I did a quick search but the search term 'multiple' really confused things.

I was shooting some Mountainbiking today and was using a 580ex with some flashwaves triggers for just a little off camera light to show the eyes of the riders - it didn't need much power - I was at 1/16 and 1/32 much of the time.

Because of the nature of one of the corners I was on, I was shooting in short bursts and noticing that the flash was almost able to keep up (well - about 5/8 of the time I guess at 1/32)

This got me to thinking... Is there a product out there that will take a flash trigger and then distribute the output to multiple flashes in cyclic order? This way I could have 2 or 3 flashes on a bar, and fire away at 8fps and the flashes would fire like this...

1,2,3,1,2,3,1,2,3 (etc)

The theory is that with only 1/3 duty cycle, I'd be pretty likely to be able to get 8fps reliably lit.

I did a couple of quick searches but couldn't find anything. Because I'm doing nothing with ETTL etc and it's a dumb trigger, I can't imagine that it would be too complex a circuit - but if something is available then I'd love to know about it rather than re-invent the wheel.

Cheers - Neil G
www.nzsnaps.com

I think pocketwizard multimax can do this.
I haven't tried it since I only have one multimax and the rest are PW II's. Here's an excerpt from the manual:

http://www.pocketwizard.com/upload/photos/300MultiMAX_US_English_Manual_-_Firmware_7xx.pdf

D: SpeedCycler - TRANSMITTER – /MENU A D
Enables SpeedCycler mode. Use this mode to rapidly cycle
through remote flash units and trigger faster than a single
flash can recycle by using multiple flash units. It can also
be used for triggering remote cameras sequentially.
This mode only works with Quad Triggering channels (17
and higher) and two or more MAX or MultiMAX units (set
for RECEIVE mode).
1. From the main screen press /MENU A D to
enable SpeedCycler mode on a MultiMAX (set for
TRANSMIT mode)
2. Enable two or more remote zones
3. Set each MultiMAX (set for RECEIVE mode) to a
different zone
4. Trigger the MultiMAX (set for TRANSMIT mode). The first trigger will fire the first
zone selected, the second trigger will fire the next zone selected. The display indicates
the next zone to trigger with an arrow. Only the zone just triggered will display proper
confirmation



I'd use this feature also

D: Fast Mode - RECEIVER – /MENU A D
The MultiMAX is designed to sync cameras and flash units at
shutters speeds up to 1/250th for most focal plane shutters (35mm)
and 1/500th for most leaf shutters. Some camera and flash
combinations are capable of fast sync speeds up to 1/1000th. The
MultiMAX (set for RECEIVE mode) is capable of operation at these
speeds in Fast Mode. Check your camera’s and flash unit’s manuals
for the maximum sync speeds allowed by your equipment.
A MultiMAX (set for RECEIVE mode) in fast mode will show FAST MODE on the display. While in
this mode Quad-Triggering and Relay Mode are not available and the A B C D L keys perform no
function on a RECEIVE unit. A MultiMAX (set for TRANSMIT mode) will trigger RECEIVE units in
FAST MODE with any remote zone selected, but will perform confirmation only on zone A.

I agree that you should be able to do this with a MultiMax, but you would need at least 3 MultiMax units to make it work (camera, flash A, flash B). It might be less expensive to get a an external battery to recycle the flash you have faster.

I think Bron's can be "ping ponged" without a multimax.

Brent Ward wrote:
I think Bron's can be "ping ponged" without a multimax.

I know, what a bargain ey?

yup, multimax can do it with speedcycling, basically using the quad zones, so u can cycle between 4 different lights.

Silly me though, I forgot to mention...

why not, rather than say.. 2 or 4 lights alternating... have 2 or 4 lights packed together and strung to one trigger, and have them all shoot at one or two stops lower

so instead of Light A B C D alternating at 1/16th power each, have them each going at 1/64th power. The output would be the same as 1 light at 1/16th and recycle times would be fast because each one isn't putting out as much juice.

Max

PShizzy wrote:
Silly me though, I forgot to mention...

why not, rather than say.. 2 or 4 lights alternating... have 2 or 4 lights packed together and strung to one trigger, and have them all shoot at one or two stops lower

so instead of Light A B C D alternating at 1/16th power each, have them each going at 1/64th power. The output would be the same as 1 light at 1/16th and recycle times would be fast because each one isn't putting out as much juice.

Max

Thanks for all the suggestions guys...

