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Kenny Nyhus Fadil
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TTL and manual flash fail in completely different places, and a working photographer chooses between them the way you choose between autofocus and manual focus — by knowing which one lies in the situation in front of you.
TTL fires a pre-flash, reads the reflection, and sets the power for you, which is brilliant when the subject and the framing are stable and the scene is average. Manual fires a power you chose and never second-guesses it, which is brilliant when you need the same output frame after frame or the subject is white, black or hostile to a meter. The deciding question is not experience level; it is whether the light needs to be re-measured at all.
If you are still choosing a flash to buy, that is a different article — my photography flash guide and the speedlight buying guide cover the hardware. I assume you already own a flash that does both modes and want to know which to use when.
Through-the-lens metering sends a brief, invisible pre-flash, measures how much light comes back through the lens, and sets the main burst to hit a target brightness. It is the flash equivalent of your camera’s auto exposure, and it succeeds or fails for the same reasons auto exposure does: it is trying to render the scene as an average, and averages are wrong exactly when your subject is unusual.
The pre-flash can catch people out. The pre-flash and the main burst happen so close together that most subjects blink after the pre-flash has passed, but the power decision is already made from a reflection that may itself have changed: a hand moved, a head turned. TTL is fast and convenient and it re-decides every frame, which is both its strength and its weakness.
On the Godox system, TTL uses the flash head’s built-in receiver, so a TTL flash behaves like any brand-dedicated unit as long as the trigger communicates the camera’s metering. Once that handshake works, TTL is genuinely useful for the walking, changing subject it was designed for.
Three conditions break TTL repeatedly. A very white subject, like a bride’s dress or a white product, reflects so much pre-flash that TTL identifies it as already bright and under-powers, greying the whites. A very dark subject, a black coat or a dark dog, absorbs the pre-flash and TTL over-powers, washing out the shadows. It is the same metre-of-grey logic that makes a camera under-expose a snowfield.
Changing framing is the second failure. TTL re-measures every frame, so when you zoom or recompose between shots on a fixed setup, the flash output moves with the framing, and a set of frames that should be identical come back slightly different. For a portrait sequence where consistency matters, that drift is more annoying than any exposure error, because it is invisible until you line the frames up side by side.
The third failure is repeatability itself. Anything you want to reproduce later — a product shot, a lighting diagram you intend to rebuild, a look you are iterating on — is easier when the power is a number you set, not a value the camera happened to pick on a day when the subject was wearing a different colour.
Manual wins wherever the output must be a constant. Set the power, and every frame is lit identically regardless of what moves through the frame, what colour it wears, or how you reframe between shots. That fixed value is reproducible, comparable, and immune to the pre-flash reflection problem entirely.
A fixed power also lets you reason about the picture like a picture. If the subject is a stop too hot, you know exactly what to move because you know the number you set. With TTL, “why is this frame different from the last one” has no direct answer. The camera made a decision you did not see, from a reflection you cannot re-examine.
The cost is setup time. Manual demands a few test frames at the start of every new scene, and that meter-and-adjust loop is exactly what TTL does for you. For a subject that is genuinely moving through changing light, TTL’s willingness to re-decide is worth more than manual’s consistency. This is a trade, not a hierarchy.
Spare batteries are the first thing I replace when one starts to die early in the cold, before any lens or filter.
Here is the test I actually run. Shoot the same frame in TTL, then in manual set to the same output, then in TTL again with a white object introduced into the frame. Compare. If the manual frame and the first TTL frame match and the white-object TTL frame is off, you have a subject that needs manual. If the manual and TTL frames drift apart as you move, you have a subject that needs the re-measuring.
The pre-flash itself is worth understanding as part of the test. On some subjects, such as anyone sensitive to light or some animals, the visible main flash is preceded by a barely perceptible flicker, and the blink arrives exactly on the frame you wanted. Dropping into manual removes the pre-flash and often removes the blink with it. That alone sends me to manual for portraits more often than exposure accuracy does.
