I need some technical information/opinions re: HSS vs Tail Sync

sk66

sk66

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Steven
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I'm beta testing some new transmitters/receivers which are "supposed" to support Nikon's FP HSS. But I can't get it to work. They do have tail sync with adjustable timing which is nice and works well ("o.k." even at less than full power and higher SS's w/ SB800). So my question is which is "better?"

The way I see it, Tail Sync offers more power for SS's closer to x-sync, but it's more or less a manual fixed power scenario. HSS costs ~ 2 stops right off the bat, but it is TTL. So, if I'm not mistaken neither is "better" in general and each has potential advantages. Since this is for remote off camera lighting, I don't see TTL as being that big of an advantage in most cases.

I'm not all that familiar with Tail Sync/Hyper Sync in general having always had/used Nikon's FP HSS. Is there something I'm missing or have gotten wrong?

Any help is appreciated!
 
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For critical work, proper High Speed Sync wins easily (HSS, or FP-sync as Nikon calls it - very rapid pulsing, only possible with IGBT units). Exposure is perfectly even, with no variation in brightness up the frame, or colour shift. Can be used at any power setting; compatible with auto-TTL exposure control and works seamlessly with normal sync. Pocket Wizard has done some very clever work on this and can boost brightness by a stop or more in some situations (Canon only) by tailoring the burn duration exactly to the shutter cycle time, on a camera-specific basis - check out their pages on optimised HSS and Peak-Hypersync etc (very techy ;)) The only problem with HSS is the loss of effective brightness, though it's broadly similar to the losses with tail-sync.

Tail-sync (tail-hypersync etc) is a crude workaround that works with any flash unit, but results are highly variable. There is always dramatic drop in exposure up the frame (typically three stops-ish from brightest [bottom] to darkest [top] of frame). There is also a colour shift to yellow at the top of the frame that may or may not be too significant. It works best with long-duration flash units, such as a speedlite at full power only, and studio heads at any power (the lower the power, the better). It's useless with IGBT speedlites at lower power settings, as the tail or the flash gets chopped off, and also with faster studio-type heads, such as Elinchrom Quadra with A-head that has a very steep tail decline, though it's much better with the S-head.

Tail-sync performance is also affected by camera shutter characteristics, with faster-moving shutters yielding slightly better brightness from a shorter cycle time (x-sync is a reasonable guide to shutter cycle time). But there is still a dramatic loss of brightness, even with the most benign flash units.

I'm not keen on tail-sync personally, though it can be effective if you work within its limitations. You can moderate the brightness fall-off quite, at least partially, by using the inverse square law to counteract it, ie position the light above the subject, or turn the camera vertical and position the light on the pentaprism side.

PS Tail-sync uses the same trigger moment as HSS, ie fractionally before the first curtain opens.

Edit: I think tail-sync will soon be superceded when more, more powerful IGBT-types units with HSS become available, eg Profoto B1, Phottix Indra 500 etc. It will become an essential sales feature, though the underlying problem is the scanning function of focal plane shutters. A global all-electronic shutter (sensor-switching) can't be far away.
 
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HoppyUK said:
Edit: I think tail-sync will soon be superceded when more, more powerful IGBT-types units with HSS become available, eg Profoto B1, Phottix Indra 500 etc. It will become an essential sales feature, though the underlying problem is the scanning function of focal plane shutters. A global all-electronic shutter (sensor-switching) can't be far away.
Click to expand...

Totally agree, and add the new Jinbei 600 to that list

Mike
 
Thanks.
Richard, that's the kind of information I needed.
mike weeks said:
What settings do you have in the camera for use of HSS?
I have been doing a lot of testing of triggers, flashes with tail (supersync) and HSS just recently. What transmitters? pm me if you want
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The camera settings are fine. The speedlights go into/display FP mode and fire, they just don't sync. (it works fine if the flash is put on the camera instead.

