Here’s a question for the audience: when was the last time you manually set up your flash mode? While I can’t see your show of hands, I am willing to bet that the distribution of answers would be almost entirely correlated with working experience.
Especially in professional fields such as fashion, editorial photography, and in documentary and journalist work, flash is indispensable. I know plenty of pros for whom going out on an assignment without a flashgun on their camera’s hot shoe would be akin to leaving their lens at home!
Yet, education on the subject leaves something to be desired. And that’s putting it mildly!
Plenty of beginning and amateur shutterbugs have only a rudimentary understanding of how flash works. Their favorite photo book authors, instructors, and mentors might not even go into too much detail on the subject either. So how, then, is a newcomer meant to wrap their heads around the complicated story behind flash modes?
That is precisely why I dedicated today’s feature to a grand overview of this topic. We will cover everything you need to know in order to configure and personalize your flash setting for each and every shot and to do so without getting a headache!
Why Are Flash Modes Important?
This might sound like a silly question, but do ask yourself: why would you want to mess with flash modes, anyway? Not everyone will agree that mastering flash modes is a necessity for taking good pictures, after all.
Certain fundamentals such as managing shutter speeds and knowing your focal lengths are indispensable for anyone. Still, not every photographer needs to be a jack-of-all-trades. That’s especially true if it doesn’t suit the kinds of pictures they like to take!
While knowing how to use ambient light is essential, not everyone will be as enthusiastic about using artificial light.
On the other hand, there is a chance you may just not have previously realized the vast opportunities that flash modes can offer, and thus never considered how they may add something to your photography.
I used to be a natural light-only shooter myself for the longest time. That is until I discovered the difference that careful use of flash can make in some contexts – such as portraiture and still lifes, to name just two. Eventually, I became much more enthusiastic about using flash as I realized how many possibilities there are to exploit when you know all its various settings and modes!
This is only one reason why I recommend every photographer out there to study the ins and outs of flash. You never know what bit of knowledge may inspire you!
Maintaining Control in High-Speed Photography
There are, of course, plenty of practical advantages to taking control of your flash mode. For starters, high speed photography is one area where taking control of your flash unit can make or break the shot.
When extremely fast reaction speeds are necessary and the difference between a missed opportunity and an award-winning shot is a bat of an eye, you need to make sure that your equipment is set up perfectly long before tripping the shutter.
Perhaps a bit counter-intuitively, manual flash mode control is often the best way to prevent a mishap. In many ways, leaving your flash to fire in its default automatic mode leaves your results up to chance. Without narrowing things down and limiting your parameters a little, you stand a poor chance of predicting what your results will look like.
This is why the right choice of flash modes takes up just as much of the conversation among sports photographers as crucial variables like shutter speeds or metering modes!
Shutter Speed, Aperture, and Their Effect on Flash
Speaking of which, one crucial detail is the intrinsic relationship between your shutter speed and aperture settings, and flash output. Just like the exposure triangle, there exists a certain reciprocity between these. And you can bet that it can have a great impact on your photography!
For instance, you might have already noticed in automatic flash mode how adjusting the shutter speed blows out or tones down the background without significantly affecting your foreground exposure.
Conversely, changing the size of the lens aperture increases or decreases the intensity of exposure in the area of the image covered by flash.
Already in auto modes, this is a great illustration of how exposure settings and flash modes can interact. A smart photographer can use these three settings to selectively dial in light levels for the foreground and background layers.
Flash Exposure Modes Compared
Now then, let’s assess the meat of the issue. Which flash modes are useful for which kind of work? To reach a conclusive stance on that, we first need to understand what exactly we mean by ‘flash modes’.
Contrary to what you may have assumed, there is no one flash exposure setting that determines the behavior of your speedlight. Instead, we are really talking about three different modes: metering/exposure, flash power, and finally sync speed.
Let’s cover these one by one in the following section.
Auto and TTL Flash Modes
If all you have done in the past is use your camera’s built in flash – or an external flash mounted on the hot shoe set to its default program – then you’ve likely been shooting in some kind of automatic TTL flash mode.
TTL flash mode uses your camera’s own through-the-lens (TTL) light meter. In doing so, it can attain the right flash exposure value based on ambient light levels. Simply put, this means you can trust your flash exposure to be just as accurate as the meter readout in the viewfinder.
However, TTL and Auto flash modes are not one and the same, nor are they mutually exclusive. On most flashes, you can switch TTL metering on and off with the press of a button. That’s regardless of whether you are in Automatic flash mode or not.
When disengaged from TTL metering, your flash will attempt to automatically meter for proper exposure itself, independently of the camera. This is essential when using off-camera flash, for instance.
In either mode, ‘Auto’ doesn’t denote a complete lack of control over exposure though! You can still manipulate and adapt the result of your flash metering to your liking by adjusting the compensation dial on your flash unit.
This works just like camera-based exposure compensation. In half or third-stop increments, you can easily adjust the flash power value derived from the meter. This way, you can achieve a variety of different effects and suit the strength of your flash to your needs.
