monolights flash duration/sync. need help

[roman_t]

i guess it may discussed before...
i have sunpak platinum 300 monolights and usualy i set shutter at 1/125s and thats enough for studio portraiture but if i need to capture an action or something requireing shutter up to 1/500s i doubt i can sync them at full power. no information found on their flash duration spec. i see brand strobes with up to 1/800 at full power. how they synced if 5d has ss 1/200s x-sync limit?
thank you beforehand

[DC Fan]

Canon DSLR's typically have maximum flash sync speeds of 1/200-1/250. Set the shutter any faster with third party flashes or strobes, such as monolights, and you'll get incompletely illuminated frames.

Canon uses some technical tricks with some of their flashes, such as the 580ex, that allows a "high speed sync" function, but only with those Canon flashes. Some time spent reading a guide to the Canon flash system (http://photonotes.org/articles/eos-flash/index2.html) will help explain this.

[roman_t]

thank you DC Fan for basics. if body should see high sync flash to go over 1/200s i have to use hotshoe flash in hss mode at minimum output (just to be receptable by monolights optical slave) as a master for my strobes. thats it?

[Lotto]

I tried the HSS flash trigger the strobe at full power trick. While that allow the camera to use higher sync speed, it reduces the flash power the camera can record dramatically. So unless you are shooting something is within very short distance, it becomes impractical.

[roman_t]

"So unless you are shooting something is within very short distance, it becomes impractical"
increasing iso would help it?

[Lotto]

I was testing with a AB strobe, if I recall correctly, it was some thing like this: strobe at full power, f16; HSS trick shot, f2.8. You do the math.

[roman_t]

that shot save or deleted - to look how it works.

[funhouse69]

The problem is the way that the shutter works... This is a first curtain / second curtain thing. The maximum amount of time that the whole sensor is open is usually 1/200th to 1/250th of a second. The actual firing of the flash itself is MUCH faster than that.

Usually when you exceed this you will see some dark shadowing or even total black in a section of the image.

Not really sure how you can "Trick" it...

[SkipD]

thank you DC Fan for basics. if body should see high sync flash to go over 1/200s i have to use hotshoe flash in hss mode at minimum output (just to be receptable by monolights optical slave) as a master for my strobes. thats it?The problem is the way that the shutter works... This is a first curtain / second curtain thing. The maximum amount of time that the whole sensor is open is usually 1/200th to 1/250th of a second. The actual firing of the flash itself is MUCH faster than that.

Usually when you exceed this you will see some dark shadowing or even total black in a section of the image.

Not really sure how you can "Trick" it...Roman_T is assuming that there is a way to trigger the monolights with a Speedlite in HSS and use a shutter speed faster than the "max sync speed". You cannot change the physics of a focal-plane shutter. What Roman_T is thinking in the post I quoted above is quite impossible.

The "High Speed Sync" mode of Canon Speedlites is a "trick" in the Speedlites themselves. In HSS mode, the Speedlite does not emit a single burst of light. Instead, it emits a stream of very short pulses of light. This sort of emulates continuous lighting.

It is absolutely impossible to use any ordinary flash source, whether it be a studio light or ordinary hot-shoe flash (one without Canon's HSS capability) - and however it may be triggered - with any SLR (which uses a focal-plane shutter) using shutter speeds faster than the "max sync speed". If you do use an ordinary flash with shutter speeds faster than the "max sync speed", you will see that a portion of the image has a black "shadow" across it starting from one edge of the image.

[Lotto]

I read the "trick" from Stobist, the theory goes like this: the HSS fires before the shutter starts to open, or very close to it, in turn will fire the strobe. What the camera sensor can record is the "left over/duration" from the strobe, one those t1, t5 thing that I will let some of you strobe gurus to explain. "left over ambient" would make more sense. And faster the shutter speed, less of those light is captured.

Some strobes that have longer duration will work better at this, but seemed most the testers agree that the strobe at full power gives most residue power.