The units are from a company I've never heard of before (Voeloon). They seem well made overall and easy to use (thankfully, because the manual is pretty bad currently). Uniquely, they have an AF assist light and auto/manual zoom control (not that I see that as being a huge benefit). I'm pretty sure the issue is in the translation and what they are calling HSS/FP is actually Tail Sync.
 
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HoppyUK said:
Tail-sync performance is also affected by camera shutter characteristics, with faster-moving shutters yielding slightly better brightness from a shorter cycle time (x-sync is a reasonable guide to shutter cycle time).
Click to expand...
Not quite sure I'm following...
A higher x-sync equates to faster shutter travel? (makes sense)
And wouldn't a higher SS result in a more even exposure? (with the obvious loss of light)
I didn't note a strong unevenness of exposure (D4/SB800) even though I had the light "wrong" in relation to ISL, nothing like 2-3 stops... Is there something I can do to cause it so that I can see what you are talking about? FWIW, I've only done very basic functionality testing on a white BG so far.
 
sk66 said:
Not quite sure I'm following...
A higher x-sync equates to faster shutter travel? (makes sense)
Click to expand...

Shutter curtains travel at constant velocity, regardless of shutter speed setting. The effective exposure is the gap between first and second curtains, that can be as little as 1mm at fastest speeds. A typical shutter curtain takes 2-3ms to run from top to bottom.

And wouldn't a higher SS result in a more even exposure? (with the obvious loss of light)
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With tail-sync, there is always a big drop in brightness from bottom of frame (close to the peak of the flash output) to top (nearer the tail with much lower brightness and more yellow). The exact drop depends on the shutter cycle time, shutter speed setting, flash duration, flash power setting, the nature of the fall-off curve, and exact sync timing moment. Triggers that can adjust timing simply add a delay to the camera signal, that can position the exposure so the shutter cycles though an optimum (ie flatter) part of the curve - at the expense of more brightness lost.

I didn't note a strong unevenness of exposure (D4/SB800) even though I had the light "wrong" in relation to ISL, nothing like 2-3 stops... Is there something I can do to cause it so that I can see what you are talking about? FWIW, I've only done very basic functionality testing on a white BG so far.
Click to expand...

Point camera at a plain wall and bounce the flash off the ceiling to get even coverage and no bright reflections. Use a highish f/number to minimise vignetting and adjust exposure to a mid-grey tone around the centre of the frame using ISO. There will always be a noticeable fall-off in exposure with tail-sync, it's inevitable. I've seen as little as one stop difference top to bottom with a very benign studio head (long flash duration) at lowish power (even longer durations), to more like four or five stops with a fast-duration head.

If you're seeing perfectly even exposure, perhaps you're getting proper HSS after all ;)
 
HoppyUK said:
If you're seeing perfectly even exposure, perhaps you're getting proper HSS after all ;)
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I don't think so.
TBH, I wasn't really looking for evenness of exposure... I'm still stuck on trying to verify what it *is* doing, and what it's *supposed to be* doing (I'm waiting on e-mail response).

If I try HSS/FP w/ the transceiver/flash in TTL mode it fires but doesn't sync. I know the settings are all correct because the flash is indicating FP (if *anything* is not set correctly for HSS the FP is not displayed).

The "HSS mode" on these is separate from the TTL mode and has a timing offset setting (first clue). W/ the transceiver in "HSS mode" I can leave the flash in TTL and it triggers/syncs, but at a significantly reduced power. That's expected but it's too much of a reduction; I'd guess ~ 4 stops (second clue). And it works "better" with the flash in manual at full power. This shouldn't be possible for true HSS, but it could be "forced tail sync." I.e. same sync timing and the transceiver doesn't know/care about the flash mode (third clue). Regardless of the flash mode/power setting the exposure changes with the camera settings... no TTL exposure (fourth clue. And yes, I've made certain it wasn't due to lack of flash power).

Other than some kind of high speed video to verify lack of pulses I don't know what else I can check; but everything sure seems to indicate tail sync. Unless it's some kind of jacked up, excessively low power, HSS without TTL metering; how messed up would that be?

It is possible that the units are meant to have both TTL HSS (which has a sync issue) plus Tail Sync mode (why?); I would never be able to tell from the written material.
 
