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Controlling Power on a Profoto Pack, Part II

Gear Talk
The Profoto Acute2R 2400

The Profoto Acute2R 2400

Last time, we covered how to control the power on a Profoto pack with a single head attached. In this article, we’ll cover the configurations for two heads.

As I mentioned in Part 1 of this piece, these Profoto power packs are a bit… confusing. Profoto is pretty-much the gold standard of the industry, and their Acute2 packs, which we rent, are considered to be the go-to workhorses for many photographers working with Profoto systems – and with good reason.

In Part 1 of this tip, we looked at how to control the output of the Profoto Acute2R 2400 with just one head connected to it. In this part, we’ll look at adding additional heads to the power pack.

The Gear List

First, let’s wrap our heads around the concept of symmetrical vs. asymmetrical power distribution.

On the Acute 2R 2400, when you’re using two heads, you have to decide whether you want the power pack to supply power to the two heads in equal proportions, or in unequal proportions.

When light is supplied in equal, or symmetrical proportions, you’ll basically have two heads putting out exactly the same level of power. You can change the overall power level, but it’ll change identically for each head.

To achieve this, simply plug both your heads into the two ports on the right of the pack, labelled “B” and “C”.

For symmetrical power distribution, use ports B and C on the powerpack.

For symmetrical power distribution, use ports B and C on the powerpack.

Once you’ve done this, you can follow the directions outlined in Part 1 of this series; the steps to change power for one head are the same for two heads in symmetrical distribution, with one exception – where the directions call for change to the “First Switch (labelled “A”)”, make those changes to the “Third Switch (labelled “B”)” .

Most of the time, however, you’ll want to have an asymmetrical, or uneven distribution of power. The Profoto pack can distribute the power so that there is a 2-stop difference in power output between the two heads.

What does that mean? Well, if you measure the output of your full-power head at f/22 at 1/125th of a second, you can reduce the power of your second head so that its reading would be f/11 – a 2-stop difference – at 1/125th of a second.

To use the head in asymmetrical power mode, simply plug your main head into port “B”, and your secondary head (the one that will be lower in power) into port “A”.

For asymmetrical power distribution, use ports A and B on the powerpack.

For asymmetrical power distribution, use ports A and B on the powerpack.

I know, it sounds backwards, but it’ll make sense in just a moment.

Once your heads are attached, you can now start manipulating your power levels.

When you first start, your panel should look like this:

Full Power to both heads

  • First Switch (labelled “A”): top position.
  • Second Switch (labelled A<->B): bottom position.
  • Third Switch: irrelevant for now.
  • Dial: Leave it at “Max.”
The initial panel setup. For the moment, both heads are getting full power from the pack.

The initial panel setup. For the moment, both heads are getting full power from the pack.

Now we’re going to start adjusting the power for the head plugged into “A”. We start with reducing the “A” head by one stop of light. To do this, here are your panel settings.


Half Power (-1 stop) on head in port “A”

  • First Switch (labelled “A”): bottom position.
  • Second Switch (labelled A<->B): bottom position.
  • Third Switch: irrelevant for now.
  • Dial: Leave it at “Max.”
Power on the A head reduced to a half, giving you a 1-stop difference between the heads.

Power on the A head reduced to a half, giving you a 1-stop difference between the heads.

 

Now we’ll increase the ration between the “A” head and the “B” head to two stops

Quarter Power (-2 stop) on head in port “A”

  • First Switch (labelled “A”): center position.
  • Second Switch (labelled A<->B): bottom position.
  • Third Switch: irrelevant for now.
  • Dial: Leave it at “Max.”
Power on the A head reduced to a quarter, giving you a 2-stop difference between the heads.

Power on the A head reduced to a quarter, giving you a 2-stop difference between the heads.

Any adjustments we make beyond this point will affect both heads from this point on, and will be done using the dial. So, if you’re now getting exposures of f/22 on your “B” light and f/11 on your “A” light, this next step will reduce that to f/16 on the “B”, and f/8 on the “A”.

Overall power reduced by one stop.

  • First Switch (labelled “A”): center position.
  • Second Switch (labelled A<->B): bottom position.
  • Third Switch: irrelevant for now.
  • Dial: Move to “-1″ position.
Overall power reduced by one stop.

Overall power reduced by one stop.

Now, you can fine-tine that Bracket dial so that instead of reducing overall power by a full stop, you can go down in 1/4-stop increments. For the purposes of this article, we’re sticking with 1-stop adjustments.