I don't really know what's the real world application for the trick, but the strobists would try anything and everything :)

[inthedeck]

So, in the case of 'freezing action,' how would one go about it. Say, a model jumping in a studio setting, and one wants to freeze the action...and 1/160th isn't fast enough, let's say at the widest aperture of the lens? 1/200th would obviously cause a problem, on most cams, unlike the 1Dmk3 which is capable of 1/250th sync.

So, if Roman were shooting a woman, in a studio how would he achieve the shot in which the action was frozen?

[PacAce]

i guess it may discussed before...
i have sunpak platinum 300 monolights and usualy i set shutter at 1/125s and thats enough for studio portraiture but if i need to capture an action or something requireing shutter up to 1/500s i doubt i can sync them at full power. no information found on their flash duration spec. i see brand strobes with up to 1/800 at full power. how they synced if 5d has ss 1/200s x-sync limit?
thank you beforehand
To answer your question, the "1/800 at full power" you are referring to for the strobe is actually the flash duration, or how long the flash is lit up. 1/800 is a much shorter time than 1/200 time that the shutter is open on the 5D. So, while the 5D shutter is open, the flash can go off and then die long before the 5D shutter starts to close. So there really isn't any issue with syncing issue to speak of here. :)

Assuming that the ambient lighting is contributing little to the exposure, a strobe with a flash duration of 1/800 should easily stop any action that requires a shutter speed of 1/500 even if the camera is set to 1/200. If the ambient lighting cannot be ignore, though, then you will have issues freezing the action.

[Jannie]

Also if you are using your strobes at less that full power doesn't the duration become faster, like if my Elinchrom Style 400BX which I believe goes off at 1/800th second, then if I'm able to shoot at 1/2 power it fires off at 1/1600th of a second, not sure that's the right number, I just did the one stop doubler theory.

The camera would still be set at 1/200 but as explained above this short flash duration happens somewhere in the middle of that 1/200 exposure. The only time you'd have trouble with this is if the ambient room light is bright enough to show the blur of the 1/200th of a second and some have used this (Michael Grecco in his new book) to show both the blur of the ambient or available light and the freeze of the strobes all in a single shot, it's pretty neat.

[bobbyz]

So, in the case of 'freezing action,' how would one go about it. Say, a model jumping in a studio setting, and one wants to freeze the action...and 1/160th isn't fast enough, let's say at the widest aperture of the lens? 1/200th would obviously cause a problem, on most cams, unlike the 1Dmk3 which is capable of 1/250th sync.

So, if Roman were shooting a woman, in a studio how would he achieve the shot in which the action was frozen?

I studio it is easy as you can control the ambient. If no or very low ambient flash duration alone will freeze the action. Whether you shoot at 1/100 or 1/250 won't matter.

BTW - I think 1dmk3 is 1/300 officially. My old 1dmk2 do 1/320 no problems. SO I would guess 1dmk3 can go higher than 1/320.

[PacAce]

Also if you are using your strobes at less that full power doesn't the duration become faster, like if my Elinchrom Style 400BX which I believe goes off at 1/800th second, then if I'm able to shoot at 1/2 power it fires off at 1/1600th of a second, not sure that's the right number, I just did the one stop doubler theory.

The camera would still be set at 1/200 but as explained above this short flash duration happens somewhere in the middle of that 1/200 exposure. The only time you'd have trouble with this is if the ambient room light is bright enough to show the blur of the 1/200th of a second and some have used this (Michael Grecco in his new book) to show both the blur of the ambient or available light and the freeze of the strobes all in a single shot, it's pretty neat.

Usually with strobes, the flash duration increases as you lower the power, not the other way around like it is with hotshoe flashes.

[PacAce]

I studio it is easy as you can control the ambient. If no or very low ambient flash duration alone will freeze the action. Whether you shoot at 1/100 or 1/250 won't matter.

