# Thread: How to achieve the shortest flash duration with Profoto7a

1. ## How to achieve the shortest flash duration with Profoto7a

I'm new Profoto lighting user. I was experimenting with water splashes using 7a packs and I'm not that satisfied with the results. There is still some motion blur and I was hoping to eliminate it completely with these packs. Am I doing it right?
I just use one head by a pack set at minimum power (A slot at 1/8th of the power). Are there any better solutions, like using three heads (A, B1,B2) in one pack at minimum power, or Only B (one or two heads)?

2. ## Re: How to achieve the shortest flash duration with Profoto7a

I don't know what the shortest t1 time is for the 7a. Is it fast enough to even do what you want?

One solution to explore is the use of the Profto bi-tube head …

It can be plugged into two packs to keep light level up while dialing down the power for each pack in order to get a shorter duration. (This assumes that the 7a pack shortens duration when power is dialed down).

- Marc

3. ## Re: How to achieve the shortest flash duration with Profoto7a

Thanks! I was thinking about bi-tube, too. They claim 1/12000th of a second for this pack, but there must be a catch, I guess. Maybe with bi-tube, although I think a bi-tube gives you double the power, not shorter duration (1/8th of the power times two - two packs).
I would still like to know if one head in slot A dialed down to minimum power is the solution for the shortest flash duration, or there's some other combination.

4. ## Re: How to achieve the shortest flash duration with Profoto7a

IF your 7a is the 1200 Ws version:

Profoto specs say t0.5 durations are 1/12,000 to 1/2,200

Socket A provides a range from 75 to 1200Ws

Socket B provides 37.5 to 600 Ws.

Presumably, 1/12,000 duration is using Socket B set to lowest output of 37.5 Ws. The question is whether that is enough light. If it is, then you are all set.

If not enough light, the Bi-Tube would then provide 75 Ws at 1/12,000 when each of the two leads are plugged into the B socket of two 7a packs at the lowest power level of 37.5 Ws.

Of course, you can experiment with incremental increases in Ws which will increase the duration by micro steps until you find the duration that is too slow, and then step it back. This would give you the most light at the duration that works.

- Marc

5. ## Re: How to achieve the shortest flash duration with Profoto7a

Thank you both on detailed explanation. I'll try socket B only then (Yes, 1200ws packs). Since I have more packs I can build up enough light. Unfortunately, I don't have leaf shutter lenses, but I do have 1/500s on LF lenses I use.
Thanks again!

6. ## Re: How to achieve the shortest flash duration with Profoto7a

Originally Posted by Pics2
Thank you both on detailed explanation. I'll try socket B only then (Yes, 1200ws packs). Since I have more packs I can build up enough light. Unfortunately, I don't have leaf shutter lenses, but I do have 1/500s on LF lenses I use.
Thanks again!
Shutter speed is irrelevant when working with strobes as the only source of light (like in studio), or for high speed, short duration work like you are doing.

The flash duration is faster than any camera's sync speed, especially in cases like you are working with where you are striving to shoot at the pack's shortest duration. In a dark studio, 1/30 shutter, and 1/250 shutter will be the same.

Shorter shutter speeds are of value when trying to control the ambient levels in balance with strobes … primarily outdoors in brighter light.

- Marc

7. ## Re: How to achieve the shortest flash duration with Profoto7a

Right! My bad...I meant to say push the ISO to help exposure if only using strobes because your power will be at the lowest for the shortest duration

8. ## Re: How to achieve the shortest flash duration with Profoto7a

That makes more sense.

If 37.5Ws doesn't allow stopping down enough, or results in an underexposed image, then increasing the sensitivity of the camera can help that … albeit at the price of image quality by using a sensitivity over the base ISO. With most modern digital cameras moderately higher ISOs won't make much difference IMO.

The OP states he has multiple A7 packs, so the other option is the bi-tube/ Twin Head, albeit at a hefty cost for the head (Pro 7 twin head is \$3,300, so I'd rent one before buying).

- Marc

9. ## Re: How to achieve the shortest flash duration with Profoto7a

Thank you guys once again!
Marc, I'm familiar with all you said. I even use a minute long exposures for multiple flashes and special effects in complete darkness, which wouldn't be possible without this knowledge, but I assumed that Johnny overlooked his mistake. Which turned out to be the case.

10. ## Re: How to achieve the shortest flash duration with Profoto7a

Pushing the ISO, while not ideal was just a thought, but depending on your cameras ISO performance might be quite usable and give you several more stops to play with.
Agree with Marc on the Bi-tube.
Depending on the type of "water splashes" photography, sometimes utilizing the strobe as a backlight to freeze the water can have a nice effect whilst utilizing the short duration and low power setting to your advantage. The generous use of bounce could aid with fill light if the shots are relatively tight.

As a side note the ProB4 fires at 30 fps and 1/25,000th if your primarily shooting water action.

11. ## Re: How to achieve the shortest flash duration with Profoto7a

Unfortunately 7A is not know for the fast duration. Bitube in two packs and then dialed down will get you fastest duration with a tiny bit of power. I think you can even go both bitube cables into one pack to get a slow duration and a little power. Other than that you have to go 8A or Elinchrom for truly fast duration.

12. ## Re: How to achieve the shortest flash duration with Profoto7a

Unfortunately 8A won´t help you much unless you need less power (see att. drawing from Profoto). These are all t 0.5 readings which cannot be directly compared to t 0.1 values. In all settings up to about 1/4 to 1/2 power you will be better served with broncolor (grafitA, Scoro or Move). Profoto will have shorter times at full power settings, due to their higher capacitor voltage.
To all makes applies you will nearly half your duration by using twin heads.

Cheers, Ulf