# Does the flash pulse when <x-sync & hss on?



## Marsu42 (Mar 31, 2013)

I always thought this was self-explanatory, but on the other hand there might be a reason for the Canon hss button and that the flash doesn't auto-enable hss when >x-sync:

If I shoot below the x-sync limit (1/250s on my 60d) and have hss on, does the flash do the usual short high-power x-sync flash or does it do a continuous hss pulse like when shooting with >x-sync?

Feel free to write "rtfm" as long as you give the answer at the same time :->


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## AKCalixto (Apr 2, 2013)

The HSS will be effective only if the shutter speed is greater than maximum flash sync speed and only if HSS is on.


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## Marsu42 (Apr 2, 2013)

AKCalixto said:


> The HSS will be effective only if the shutter speed is greater than maximum flash sync speed and only if HSS is on.



Thanks!


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## wickidwombat (Apr 3, 2013)

privatebydesign said:


> True, below sync speed the speedlite will work exactly the same if HSS is enabled or not, even when using pre 2012 cameras with the 600EX where the advertised sync speed is lowered when using radio.
> 
> This means there is no disadvantage to leaving HSS enabled, well I never thought of a reason to not have it enabled!



if you are using 2nd curtain sync it cant be enabled its one or the other
lots of situations 2nd curtain is more usefull than HSS

I'm usually using one or the other, 1st curtain is the least usefull mode to have the flash set in


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## RGF (Apr 3, 2013)

wickidwombat said:


> privatebydesign said:
> 
> 
> > True, below sync speed the speedlite will work exactly the same if HSS is enabled or not, even when using pre 2012 cameras with the 600EX where the advertised sync speed is lowered when using radio.
> ...



At least on my 5D M3 and 580 if I set HSS I get 1st curtain synch. Design flaw in my opinion. Below X-synch the 1st / 2nd curtain should be obeyed. Above synch speed, go (automatically?) into HSS. At times when HSS is not set, the shutter speed is reduced to synch speed and my images are (grossly) over exposed. Poor design IMO


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## Marsu42 (Apr 3, 2013)

wickidwombat said:


> if you are using 2nd curtain sync it cant be enabled its one or the other
> lots of situations 2nd curtain is more usefull than HSS



+1 - there should be an option to auto-set 2nd curtain sync <x-sync and hss >xsync, I'll do a feature request for Magic Lantern eventually (the devs there don't have flashes yet ).



RGF said:


> At times when HSS is not set, the shutter speed is reduced to synch speed and my images are (grossly) over exposed.



Indeed, my 60d also doesn't to a proper exposure reduction to x-sync but just overexposes - I'd also call this a bug and not a feature.


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## wickidwombat (Apr 3, 2013)

2nd curtain and HSS cant co-exist by virtue of the way they work so its not an error or ommision

1st curtain fires an intantaneous burst at the start of the exposure say 1/10000 sec long
the remaining duration exposes ambient

2nd curtain work the other way that instantaneous burt fires at the last 1/10,000 sec of the exposure

HSS reduces the power but the duration of the flash is extended for the entire duration of the frame so the moving shutters get even exposure of the flash it doesn't pulse

with pulsing you might be thinking of multi mode and stroboscopic flash where the flash fires multiple reduced output bursts at a programmed (by you) frequency for the duration of a long exposure


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## Marsu42 (Apr 3, 2013)

wickidwombat said:


> 2nd curtain and HSS cant co-exist by virtue of the way they work so its not an error or ommision



... but I'd like an option to switch between hss and 2nd curtain sync, with the current system it auto-switches to 1st curtain sync if <x-sync. If you enable the mutually exclusive 2nd curtain it cannot auto-switch to hss.



wickidwombat said:


> 1st curtain fires an intantaneous burst at the start of the exposure say 1/10000 sec long
> the remaining duration exposes ambient



Guess again  ... a full-power flash on Canon flashes like the 580ex is *1/800* long - I was also surprised how slow flash is when I read that, though at normal power outputs it gets faster.



wickidwombat said:


> with pulsing you might be thinking of multi mode and stroboscopic flash where the flash fires multiple reduced output bursts at a programmed (by you) frequency for the duration of a long exposure



And with "pulsing" I meant the hss system (continuous light) which is implemented as a successive series of low-power flash pulses. Sorry it was confusing, I couldn't come up with a better word do differentiate what hss does vs. "Multi-Mode"/strobe flashes.


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## jonathan7007 (Apr 3, 2013)

Why, in your shooting, is second-curtain the most usual/interesting? I think of this mode as required for subjects moving in the dark where ambient light needs to show movement of flash-lit subject more as expected. Hmm, "expected" -- I mean show the time relationship implied by the shot more as expected.

Hard to figure out the right words but I hope you know what I mean... why shoot so often in "second curtain"? Long exposures -- often -- when you have flash(es) set up?

This makes me want to experiment at the next party!


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## Marsu42 (Apr 3, 2013)

jonathan7007 said:


> Why, in your shooting, is second-curtain the most usual/interesting?



In most cases, 1st/2nd curtain sync won't make a visible difference. The advantage of 1st cs is that the lag shutter press -> picture is shorter, but even for shorter exposure times when something is moving a little (like people or animals) 2nd cs might save the shot since the blur looks more "natural".

Problem is you have to enable it every time manually after changing batteries, and as I wrote it's mutually exclusive with hss setting on Canon flashes so unfortunately my experience with 2nd cs is also more limited than I'd like.


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## wickidwombat (Apr 4, 2013)

I got ya and agree being able to set 2nd curtain as default when it flicks from HSS back within x-sync would be a cool option indeed!

I know the full power flash duration is not 10,000 i was just using that as an example, it seems you know more about flash than your original question let on 

for most shooting within x-sync i find 2nd curtain is preferable as the flash fires at the back end the flash exposure is the last data recorded on the image rather than the first and I feel this yields sharper results especially at lower shutter speeds not necessarily long exposures


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## Marsu42 (Apr 4, 2013)

wickidwombat said:


> I know the full power flash duration is not 10,000 i was just using that as an example, it seems you know more about flash than your original question let on



Since I recently read Syl Arena's book you can call me "Flash Master Marsu" or Mr. Smartypants now :->

Edit: I did a Magic Lantern feature request for hss/2nd cs switching: http://www.magiclantern.fm/forum/index.php?topic=5040.0


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## Lawliet (Apr 6, 2013)

Marsu42 said:


> Indeed, my 60d also doesn't to a proper exposure reduction to x-sync but just overexposes -



My old 30D had safety shift, that stopped down until sync speed was ok if required. Did the rip that out?
(That way you lose only the stops from the exessive light value, but don't have to pay the HSS-price, about 40% more flash range)


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