Lastly, we take overall power down to its lowest, -2 on the Bracket dial.

Overall power reduced by one stop.

  • First Switch (labelled “A”): center position.
  • Second Switch (labelled A<->B): bottom position.
  • Third Switch: irrelevant for now.
  • Dial: Move to “-2″ position.
Overall power reduced by two stops.

Overall power reduced by two stops.

Since I was doing my test shots in the BorrowLenses.com front office, I pressed a couple of our front-desk staff into service as models. I put the heads at their minimum power levels with a 2-stop variance between them. They were placed at the classic 45-degree angles to the subject.

Jo Deguzman, our front-desk manager.

Jo Deguzman, our front-desk manager.

Jo Deguzman, our front-desk manager, is a good sport and doesn’t mind jumping in front of the camera for a quick test. You can see some of the light from the head splashing onto the glossy surface of the BorrowLenses.com poster behind Jo. The second head, placed on camera-left, helps open up some of the shadows on the camera-left side of his face. The strobes were used bare-bulb, with no diffusion.

Cherish Ortiz, giving me an exasperated look.

Cherish Ortiz, giving me an exasperated look.

I made Cherish Ortiz, a member of our front desk staff, wait for a while while I threw up a black background. This is the expression on her face when I started wondering if I should add a third head for some separation from that background. It’s her “Are you kidding me?” look.

As you can see, even at their lowest power, these are powerful lights. In all my tests, I had no misfires, no strange color shifts, no unexpected behaviors. Our Profoto packs are well-used and yet, performed liked champs. There’s a reason these lights are considered by many to be among the best in the world; they are tough, consistent, and powerful.

In our last installment in this series, we’ll throw in that third head I was talking about and show you what you can do with three heads and one pack, complete with examples and panel shots. As always, questions and feedback are welcome in the comments below.

 

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Sohail Mamdani is a writer and photographer based in the San Francisco Bay Area. Follow him on Twitter, Facebook or Google+. You can find his portfolio on his website at sohail.me as well as on 500px and Flickr.

Comments

  • [...] Don’t expect a lot of basic explanation of what a Profoto pack is, for example (for that, we’ve got a series in progress for you). While Melissa does dedicate a chapter in the video to the gear she uses, if you’re [...]

  • J says:

    Hey thanks for the post, I have been looking everywhere for some better instructions than what the profoto manual provides. But I am still a bit confused, how can the B switch be irrelevant? If I wanted to have my key light at 900 watts and my fill light at say 300 or 200 watts, what would I do? Also what happens if you switch the middle switch up to the + position as it seems that you never mention this option? Does it make both lights more powerful?

    • Sohail Mamdani says:

      Hi J,

      Flipping the middle switch up to the + position starts distributing power symmetrically (equally) to both lights at the same level and negates the adjustments you make to the A switch.

      I’m not 100% sure why the B switch doesn’t cause the power flowing to the head plugged into the B port, but in my testing, no matter where I placed that switch, even after a few test fires, the reading I got was always the same. My understanding of it was that the only way to lower power to the B head in this scenario is to use the dial on the pack to adjust overall power.

      In your case, if you want your key light to be at about 900 w/s and your fill to be at 300 w/s, you can come somewhat close by setting the A head to half power (which will make it set to 600 w/s), then set the dial halfway between “Max” and “-1″. That will bring the power on the main head down by half a stop (to 900w/s) and will take the power on the A head down to 450 w/s. You can then take the A head down further to 150 w/s by bringing the A switch to the quarter-power setting.

      That last bit confused me at first. If I reduced the A head down from half-power to quarter-power, shouldn’t you go from 450 w/s to 225 w/s? Then I remembered that I had to factor in the additional -0.5 stop set by the dial, which brings us to that setting of 150ws.

      Also remember that you can manipulate the settings on your light a bit more by varying their distance from the subject. A foot or two can take down your reading by 1/2 to 1 stop – that’s the inverse square law at work.

      Cheers,
      Sohail

  • [...] Sohail Mamdani has published part II of their three part series on how to control power on Profoto packs on the BorrowLenses blog. [...]

  • marc says:

    when is the next one in the series….???

  • Nick Mancini says:

    Where is part 3?

  • Omar O. says:

    yea where is part 3?
    and is there a video tutorial of this? i think a video would be great.. :)

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