You do not have to choose for the whole shoot. A common working pattern is TTL on a key light while you are blocking and moving, then switch to manual once the setup is locked and shoot the keepers. Another is manual key and TTL fill, where the fill only needs to keep the shadows open and does not need to be exact. The modes are settings, not commitments.
The flash I reach for on location is a Godox AD200 Pro, which does TTL, manual and multi via its built-in 2.4G receiver, so switching between the two habits is a menu change rather than a different light. I keep the camera it usually fires from, a Fujifilm X-T5, set to manual exposure so the ambient is not also drifting underneath the flash decision.
As an Amazon Associate I earn from qualifying purchases.
I shoot manual exposure on the camera whenever I mix flash, because otherwise two automatic systems are correcting each other and neither one’s decision is legible. Lock the camera, then let only the flash decide anything.
The risk when you switch from TTL to manual is that the power TTL chose is not the power you would have chosen. Note the displayed power before you switch, set it in manual, then adjust from there — that way the switch is a handover, not a re-shoot. On a well-behaved system the TTL value will be close enough to your target to start.
Going the other way, manual to TTL, is worse because TTL forgets everything you learned. The lighting ratio you built across three heads does not survive a TTL handoff cleanly, because each head re-measures independently. If consistency across a multi-light setup is the goal, stay in manual and adjust the one light that needs it.
My own worst habit here is fiddling. Mid-session I will nudge flash compensation instead of fixing the real problem, which is usually the subject moving closer. TTL hides that cause; manual exposes it. On a fixed setup manual makes me solve the actual problem instead of trimming around it.
If the subject is white or black, or the framing changes between frames, or you need to reproduce the light later: manual. If the subject is skittish, moving through changing light, and the exact power does not need to survive the shoot: TTL. If you are unsure and have thirty seconds: shoot both, compare, and let the frames decide.
An early favour shoot for a friend was her white wedding dress, and I shot the whole thing on TTL because it was “the safe mode” — the dress came back grey in half the frames and I spent the evening in the develop trying to pull white out of data that was never there. Manual at a fixed power would have held the dress. That was the day the mode stopped being about experience and became about the subject.
Test it tonight against a white wall and a black jacket. Set TTL, shoot both, then set manual at a power you chose and shoot both again. The two-mode comparison in your own hand will settle the argument better than any rule, and it takes ten minutes and a wall.
Use TTL when the subject is moving through changing light and the exact power does not need to survive the shoot, because TTL re-measures every frame and adapts. Use manual when the output must stay constant across frames, when the subject is white or black, or when you need to reproduce the lighting later.
TTL reads the reflection of a pre-flash and targets an average brightness. A white subject reflects so much light that TTL thinks the scene is already bright and under-powers, greying the whites. A dark subject absorbs the pre-flash, so TTL over-powers. It is the same middle-grey logic that affects camera metering on snow.
It can. Because TTL re-measures every frame, zooming or reframing between shots on a fixed setup changes the flash output slightly, so frames that should be identical drift apart. Manual at a fixed power holds the output constant, which is why consistency work favours manual.
Yes. TTL fires a metering pre-flash before the main burst, and light-sensitive subjects can blink right as the main flash fires. Manual mode drops the pre-flash so only the main burst fires, which is a real reason to choose manual for portraits even when the exposure would be fine either way.
Yes, and most people do. A common pattern is TTL while you are still blocking and moving, then manual once the setup is locked. You can also run a manual key with a TTL fill. Note the power TTL chose before you switch so the change is a handover rather than a re-shoot.
Next reads: if you want to know which flash to own before you pick a mode, the best speedlights for mirrorless guide covers the buying side, and the full setup is in the photography flash guide.
External references: the Godox AD200 Pro reference and the Sony a7 IV flash interaction page.
TTL fires a pre-flash, reads the reflection, and sets the power for you, which is brilliant when the subject and the framing are stable and the scene is average. Manual fires a power you chose and never second-guesses it, which is brilliant when you need the same output frame after frame or the subject is white, black or hostile to a meter. The deciding question is not experience level; it is whether the light needs to be re-measured at all.