HoppyUK said:
The exact drop depends on the shutter cycle time, shutter speed setting, flash duration, flash power setting, the nature of the fall-off curve, and exact sync timing moment.
Click to expand...

I've got all of that... and I'm pretty sure you've confirmed what I was thinking.
I was thinking that a higher SS timed optimally would have lower falloff because it's using a smaller (flatter) portion of the curve. I suppose it could even be possible for the peak to be timed so that there was a small gradient on both sides.

I can see why you don't really like tail sync....
 
Other fast triggers have both FP/HSS and tailsync (YN calls it SuperSync and has variable timing), although they're obviously different modes, as they do different things.

The Nikon version is different in this regard though (IIRC) the Canon triggers don't fire via the centre pin in proper HSS mode, whilst SS would be fired by the centre pin (makes it easier to test). I think Nikon use the centre pin for FP sync (making a test more difficult).

Cue Richard either giving me the thumbs up or telling you I'm an idiot.
 
sk66 said:
...

I can see why you don't really like tail sync....
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My 7d, YN622, Safari2 combination is complete pants at tail sync, I'm led to believe the older Safari is a better option (longer tail), but frankly an ND filter is easier to deal with.
 
Phil V said:
Other fast triggers have both FP/HSS and tailsync (YN calls it SuperSync and has variable timing), although they're obviously different modes, as they do different things.
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Just because they can (marketing)?

The Nikon version is different in this regard though (IIRC) the Canon triggers don't fire via the centre pin in proper HSS mode, whilst SS would be fired by the centre pin (makes it easier to test).
Click to expand...
It seems odd to me that they would trigger in some other method; but it would be nice as it would be easy to test.
 
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sk66 said:
I've always put it as ND for static subjects, HSS for freezing motion in brighter ambient, and Tail Sync if that's all you have available.
(and short flash duration for freezing motion in low ambient)
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I only really shoot static subjects with flash, the demands of speed and power put too large a price tag on something I'd have very little use for. A nice toy to have, but nothing I really need.

I should have been clearer about my aim, it's generally just competing with the sun.
 
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Not sure I can help any more then Steven. Only to repeat, tail-sync is very obvious and there will always be some fading up the frame. Have you done control shots at normal x-sync, then compared to say 1/2000sec? Darkened room obviously.

Can you show us that?
 
HoppyUK said:
Not sure I can help any more then Steven. Only to repeat, tail-sync is very obvious and there will always be some fading up the frame. Have you done control shots at normal x-sync, then compared to say 1/2000sec? Darkened room obviously.

Can you show us that?
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I haven't done any more shots/control shots... I'm waiting to hear back as to what it is supposed to be doing before spending more time on it.
I'll update or maybe post a review once it gets sorted.
 
sk66 said:
Thanks.
Richard, that's the kind of information I needed.

The camera settings are fine. The speedlights go into/display FP mode and fire, they just don't sync. (it works fine if the flash is put on the camera instead.

The units are from a company I've never heard of before (Voeloon). They seem well made overall and easy to use (thankfully, because the manual is pretty bad currently). Uniquely, they have an AF assist light and auto/manual zoom control (not that I see that as being a huge benefit). I'm pretty sure the issue is in the translation and what they are calling HSS/FP is actually Tail Sync.
Click to expand...

810RT?
 
Out of curiosity I went and swapped flashes around and got TTL/HSS working on one SB600. I then tried with the SB800 on that transceiver with no luck... I thought "ok SB800 incompatibility." Put the SB800 back on the original transceiver and it started working. I now have it working on three separate flashes/groups.

I didn't change any settings so maybe there is a shoe/connection weakness? Seems firm enough but I'll check into that further. Or maybe a "power up sequence"? That would be odd/annoying but it started working as I was swapping the turned off flashes around with the transceivers turned on. More testing is in order to see if I can replicate the issue.

So they have both TTL HSS and Tail Sync... (and a pretty useless manual; the tail sync mode isn't in there at all).
 
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