motion blur or freeze motion? The triangle lets you know that a faster shutter speed helps to freeze motion and a slow shutter speed allows motion blur.

Do you want lovely bokeh or should everything be in focus? Your aperture is the key to answer that question.

Is noise in your image a problem or are you willing to accept it? Your ISO has a lot to do with that result.

Most of photography is like other aspects of life. Everything is a compromise. When you deal with continuous light, you have to work with the Exposure Triangle to determine which criteria matters most do you.

In cases with electrical lights, you may be able to turn up the power to compensate for the ISO. However, you may also have a light so bright that your subjects squint and have horrible expressions. If you're dealing with still life subjects, that's not much of a problem.

Two Extra Variables for Flash Photography

When you use flash, you can still use the Exposure Triangle. That allows you to get an exposure for everything in your scene at a consistent level, or the correct exposure for your needs.

When you combine flash with the ambient, or continuous light, you introduce two more variables to your exposure.

  • Flash power
  • Flash to subject distance

The advantage of using flash with ambient light is that you can separate your subject from the background by using different exposure values.

With your traditional Exposure Triangle settings, you can slightly underexpose your background scene, and then add a bit more light to your subject with flash.

Why would you want to do that?

The human eye gets drawn to the brightest thing, sort of like a moth to a flame. If you want your subject to stand out from the background, make it brighter. Flash can easily do that in your photos.

Flash Power

Almost every flash has a range of power. Some flashes have more power than others, so we don't truly have a universal metric to quantify flash power. Guide numbers are an approximation, but the jury's out on how useful they are.

When you fire your flash at full power, that's a 1:1 ratio. The next step down is 1:2, a 50% reduction. It continues down at a reduction of 50%, such as a 1:4 ratio.

Your camera's light meter works in a similar fashion. A 50% reduction on your meter is called a Stop of Light, or an F-Stop.

Let's say that your camera exposure is correct with an Aperture of f/5.6. If you increase your flash power until you get to f/8, that's a 50% increase in the amount of light from your flash.

If you move from f/5.6 to f/4, then you diminished your light power by 50%. If you go down two stops to f/2.8, then you have a 75% reduction of power. That's because the 50% reduction from f/4 to f/2.8 is only 25% of the power compared to your original f/5.6 aperture.

Flash to Subject Distance

So where do you measure the power of the flash?

Since light is just electromagnetic energy, it decays as it travels. So that closer your subject is to the light, the more power from the light source hits your subject.

Move your flash away from the subject, and it doesn't get as much power from the light. That's why handheld light meters measure the output of a light from the subject's position. The only measurement that matters is what hits your subject.

There's another useful fact related to Flash to Subject Distance. This one relates to something called the Inverse Square Law. Photographers get hung up on this and often make confusing statements, but let's keep it simple.

The large your light source is relevant to your subject, the softer the light that falls on your subject.

In other words, move your light closer to your subject for soft light. Pull it away if you want harsh light.

Note that they key here is “relevant to your subject.” A 24″ soft box that's 6″ away from your subject is larger relevant to the subject than a 53″ soft box 6 yards away.

Essentials of Continuous Light

Continuous light with soft box

I mentioned that many photographers think of continuous light as something like this image – an electric light specifically designed to provide color balanced light, directed and diffused through a soft box.

These continuous light sources create absolutely beautiful light when you get them dialed in with the right amount of power for your photography needs.

In my experience, they work best for video. I use a pair of LED light panels for continuous light to create my videos. Each of those panels has a soft box to diffuse and direct the light where I want it to go.

For still photography, continuous light can work very well for most things. The problems come in when you need to freeze motion or prevent motion blur. We'll discuss that a bit later in the article.

Sources of Continuous Light

The nice thing about continuous light is that it's mostly free or easily available. There are some specific cases where it's a pain to lug around, but let's first take a look at some examples of continuous light you can use for your photos.

Using Sun Light for Photography

Continuous light from the sun

Sunlight is the most obvious example of continuous light. It's free and it comes around every day.

That said, working with sunlight isn't without its rewards and challenges.

  • Sunlight is free
  • It's constantly changing in direction, quality, quantity and color
  • Weather may interfere with it
  • Modifying sunlight is possible

My wife loves using sunlight for her photos. She used to take photos outside, but a breezy day blowing leaves tends to ruin her set.

Now she uses our dining room table with window light. The problem is that there's a specific time of day when the light is just right for her photos. Too soon or too late and she doesn't get the kind of light that she wants.

Despite the fact that the light comes through the window, she modifies it by blocking light in some parts of her set. If she needs the light to come on the other side of the set, she just turns the table to get the direction of light she needs.

Best of all, there's no setup or tear down of light equipment for her sessions.

Using Reflectors for Photography

Reflector as continuous light source

Remember, a light source is anything that points light at your subject. You can use a reflector to add light to your subject from the other side of your continuous light source.