However, automatic flash metering is not the only option at your disposal.
Manual Flash Mode
When set to manual mode, you get to shoot with flash the old-fashioned way. Without fully automatic exposure metering (though still armed with a meter readout both on your camera body as well as the flash unit’s own LCD), you will need to adjust flash power based on factors like aperture, distance to subject, and ISO.
Manual flash output does not follow any kind of object measure of exposure. Instead, it’s expressed in terms of a fraction of the theoretical maximum flash power. Hence, the actual exposure for each setting differs greatly depending on what kind of flash you are using. You will need to be very careful when operating in manual mode with flash for that reason!
Thankfully, photographers of the 20th century developed multiple handy methods, including guide numbers, to make life easier. With the help of these techniques, you can even shoot with manual flash in bulb mode, sans any synchronization whatsoever!
While perhaps not quite as slick or convenient enough for day-to-day use, manual mode remains a great teaching tool. It helps to demonstrate the complex relationship between flash and exposure and can help you attain more control over your results.
Curtain Sync and Its Uses
One of the most chronically overlooked of all flash-related settings, curtain sync plays a crucial role in how any flash exposure turns out.
Yet, it remains rarely discussed. Newcomers are often told to just stick to the default setting without bothering with sync modes too much.
This belies the immensely creative and exciting results you can attain with careful manipulation of curtain sync settings. In fact, I would argue that curtain sync can oftentimes have a more significant effect on the results of your flash photography than the choice between any of the common flash exposure modes alone.
Front Curtain Sync
By default, almost all flash units fire in front curtain sync mode. This means that the moment at which the flash gun fires coincides with the first curtain in your camera’s focal-plane shutter uncovering the image sensor. By the time the second curtain has passed, the flash exposure is already over.
When motion blur appears in images taken using front curtain sync, the subject generally seems ‘frozen’ at the point in time that you pressed the shutter button. You might also notice a distinctive trail seeming to emanate from the subject. This trail will lead from the subject’s position at the beginning of the exposure to the position it had by the time the second curtain closed.
Rear Curtain Sync
Rear curtain sync is a totally different beast. As the name implies, this setting syncs the flash to fire in line with the second, or rear curtain within your camera’s shutter.
The most obvious effect of rear curtain sync is that it completely reverses the visual aspect of motion blur. Instead of ‘snapping’ or freezing a moving subject at the instant of exposure, with a trail indicating its subsequent motion, rear curtain sync shows the subject as it appeared towards the end of exposure, with a blurred trail leading up to that instant.
Sync Speed Settings
It would be all very sweet if you could use any kind of flash sync regardless of your shutter speed. With your flash set to Auto, you would never need to worry about exposure settings while shooting. Unfortunately, it’s a bit more complicated than that in the real world.
Sync speeds, as in the shutter speeds at which synchronization with flash is possible, are not arbitrary. In fact, they’re relatively limited in most digital cameras commonly used today.
By and large, this is due to the way the focal-plane shutter works. At a high shutter speed, the shutter curtains travel so closely together that the frame is only exposed one ‘slice’ at a time. Since there is no single instant where the entire frame is exposed equally, your flash cannot light the scene equally either!
In vertically-running metal focal-plane shutters – the default design to this day – the typical speed where this starts to happen is 1/250. Some cameras and flashes may offer a “high speed sync” setting. This can enable flash exposures at up to 1/500 or a faster shutter speed. It works by firing the flash not once, but many times in rapid sequence during the exposure. In doing so, you can cover the entire frame piece by piece while the curtains are still moving.
Real Unlimited Sync Speeds
But the true holy grail of high-speed flash photography lies in global shutters. There are two kinds of these – leaf shutters such as those you get on Fujifilm’s X100 cameras, and electronic ones as on Sony’s a9 III flagship.
Regardless of whether it’s mechanical or not, a global shutter exposes the entire scene at once. Because of that, there is no limitation on flash sync speeds, and you can shoot as fast as you like! This is why mechanical leaf shutters especially have been a perennial favorite among photographers who rely on flash very heavily for their work.
Utilizing Flash Modes for Maximum Effect
As we wrap up, I would like to leave you with just one little thought. Before you rush over to your desk, grab your flash gun, set it up on your camera’s hot shoe, and begin to go wild with all the settings you just learned the purposes of, do take a moment to be mindful of these things.
No, don’t worry – this isn’t some self-help, new-age advice for 21st-century photographers. Rather, I just mean to touch on the importance of recognizing why we do what we do when we shoot every day. Knowing which setting to dial in at which moment is crucial knowledge.
But if you only memorize the rote steps, you are bound to get lost in the long run when work calls for something more out-of-the-box. And that happens to all of us, regardless of the kinds of pictures we take!
So, in the end, I would like to warmly ask you to internalize not just the new tricks you learned today, but also the rationale and the science behind them. Believe me, it’ll do you good to have both in memory, and it definitely won’t cost you anything either!
Now, you have my permission. Go off and practice some of the new flash mode techniques you just learned! Have fun!