BTW - I think 1dmk3 is 1/300 officially. My old 1dmk2 do 1/320 no problems. SO I would guess 1dmk3 can go higher than 1/320.
The 1Dmk3 has a max sync speed of 1/300 only with EX and compatible flash units. With other types of flashes and strobes, it's "officially" 1/250. You wouldn't be able to to set it to 1/300 even if you wanted to when using non-EX compatible flashes and strobes since the shutter speed goes from 1/250 to 1/320 if set to "1/3 stop increments" via the custom function.

[inthedeck]

So Leo, in your opinion, what would be the best way to freeze action in that type of scenario? Would it be feasible, at 1/160th with a 5D? If so, what kind of flash furation, at Full power would that sort of situation require?

[bieber]

So, in the case of 'freezing action,' how would one go about it. Say, a model jumping in a studio setting, and one wants to freeze the action...and 1/160th isn't fast enough, let's say at the widest aperture of the lens? 1/200th would obviously cause a problem, on most cams, unlike the 1Dmk3 which is capable of 1/250th sync.

So, if Roman were shooting a woman, in a studio how would he achieve the shot in which the action was frozen?

In a dark studio, you could use a second-long exposure and still have no issues with motion blur. You have to remember that a strobe goes off in a single moment, for all intents and purposes it's instantaneous. So if your model is lit solely by the strobe, then it's only going to capture the moment that it goes off: there won't be light around at any other time to cause motion blur.

[inthedeck]

Makes sense. So, it's more of a factor of flash duration, versus aperture, or SS. But, the flash duration has to be relatively quick, if that's what I am understanding? Correct?

[bobbyz]

Makes sense. So, it's more of a factor of flash duration, versus aperture, or SS. But, the flash duration has to be relatively quick, if that's what I am understanding? Correct?

Yes as long as ambient is not there or 3-4 stops lower.

[inthedeck]

Thanks Bobby.

So with t.5 or t.1 which one would you want to be 'faster' in terms of ultimate flash duration? I take it t.1 should be the guiding factor, here, when looking for studio flashes? Correct me if I'm wrong...as I don't really know how the 't' values relate to the whole scenario...I'm just trying to understand those values, for now.

Cheers,
Manish.

[bobbyz]

Manish,

What are you trying to shoot?

[inthedeck]

I'm just going along with Romans' thoughts. of freezing action, in a controlled situation.

For example, a woman jumping in a studio. That's as simple as can be, as an example.

Right now, I don't intend to do any of that type of shooting, since I don't have a studio. I'm just a curious person, that's all, so I ask lots of questions, to learn from some of the other members here.

[Lotto]

I only have first hand experience with the AB strobes, and they have no problem freezing the jumper. Like others said, as long as the ambient light is low enough that does not contribute to the final exposure, most strobes will be about to freeze the motion.

A jumping example, single B800 from above in my dark garage. Lost the EXIF, but I always use 1/100-125 for the strobes.

[inthedeck]

Lotto, why 1/125th? Just curious? Thanks for the example. And that's just one single bee, correct? Nothing more...except obviously, the softbox?

[WillMass]

So, in the case of 'freezing action,' how would one go about it. Say, a model jumping in a studio setting, and one wants to freeze the action...and 1/160th isn't fast enough, let's say at the widest aperture of the lens? 1/200th would obviously cause a problem, on most cams, unlike the 1Dmk3 which is capable of 1/250th sync.

So, if Roman were shooting a woman, in a studio how would he achieve the shot in which the action was frozen?

According to Chuck Westfall, of Canon USA, the normal (not HSS) flash duration of a 550EX is on the order of 1/750 of a second. So, depending on how fast the subject is moving, you could set the camera to expose a completely black frame under the available ambient light, and use the the flash to freeze the action. This could also be done with studio lights as their typical flash duration is much shorter. The variable is; How fast is your subject moving.

