What Your Speedlite Actually Does
A Speedlite (a portable flash unit that sits on your camera or fires from a stand) produces a burst of light lasting a tiny fraction of a second. Your job is to decide how much of that burst reaches your subject, and most flash photography techniques, from bounce flash to off-camera lighting, come back to that one decision.
Every flash photo mixes two kinds of light. Ambient light is the light already in the scene: daylight, a lamp, streetlights. Flash light is the burst your Speedlite adds. Your camera records both in one frame, but you control them differently:
- Ambient light responds to shutter speed, aperture and ISO, exactly like a photo without flash.
- Flash light responds to aperture, ISO, flash power and the distance between flash and subject. Shutter speed barely touches it, because the burst is shorter than the shutter speeds you’ll normally use (up to your camera’s flash sync speed, explained further down).
That split gives you a trick you’ll use constantly: slow the shutter to brighten the background without changing how the flash lights your subject. TTL and manual are simply two different ways of choosing the flash power.
How TTL Flash Works
TTL stands for “through the lens”. In TTL mode, your Speedlite fires a faint pre-flash a split second before the real one; the camera measures how much of it comes back through the lens, and it sets the main flash power to match.
Think of TTL as cruise control. You choose the speed, and the car handles the accelerator, which works beautifully on an open road. It can’t read the road ahead, though, so it makes the occasional wrong call.
TTL is at its best when:
- Your subject’s distance changes between frames, as it does at parties, weddings and events.
- You’re bouncing flash indoors and need to keep moving.
- You don’t have time for test shots.
It struggles because it aims to make every scene average out to a mid-grey. A white dress that fills the frame fools it into underexposing, and a black suit fools it into overexposing. Mirrors, glasses and glossy surfaces throw back too much pre-flash, so the camera fires too little. And because TTL recalculates every shot, two near-identical frames can come out slightly different.
The fix is flash exposure compensation (FEC), a setting that tells TTL to add or remove flash on purpose. It works in stops, where one stop is a doubling or halving of light. If a subject in a white shirt looks grey, dial in +1 FEC. If a dark scene looks washed out, try -1.
How Manual Flash Works
In manual mode, you tell the Speedlite exactly how much power to fire, and it fires that amount every time until you change it. If TTL is cruise control, manual is driving a car with a clutch and gearstick: more to think about at first, but nothing happens that you didn’t choose.
Power is shown as fractions of full output: 1/1, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64 and usually 1/128. Each step down halves the light, which is one stop. Most Speedlites also let you adjust in thirds of a stop between those steps.
Distance matters as much as power. Move your flash twice as far from your subject and only a quarter of the light reaches them, a loss of two stops. This is the inverse square law, and it explains why a flash 1 metre from a face at 1/16 power lights it a full stop brighter than the same flash 2 metres away at 1/8.
For a person a couple of metres away indoors, 1/16 power is a practical place to start. Take a test shot, check the screen, then move one step up or down at a time. Once it’s right, it stays right, which makes manual the better choice for portraits, products and any setup where the flash sits on a light stand.
TTL vs Manual Flash at a Glance
| TTL | Manual | |
| Who sets the flash power | Your camera, every shot | You, once |
| Consistency between frames | Can shift slightly | Identical until you change it |
| Speed to get started | Instant | One or two test shots |
| Handles changing distances | Yes | No, you re-adjust |
| Fooled by white, black or shiny subjects | Often | Never |
| Best for | Events, moving subjects, quick bounce flash | Portraits, products, off-camera setups |
| What it teaches you | Very little on its own | How power and distance shape light |
So Which Mode Should You Learn First?
Learn manual first. It forces you to understand the two things behind every flash exposure, power and distance, and once you do, TTL stops being a mystery. You’ll know why it underexposed the white dress and roughly how much FEC to add.
That doesn’t mean avoiding TTL while you learn. Split them like this:
- Use manual when you practise at home, light a portrait, shoot products or take your flash off-camera.
- Use TTL at a party or event, where distances change faster than you can adjust.