If you are still choosing a flash to buy, that is a different article — my photography flash guide and the speedlight buying guide cover the hardware. I assume you already own a flash that does both modes and want to know which to use when.
What TTL Actually Does
Through-the-lens metering sends a brief, invisible pre-flash, measures how much light comes back through the lens, and sets the main burst to hit a target brightness. It is the flash equivalent of your camera’s auto exposure, and it succeeds or fails for the same reasons auto exposure does: it is trying to render the scene as an average, and averages are wrong exactly when your subject is unusual.
The pre-flash can catch people out. The pre-flash and the main burst happen so close together that most subjects blink after the pre-flash has passed, but the power decision is already made from a reflection that may itself have changed: a hand moved, a head turned. TTL is fast and convenient and it re-decides every frame, which is both its strength and its weakness.
On the Godox system, TTL uses the flash head’s built-in receiver, so a TTL flash behaves like any brand-dedicated unit as long as the trigger communicates the camera’s metering. Once that handshake works, TTL is genuinely useful for the walking, changing subject it was designed for.
Where TTL Fails
Three conditions break TTL repeatedly. A very white subject, like a bride’s dress or a white product, reflects so much pre-flash that TTL identifies it as already bright and under-powers, greying the whites. A very dark subject, a black coat or a dark dog, absorbs the pre-flash and TTL over-powers, washing out the shadows. It is the same metre-of-grey logic that makes a camera under-expose a snowfield.
Changing framing is the second failure. TTL re-measures every frame, so when you zoom or recompose between shots on a fixed setup, the flash output moves with the framing, and a set of frames that should be identical come back slightly different. For a portrait sequence where consistency matters, that drift is more annoying than any exposure error, because it is invisible until you line the frames up side by side.
The third failure is repeatability itself. Anything you want to reproduce later — a product shot, a lighting diagram you intend to rebuild, a look you are iterating on — is easier when the power is a number you set, not a value the camera happened to pick on a day when the subject was wearing a different colour.
Where Manual Flash Wins
Manual wins wherever the output must be a constant. Set the power, and every frame is lit identically regardless of what moves through the frame, what colour it wears, or how you reframe between shots. That fixed value is reproducible, comparable, and immune to the pre-flash reflection problem entirely.
A fixed power also lets you reason about the picture like a picture. If the subject is a stop too hot, you know exactly what to move because you know the number you set. With TTL, “why is this frame different from the last one” has no direct answer. The camera made a decision you did not see, from a reflection you cannot re-examine.
The cost is setup time. Manual demands a few test frames at the start of every new scene, and that meter-and-adjust loop is exactly what TTL does for you. For a subject that is genuinely moving through changing light, TTL’s willingness to re-decide is worth more than manual’s consistency. This is a trade, not a hierarchy.
Spare batteries are the first thing I replace when one starts to die early in the cold, before any lens or filter.
The Test: Three Frames That Tell You Which to Use
Here is the test I actually run. Shoot the same frame in TTL, then in manual set to the same output, then in TTL again with a white object introduced into the frame. Compare. If the manual frame and the first TTL frame match and the white-object TTL frame is off, you have a subject that needs manual. If the manual and TTL frames drift apart as you move, you have a subject that needs the re-measuring.
The pre-flash itself is worth understanding as part of the test. On some subjects, such as anyone sensitive to light or some animals, the visible main flash is preceded by a barely perceptible flicker, and the blink arrives exactly on the frame you wanted. Dropping into manual removes the pre-flash and often removes the blink with it. That alone sends me to manual for portraits more often than exposure accuracy does.
Using TTL and Manual on the Same Job
You do not have to choose for the whole shoot. A common working pattern is TTL on a key light while you are blocking and moving, then switch to manual once the setup is locked and shoot the keepers. Another is manual key and TTL fill, where the fill only needs to keep the shadows open and does not need to be exact. The modes are settings, not commitments.
The flash I reach for on location is a Godox AD200 Pro, which does TTL, manual and multi via its built-in 2.4G receiver, so switching between the two habits is a menu change rather than a different light. I keep the camera it usually fires from, a Fujifilm X-T5, set to manual exposure so the ambient is not also drifting underneath the flash decision.