That's great for adding fill light, some rim lighting or bouncing a different color of light on your subject. A lot of swimsuit and lifestyle photographers may use a gold reflector to bounce sunlight on their subjects and give them a warm glow.

Using Electrical Lights for Photography

Electric light as continuous light source

There are plenty of electric lights that you can use as a continuous source. This little girl has a light bulb, which means you can use lights bought at Target. True, they may not have much power or the color that you want, but it's a start.

I mentioned that I use LED panels for my continuous light sources. You can get larger and more powerful continuous light sources, or you can go downtown and use some colorful neon lights from a store window.

There are a lot of creative ways to find and use continuous light sources for your photos.

Advantages of using Continuous Light

As long as you have light and a camera, you're a photographer. Lose either of those and you're not a photographer.

Continuous light has some wonderful advantages for you to use.

  • You see what you get
  • Highlights and shadows are predictable
  • You have some ability to manipulate the light
  • Continuous light is consistent
  • You can take rapid-fire photos with continuous light

Here's an example of how easy it can be to manipulate continuous light.

Continuous light modifier with bed sheet

This is a behind the scenes photo of an impromptu portrait demonstration. I was on a photo trip to Cuba with Santa Fe Workshops and Joe McNally. He used the bed sheet from a little girl's home just out of shot to demonstrate how to diffuse the light in harsh, midday sun.

Here's an example of the result.

Jesus with Continuous Light Portrait

This is Jesus, one of the farmer on this Cuban tobacco farm. He's on the other side of that bed sheet. The closer Joe brought the sheet to his face, the better the quality of light on his face. It practically glowed on his skin as the sheet came closer.

The idea of a light modifier is to put something between the subject and the light to order to change the nature of light. There's more than one way to accomplish light modification.

Sirous continuous light portrait

This is Sirous, one of the photographers who joined the trip. He's sitting on the bed where we got the sheet used above. I'm photographing him through an open window.

Using window light is a great way to modify sunlight into useful continuous portrait light. It's soft and directional.

Issues with using Continuous Light

Nothing is perfect for everything, and continuous light is no exception to that rule.

The biggest problem is the quantity of light you get from your continuous light source. When using products designed for photographers, like the Westcott TD-5 Spiderlights, I found that they just don't work very well.

These lights just didn't put out enough light to use at a low ISO. As a result, I had to raise my ISO to 1600 for some portraits and I wasn't pleased with the results.

FJ Westcott TD-5 light example

This photo is much grittier than I'd like. That's mostly due to the noise generated with my camera at ISO 1600 to try and get a shutter speed fast enough for me to hand hold for this portrait.

Granted, this is a few years old and that technology just wasn't good. FJ Westcott now sells a flexible LED panel system that works very well, like this Westcott Flex Cine 1×2′ Daylight Mat (Adorama affiliate link).

Jerry Ghionis used a few of these to take my portrait at WPPI a couple of years ago and they worked very well. I was almost blind after standing in front of them for a while, but it's a good product for portait photographers who need to spend time engaging with their subject rather than their lights.

If you decide to use continuous lights for portraits, don't go cheap. You need sufficient power to take your portraits at a fast enough shutter speed, because people move.

With continuous lighting, you may need to rely upon a tripod for stability rather than going hand held, and that limits your mobility.

I still prefer flash for portraits, because it's easier on my subjects.

Essentials of Using Flash

Advantages of Using Flash

We discussed some great reasons to use continuous light, but there are also plenty of reasons to use flash to light your photos.

  • Flash works when you're ready
  • It's easy to move around
  • It's easy to add multiple light sources
  • There are a plethora of light modifiers for flash
  • Flash freezes motion

Remember when I said my wife could only take photos by the dining room window at an optimum time of day? Flash works when you have charged batteries, day or night.

If you like control, flash is your friend. You tell it how much power to use. The direction of light is within your control. So is the quality and color of light.

I have a number of different flashes for different purposes, and I can use them separately or together. Check out my Resources page to see my lighting gear.

I use and recommend Flashpoint lighting from Adorama (affiliate link to Adorama). It's the same product as Godox, but provided with a warranty and support by Adorama. Godox doesn't support the equipment you buy from them.

When I had a battery issue with one of my Flashpoint lights more than a year after purchase, Adorama replaced and shipped it to me for free.

Flash Duration

Flash duration is one of those topics that photographers have turned into a gnarly issue with some cumbersome terms. Fortunately, it's not that hard to figure out.

There are two terms involved, and I'll show you why there's only one you need to worry about.

  • T.1 = time to 90% flash duration
  • T.5 = time to 50% flash duration

Your T.1 time is how long it takes your flash, at a specific power output setting, to deliver 90% of its power. The fastest T.1 time will be at your flash's lowest power setting. As you raise power on your flash, the T.1 time increases.