- Switch back to manual the moment TTL gives you uneven results in a setup that isn’t changing.
Experienced photographers often mix both in one setup, such as a TTL flash on the subject and a manual flash on the background. That comes later, once single-flash work feels natural.
Bounce Flash: Softer Light From the Same Speedlite
Bounce flash means pointing your Speedlite at a ceiling or wall instead of straight at your subject. The light spreads across that surface before it reaches them, so the surface becomes a much larger light source, and larger sources create softer shadows.
- Tilt the flash head between 45 and 90 degrees toward a white or neutral ceiling, ideally around 2.5 to 3 metres high.
- For more shape, swivel the head toward a side wall instead, so the light arrives from one direction like window light.
- Raise the power. The light travels further, and the surface absorbs some of it, so in manual you’ll typically need at least two stops more than direct flash. TTL adjusts automatically, which makes it handy here.
- Check the colour of the surface. A green wall bounces green light onto skin, so stick to white, cream or grey.
Bouncing straight up off a high ceiling can leave dark eye sockets. If your Speedlite has a pull-out white card, slide it up to throw a little light forward and add a catchlight (the small bright reflection that brings eyes to life).
Fill Flash: Using Flash in Daylight
Fill flash is a low-powered burst that lifts dark shadows without becoming the main light. Reach for it when the sun is behind your subject, or overhead at midday, leaving shadows under the eyes, nose and chin.
Done well, nobody notices the flash at all:
- In TTL, set FEC to between -1 and -2. On its own, TTL tries to light the face to full brightness, which looks flat, and pulling it back keeps the daylight in charge.
- In manual, expose for the background first. Then start the flash low, around 1/32, and raise it until the shadows open up but still look natural.
There’s one catch. Bright daylight often pushes your shutter past your camera’s flash sync speed, the fastest shutter speed the flash can keep up with, usually somewhere between 1/160 and 1/250 of a second. Go faster, and a black band can creep across part of your frame. Our off-camera flash guide explains sync speed, black banding and high-speed sync in detail.
Practise Both Modes in a Guided Session
You now know what TTL and manual do, when each one wins, and how bounce and fill flash work. The quickest way to make it stick is to feel the difference on your own camera, with someone beside you explaining what just happened in each frame.
That’s exactly how the Speedlite Essentials workshop at Sydney Photographic Workshops is built. Over five hours in the Alexandria studio, you start with TTL vs manual, then practise bounce and fill flash, flash exposure compensation and balancing flash with ambient light, shooting a professional model or still-life subjects. Groups are capped at eight; the only prerequisite is that you can use manual mode, and SPW lends Speedlites if you don’t own one yet. As one past student, Chris, admitted in their review: “I have been avoiding using my flash unit for too long.”
Once one flash feels comfortable, you can move from our beginner Speedlite workshop to the intermediate level. This is where you take your flash further, with multi-light setups and TTL and manual working together in the same shot.
Frequently Asked Questions
Is TTL or manual flash better for beginners?
Manual is better for learning, because it shows you how flash power and distance control your exposure. TTL is easier for fast-moving situations like events. Most photographers learn manual first, then use both.
What does TTL stand for in flash photography?
TTL stands for “through the lens”. The flash fires a faint pre-flash, the camera measures the light that returns through the lens, and it sets the main flash power automatically.
Why do my TTL flash photos look different from shot to shot?
TTL recalculates the flash power for every frame, so small changes in framing, clothing colour, or reflective surfaces change the result. Switch to manual flash when your subject and light position stay the same.
What power should I start with in manual flash mode?
For a person about 2 metres away indoors, start around 1/16 power. Take a test shot, then adjust one step at a time. Each step doubles or halves the light.
Can I use bounce flash outdoors?
Only if there’s a nearby wall or overhang to bounce from. Outdoors without a surface, use direct fill flash at low power, or take the flash off-camera with a modifier.
Do I need my own Speedlite for SPW’s flash workshop?
No. Sydney Photographic Workshops lends Speedlites to students who don’t own one. You do need a camera with full manual mode and the ability to use it.