I didn't know that the PWs could do this, but as has been pointed out - not cheap :-)

The idea about just having multiple flashes shooting at a lower output is a very elegant suggestion... I'll definitely give it a try to see what my 580ex can keep up with at (say) 1/64...

[edit - Just tried and got 30 consecutive flashes with a 580ex on a 1d2 shooting jpg at 8fpd (MF, Manual mode, manual flash at 1/64)... Shooting 1/32 I got 11 before it missed a flash... The batteries are NI-MH 2400mah and already had a day of shooting on them. Looks like this method is a goer :-) ]

As for my originally suggested method - I spoke to a friend of mine that's built quite a few circuits for timing systems and he thought it would be a trivial job once he verified the trigger from a flash remote with a scope - he thinks it would be $20 worth of components and a couple of hours work...

So if the multiple flashes at once doesn't work, I'll look into getting something made.

Cheers - Neil Gardner
www.nzsnaps.com

Trying to sync separate flashes to the camera shooting speed would be doable, but unnecessarily complicated.

A hot shoe flash works by switching off the current to the flash head, allowing the unused potential to be saved for subsequent shots. In the interval between shots the current flows into the capacitors to recharge them. When shooting at 8 fps the flash will not have the opportunity to recycle so the limiting factor to the # of flashes is how much potential the capacitors can store and how the power is metered out via the manual power setting or ETTL metering.

Shooting in M mode at various power levels (1/16, 1/32, 1/64) will give you an idea how many shots you can fire in succession at 8fps at each power setting and still maintain correct exposure. Canon flash has a "quick flash" mode that will allow the flash to fire at less than full charge, so its not a matter if the number of flashes, but how many of them will produce correct exposure. A bit of testing on your part should provide the answers.

Theres a saying that you don't want to bring a knife to a gunfight and what you have here is a similar situation. Hot shoe flash is really not the best tool for the job the way you want to perform it, because its just not engineered to perform that way. So you might also want to consider changing your shooting approach when using flash.

Shooting in "machine gun" mode at 8fps with a shutter speed of say 1/1000th sec. means the odds are really only 8 out of 1000 (1 to 125) you will capture the "decisive moment" in the action. WIth a bit of practice you'd have no problem capturing the peak of action in anything repetitive and predictable. For example capturing a golf shot at the point of impact is just a matter of pressing the shutter when the arms are about level in the downswing. The result isn't always perfect, but the odds of success are better than 1 out of 125.

Also with flash you have the option of either freezing the action in mid-air like an ice cube, or using second curtain sync (with a single flash) to freeze the action but with a blur trail behind to convey a sense of movement in the still photo. Since you can only used a single flash with second curtain (using the camera only) you'd want to find a shooting position where the ambient light is behind the subject providing rim lighting, with the flash on a bracket (for more natural direction of the light) providing fill.

Another option with second curtain mode is drag the shutter and pan the camera. That's a good strategy when you want to isolate the subject from a distracting background because it blurs the background.

Look beyond the technical goals and solutions to the broader goal of how best to convey the feeling of a mountain bike careening down a track in the woods and you might conclude freezing it like an ice cube 8 times per second isn't the best strategy

Chuck

Thanks for the very considered response... I had forgotten about the quick flash potential so I'll have to have a proper look at the images to make sure that they were indeed exposed correctly.

As for the suitability of flashing a mountainbike, I agree and I'm really not into freezing the action at all... The specific requirement I had in mind for this approach was simply to add a tiny bit of light to either illuminate the face under a helmet visor, although it would work where I also use flash to illuminate the rider and leave the background to just be lit by ambient.

Here are a couple of shots where I could see having a reliable 4-5 consecutivelow power flashes helping me out. Sorry for the watermarks - this is just a quick illustration.

The first image is lit significantly by the flash and is under tree cover. The second is in bright sunlight and again the flash is lighting pretty much the whole biker. The third image however is pretty much just illuminating the face and adding a little bit of pop to the front of the rider.







More photos here if you're interested:
http://nzsnaps.com/Mountainbiking/2009-Gravity-Canterbury-DHMTB2/10243822_5FFpC#P-1-15

Regards
Neil Gardner
www.nzsnaps.com

Chase Jarvis has done something you are talking about and has described it on his blog. Cool videos He did not use multiple strobes (well he did but not in a cycle way you describe above). He was succesful shooting 8fps with Broncolor strobes firing on 60% power of the generator. Pretty sick! (i know budgets )
You can check out his testing procedure there as well, may help you somewhat.