Why is that important?

T.1 time is important when you want to freeze motion. The faster your t.1 time, the less time you have light on your subject. Therefore, your subject appears to freeze because it doesn't have light for long while moving.

Your camera's shutter speed doesn't have to be fast to freeze motion, since the sensor isn't recording light while the shutter is open, at least not the light from your flash.

Let me show you an example.

Flash lighting mountain biker in motion

This photo is used a slow shutter speed as I panned the camera with the mountain biker moving past me. You can see the obvious motion blur, except on his face.

That's because two flashes with short duration illuminated is face for a fraction of time and kept it sharp, essentially freezing that part of the subject.

Why two flashes? Remember, you get a shorter flash duration at lower power. So if you need more power in excess of the flash duration you need, add another flash to double the output while retaining a shorter T.1 flash duration.

As for the T.5 time, who cares? T.1 is 90% done, which means there's only 10% of time left and that's unlikely to affect your output. With T.5, you still have the same duration to go, effectively doubling the time measured at T.5.

Flash Example Photos

One of the things I like about flash photography is the flexibility that comes with it. If I want the light to be crisp, soft or colorful, it's easy to create a look. That adds powerful storytelling benefits for your photos.

Beauty light with flash photography

This is a beauty shot of my friend Sam. Everything you see here, I lit with flash.

On the front side, I used clamshell lighting. That included a Beauty Dish just above her and a short strip box below her. You can see the catchlights in her eyes reflecting both sources.

Behind her is a 53″ soft box from Elinchrom. I could have used white seamless paper, but then I'd have to light it from both sides. This is a nice shortcut to get a white background with minimal fuss or expense.

Note: You don't have to use light modifiers from the same vendor as your flash. I have Elinchrom modifiers because I used to use Elinchrom lights. The speed ring is the only thing I had to change in order to use these modifiers with my Flashpoint lights.

2 light flash portrait

This is a two light flash portrait. The key light was to his right side, but his helmet blocked the light from getting to his eyes. To correct that issue, we put a reflector on the floor in front of him and fired a small flash straight down. The light bounced up to fill in his face with soft light.

Shelly 3 flash portrait lighting

This is my friend, Shelly. I used a key light coming down on her left at a 45 degree angle. Notice the light on her shoulders?

There are two more lights, each within a strip box modifier, to add that rim lighting.

Using flash allows you to create separation from subject and background. You can also do this with continuous lights if you have the sources available. It's commonly done on video sets.

However, it's often more expensive and cumbersome to do this with continuous lights compared to using flash.

Eliminating Continuous Light from Flash Photography

You may run into a situation when the ambient or continuous light is undesirable. That usually happens when the stuff getting lit is unattractive or boring. Let me show you an example.

Flash with continuous light

Here's a portrait example where I'm using flash to light the model. The light on her looks great, but the background just isn't complimentary at all. It's ugly, boring and pedantic.

So what if I changed my Exposure Triangle to eliminate the continuous light showing in the background?

Flash without continuous light

We end up with a very different result. It's a bit moodier, but I prefer that story to the one where she's in some cheap pool hall.

All I had to do was change the exposure settings on my camera to get a different result.

Blending Flash and Continuous Light

When people start using flash, they often ask how to blend it with the ambient light at a location. There are two major steps.

Background exposure with continuous light

The first thing to do is to establish your continuous light exposure. You can see that we can get a reasonable exposure in the background, but there's no light on out stand-in subject.

Background exposure with continuous light and addition of flash on model

Next, we light our subject so she has the right amount of light coming from the flash. As you can see from the background photo, a person would just be a silhouette if we didn't have a flash.

You may also need to use a correction gel to match the color of light to the ambient light. Sometimes a 1/4 CTO gel will do the trick to give some warmth to the light coming from the flash.

Is Flash or Continuous Light Better?

I hope you've reached the same conclusion as I have with this article. There's no need for the war discussions about light. Use flash or continuous light as you see fit for your photos.

Each has its strengths and drawbacks, but each also provides you with great resources to illuminate your subjects. You just go about creating your photos in a slightly different manner depending upon the result you need.

Light is a multifaceted tool. Choose the tool you need for the result you want.

All Light is Natural Light

One final piece of information I want to share is that all light is natural.

Some people believe that natural light is superior to artificial light, but there's a flaw in that premise. Light is light.

It's all – every bit of it – nothing more than electromagnetic energy within the visual spectrum. It doesn't matter if you get light from the sun or from the light next to your couch. Those photons are all the same thing.

Artificial means “not from nature.” Well, electromagnetic energy, or light, is completely natural. Just because the ignition of the light came from a device made by man doesn't mean the light itself is artificial.

If that were true, a cigarette lighter would create artificial fire and light. That's not how it works.

Is Flash or Continuous Light Better for Photography?


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