Electronic flash is the king of photo booth lighting

Why?

• It overpowers ambient light, so it doesn’t matter (much) if stray light is streaming in from the sun or another light source at the venue.
• It freezes action, because it lasts for such a short time that it mimics a very high shutter speed.
• Your subjects will definitely know when the photo is taken.
• The color of the light is about the same color as daylight.
• Except for the fraction of a second when it actually flashes, it’s not objectionably bright.
• It doesn’t have to be bulky.

That’s when flash is done right.

Inside a home built booth with Canon G-9 Powershot camera, Alien Bee B-400 strobe, CFL modeling light and power strip.

Electronic flash is not always easy to do right

• You will need more cords: a power cord from AC source to the flash, and a synchronization (sync) cord from the flash to the camera
• Not all cameras can be used with flash. Only cameras that have either a PC terminal or a “hot shoe” can tell the flash when you want it to go off.
• You’ll need some kind of modeling light – a continuous light that stays on so the camera can see to focus and the subjects can see what they will look like.
• The inside of your booth gets even more crowded.
• You might have to think, and as a fifth-grader once said to my wife “it hurts when I think.”

What’s the difference between a speed light, an electronic flash, and a strobe?

In everyday usage, the terms are interchangeable. Technically a strobe flashes continuously like stage lighting, but photographers tend to use whichever term they want to.

How does an electronic flash work?

The power supply boosts your incoming voltage – whether it comes from batteries or house current – to a higher voltage. Usually about 330 to 500 volts.

The flash charges up a capacitor, a device that holds a lot of “juice” and can dump it very fast. It takes a few seconds to fully charge a capacitor, and the time you wait for this to happen is the recycle time.

The capacitor dumps its charge into the flash tube, which converts the electrical charge into light. Think of it as “lightning in a tube” because that’s exactly what it is.

And just like lightning this high voltage can kill you. Even the tiny flash guns in disposable cameras have enough power to stop your heart. Don’t try taking flash guns apart.

Shoe mount speedlights fit directly on top of your camera. That’s got its good points and bad points.

Good points:

• They are small
• They hook directly to the camera with no cords
• They will set the camera’s lens opening and shutter speed automatically

Bad points:

• Because the flash tube is small, the light is harsh and falls off dramatically.
• They run on batteries. Good for portability, not for long session.
• The good ones are not cheap. The cheap ones are not good.
• They will set the shutter speed for you and that’s not always good. (see below)

Shutter speeds: When you are setting your camera’s lens opening and shutter speed, you should know that changing the shutter speed has no effect on the brightness of the picture if the flash is the only source of light.

That’s because the length of time that the flash is on is the effective shutter speed. If the flash only lasts 1/2000th of a second, the effective shutter speed is only 1/2000th of a second no matter what the shutter is set to. That’s why strobes are so good at freezing action. When your guests get crazy in the booth the flash freezes them in their tracks.

However cameras with a focal plane shutter – such as a DSLR camera – can’t use flash at all shutter speeds. That’s because focal plane shutters use two curtains, which move top to bottom on modern cameras – the ones that can be used photo booths. Cameras like the Canon and Nikon slrs with live view.

These sample photos were taken with a Canon T5. Your camera may give different results.

at 1/30th of a second

At a 1/60th of second

at a 125th of second

at a 250th of a second (on some cameras, this would be too fast for flash use)

At a 1/500th second part of the image will be blacked out, because there is no one moment when the shutter curtains are completely open.

It’s even worse at 1/1000th.

Speedlight mounted directly on camera. Runs on batteries, sets the shutter speed automatically, doesn’t have a modeling light.

Incidentally, cameras like the Canon Powershot series do not have a focal plane shutter and can synchronize with higher shutter speeds. I’ve taken photos at 1/2500th of a second using flash and flash totally overpowers ambient light at those high speed.

Flash units that mount on the accessory shoe of your camera, such as the one shown here, are usually “dedicated”. That means that the extra contacts on the bottom of the flash exchange data with the camera’s computer, and will automatically set the shutter speed of the camera to a low number such as 1/60th of a second. That gives you safety but also means that your photos may be affected by the existing light. I like to use high shutter speeds.

For photo booth use a studio strobe usually makes more sense. The monolight style has a combined head and power pack, reducing the number of cords and the amount of clutter.

Alien Bee monolight studio strobe

This Alien Bee B400 from the Paul C. Buff company is probably the most popular model for photo booth DIY types. Certainly not the only one on the market, but it’s got a reputation for reliability and plenty of power.

There are less expensive flash units out there, but this is a bad area in which to economize.

Advantages of a monolight:

• Runs on AC – no batteries needed
• Recycles very quickly
• Has a modeling light to show where the shadows will fall and also lets the guests see what they look like. (suggestion – replace the one that comes with your flash with a cool LED bulb if you can)
• Many have a cooling fan, really valuable in an enclose tower or shell

Disadvantages:

• You need both an AC cord for the power and a PC sync cord to connect it to the camera.
• Somewhat bulky.
• Like any other major component of your flash, you need a back-up “just in case”

The trigger mechanism tells the flash when to perform its magic. Usually a cord does the work, but many flash units also have an optical slave trigger, which triggers the flash when it sees another flash. (turn off or cover the optical trigger so other photographers don’t trip your flash at random.)

More about flash cords and hot shoe adapters.

Baby Pin Plates are a rugged and easy way to mount a studio light with a 5/8″ fitting

Most small studio strobes are designed to mount directly on top of a light stand with a 5/8″ diameter stud. One of the easiest ways to mount them to a cabinet is by using a “baby pin plate,” a steel plate with a stud fastened to it. You can screw, bolt or rivet it to your shell.

Pin plates are available with different lengths.

I thought these ramblings about lighting would be over after 3 sections. I was wrong.

Next: reflectors, umbrellas and soft boxes.

In the interests of full disclosure: I’m a member store of the Photographic Research Organization, the company that make ProMaster products. So I’m a little biased in favor of those products.

Blog contributor Chris Lydle