For indoor horse shows, where strobing the ring is not allowed, I frequently use multiple speedlights in HSS, because at the 1/750th flash duration my subjects have moved about 1/4 inch, thus creating motion blur.

While I'm not certain, I would assume the flash for Canon Flagship flashes is about the same.

[Lotto]

1/125 is just an old habit, it works and stays. I use Canon master/slave setup in manual mode, the max sync speed happens to be 1/125 too. Yes, it was single light with a small softbox.

[inthedeck]

Thanks for the info. Will...and Lotto. Appreciate that. Maybe some day, I'll give it a whirl!

[PacAce]

Thanks Bobby.

So with t.5 or t.1 which one would you want to be 'faster' in terms of ultimate flash duration? I take it t.1 should be the guiding factor, here, when looking for studio flashes? Correct me if I'm wrong...as I don't really know how the 't' values relate to the whole scenario...I'm just trying to understand those values, for now.

Cheers,
Manish.

The t.5 flash duration (of studio strobes) will always be shorter than the the t.1 duration. That is because the t.5 duration is the flash duration from the point where the flash output is 1/2 (50%) of peak on the up swing to 1/2 of peak on the down swing. The t.1 duration is the flash duration from the point where the flash output is 1/10 (10%)of peak on the up swing to 1/10 of peak on the down swing.

Here's an example of a graph showing the t.5 duration (see http://photography-on-the.net/forum/showpost.php?p=5060311&postcount=25 for graph details):

http://photography-on-the.net/forum/attachment.php?attachmentid=251136

Since there is only a one-stop difference between the flash output at peak and the output at t.5 whereas there is just over a 3-stop difference between the flash output at peak and the output at t.1, if the flash duration is required for stopping action, then one should be looking at the t.1 flash duration rather than the t.5 duration.

[roman_t]

thank everyone for your time and explanations. now i know more than than i did yesterday. :-)
manish, thank you for keeping it hot while i was away with my little son (he has his teeth growing - no sleep at night)
i'd check my studio setup wired and wireless for stable 1/200s

[inthedeck]

Thanks Leo. Makes sense now...and my assumption was pretty much congruent with what you stated above. And thanks for the link...I'll have to reread that post, a couple of times...to get it in my head. :lol: ;)

Oh, You're welcome Roman. Whatever I can do to keep the seat warm. :)

[roman_t]

may flashmeter be used to meter strobe flash duration?

[SkipD]

may flashmeter be used to meter strobe flash duration?A conventional flash meter such as the Sekonic L-358 is only able to inform you of the ISO/aperture needed for a proper exposure and does not have a function for the duration of the flash burst.

There may be handheld meters which provide the equivalent of the graph in an above post (amplitude vs time), but I don't know of any.

I would use a recording oscilloscope and a light sensor as an inexpensive solution (I already have the oscilloscope) to do the job.

[PacAce]

A conventional flash meter such as the Sekonic L-358 is only able to inform you of the ISO/aperture needed for a proper exposure and does not have a function for the duration of the flash burst.

There may be handheld meters which provide the equivalent of the graph in an above post (amplitude vs time), but I don't know of any.

I would use a recording oscilloscope and a light sensor as an inexpensive solution (I already have the oscilloscope) to do the job.
If you ever get the inclination to try viewing the flash meter output on an oscilloscope, you can buy cheap photo transistors and photo diodes from Radio Shack. I'd be particularly interested in seeing what the ETTL wireless command flashes look like. :)

[SkipD]

If you ever get the inclination to try viewing the flash meter output on an oscilloscope, you can buy cheap photo transistors and photo diodes from Radio Shack. I'd be particularly interested in seeing what the ETTL wireless command flashes look like. :)Sounds like a project worth putting on the bottom of my rather long list. I'll probably be getting to it after retirement, and that's likely about 4-1/2 years out :rolleyes:.

[tjongkristian]

Actually, there is a flashmeter that can also measure the flash duration which is Broncolor FCM (if I am not mistaken the name).