As an Amazon Associate I earn from qualifying purchases.
I shoot manual exposure on the camera whenever I mix flash, because otherwise two automatic systems are correcting each other and neither one’s decision is legible. Lock the camera, then let only the flash decide anything.
Mixing Modes Mid-Session Without Losing the Look
The risk when you switch from TTL to manual is that the power TTL chose is not the power you would have chosen. Note the displayed power before you switch, set it in manual, then adjust from there — that way the switch is a handover, not a re-shoot. On a well-behaved system the TTL value will be close enough to your target to start.
Going the other way, manual to TTL, is worse because TTL forgets everything you learned. The lighting ratio you built across three heads does not survive a TTL handoff cleanly, because each head re-measures independently. If consistency across a multi-light setup is the goal, stay in manual and adjust the one light that needs it.
My own worst habit here is fiddling. Mid-session I will nudge flash compensation instead of fixing the real problem, which is usually the subject moving closer. TTL hides that cause; manual exposes it. On a fixed setup manual makes me solve the actual problem instead of trimming around it.
A Decision Rule You Can Use Cold
If the subject is white or black, or the framing changes between frames, or you need to reproduce the light later: manual. If the subject is skittish, moving through changing light, and the exact power does not need to survive the shoot: TTL. If you are unsure and have thirty seconds: shoot both, compare, and let the frames decide.
An early favour shoot for a friend was her white wedding dress, and I shot the whole thing on TTL because it was “the safe mode” — the dress came back grey in half the frames and I spent the evening in the develop trying to pull white out of data that was never there. Manual at a fixed power would have held the dress. That was the day the mode stopped being about experience and became about the subject.
Test it tonight against a white wall and a black jacket. Set TTL, shoot both, then set manual at a power you chose and shoot both again. The two-mode comparison in your own hand will settle the argument better than any rule, and it takes ten minutes and a wall.
Frequently Asked Questions
When should I use TTL flash over manual flash?
Use TTL when the subject is moving through changing light and the exact power does not need to survive the shoot, because TTL re-measures every frame and adapts. Use manual when the output must stay constant across frames, when the subject is white or black, or when you need to reproduce the lighting later.
Why does TTL under-expose a white dress or over-expose a black coat?
TTL reads the reflection of a pre-flash and targets an average brightness. A white subject reflects so much light that TTL thinks the scene is already bright and under-powers, greying the whites. A dark subject absorbs the pre-flash, so TTL over-powers. It is the same middle-grey logic that affects camera metering on snow.
Does TTL cause inconsistent frames?
It can. Because TTL re-measures every frame, zooming or reframing between shots on a fixed setup changes the flash output slightly, so frames that should be identical drift apart. Manual at a fixed power holds the output constant, which is why consistency work favours manual.
Does manual flash remove the pre-flash and the blink?
Yes. TTL fires a metering pre-flash before the main burst, and light-sensitive subjects can blink right as the main flash fires. Manual mode drops the pre-flash so only the main burst fires, which is a real reason to choose manual for portraits even when the exposure would be fine either way.
Can I use TTL and manual on the same shoot?
Yes, and most people do. A common pattern is TTL while you are still blocking and moving, then manual once the setup is locked. You can also run a manual key with a TTL fill. Note the power TTL chose before you switch so the change is a handover rather than a re-shoot.
Next reads: if you want to know which flash to own before you pick a mode, the best speedlights for mirrorless guide covers the buying side, and the full setup is in the photography flash guide.
Keep Reading
- Photography Flash Guide: Speedlights, Off-Camera, and Light
- Best Speedlights for Mirrorless Cameras: Flash Buying Guide
- On-Camera Flash Guide for Beginners: Bounce It Right
- Off-Camera Flash Setup Guide: Position and Shape Light
- Photography Lighting Guide: Natural Light, Flash, and Continuous
External references: the Godox AD200 Pro reference and the Sony a7 IV flash interaction page.