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Tip of the Week – Controlling Power on a Profoto Pack, Part I

Tips & Tricks
The Profoto Acute2R 2400

The Profoto Acute2R 2400

Every week, we post a photography-related tip on our blog. These tips are typically inspired by questions we get from our customers. Sometimes we might feature a technique tip, and sometimes a gear recommendation. If there’s something specific you’d like to see in this section, let us know. Email us at [email protected]

When it comes to studio strobes, thing fall primarily into two categories: monolights and pack/head systems. Each has distinct advantages and disadvantages, and depending on your needs, you may need one or the other at different times in your photographic journey.

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A quick primer on the two: monolights, like the Paul C. Buff Einstein E640, are simple, self-contained studio strobes where the power pack is built into the strobe’s body. The controls for light output and other functions are on the head itself, and all you have to do is plug it into a standard power outlet.

Pack and head systems, on the other hand, separate the strobe head and the power pack (or generator). The head is simply a flash bulb and modeling lamp inside a housing that connects to an external pack, which does all of the power control and distribution for the system.

The thing is, those 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.

Yet those power packs are, as I said, confusing. Take a look at the Acute 2R 2400 below.

The Profoto Acute2R 2400 Ws pack.

The Profoto Acute2R 2400 Ws pack.

The first time I looked at it, I was confused. I was so used to either the White Lightning or Einstein monolights, I kept looking for a single adjustment to control the power output of the head.

To make matters worse, this one pack can accomodate three heads. How on earth, I wondered, are you supposed to tell each head what power to fire at?

The Profoto manual does go into this, but it’s a little… obtuse, in my opinion. So I decided to break things down for you.

In Part 1 of this tip, we’re going to look at how to control the output of the Profoto Acute2R 2400 with just one head connected to it. In Part 2, we’ll look at adding additional heads to the power pack.

Let’s start with the picture below. On the Acute 2R 2400, power is controlled by flipping and turning the switches and dials in the red box.

Power control on the Acute 2R 2400

Power control on the Acute 2R 2400

Let’s start with full power. At its maximum capacity, the Acute 2R 2400 puts out a staggering 2400 watt-seconds (Ws) of power. With one head connected, everything goes to that head. To achieve this, adjust the switches as follows:

  • Full Power
    • First Switch (labelled “A”): top position.
    • Second Switch (labelled A<->B): top position.
    • Third Switch: irrelevant for now.
    • Dial: Irrelevant for the moment, but leave it at “Max.”
The Acute 2R at full power

The Acute 2R at full power

To test our output, we mounted a Sekonic light meter (like this one) on a light stand and took a reading.

At full power, 5-6 feet away

At full power, 5-6 feet away

I wasn’t careful when I hit the “Test” button on the PocketWizard, and ended up blinding myself for a good five or ten minutes. As you can see, at about 5-6 feet, we got a reading of f/45 at 1/125th of a second.

No, you’re not reading that wrong. That’s not f/4 point 5. That’s f/Forty Five. f/45. From a single pack and head.

Next up, we take the power down by one stop of light. Here’s what that looks like (the bold type indicates changes from the previous configuration):

  • Minus One Stop
    • First Switch (labelled “A”): top position.
    • Second Switch (labelled A<->B): bottom position.
    • Third Switch: irrelevant for now.
    • Dial: Irrelevant for the moment, but leave it at “Max.”
Acute 2R, one stop below full power.

Acute 2R, one stop below full power.

This actually halves the light the system puts out, reducing your f-stop reading by one full stop.

At minus-one stop, we get f/32

At minus-one stop, we get f/32

At half the power, we still get a pretty phenomenal f/32 at 1/125. That’s one stop down from f/45.

Next, we cut the power by half, reducing the light by another stop. For this, we go with the following configuration:

  • Minus Two Stops
    • First Switch (labelled “A”): bottom position.
    • Second Switch (labelled A<->B): bottom position.
    • Third Switch: irrelevant for now.
    • Dial: Irrelevant for the moment, but leave it at “Max.”
Acute2R at two stops below full power.

Acute2R at two stops below full power.

Let’s take a look at the reading now.

Acute2R at full power minus two stops

Acute2R at full power minus two stops

Now we’re down to f/22, one stop below f/32.

For another one-stop cut, we go with the switches as follows:

  • Minus Three Stops
    • First Switch (labelled “A”): center position. 
    • Second Switch (labelled A<->B): bottom position.
    • Third Switch: irrelevant for now.
    • Dial: Irrelevant for the moment, but leave it at “Max.”
Acute2R at full power minus three stops

Acute2R at full power minus three stops

Another reading on the light meter, and we see we’re down to f/16 at 1/125th of a second.

Acute 2R at full power minus three stops

Acute 2R at full power minus three stops

It’s pretty interesting to note that even after cutting the power down to 1/8 of the pack’s original capacity, we’re still getting a respective f/16. Let’s go down one more stop, to 1/16th power.

For this, we now turn the dial, leaving all the other switches alone.

  • Minus Three Stops
    • First Switch (labelled “A”): center position.
    • Second Switch (labelled A<->B): bottom position.
    • Third Switch: irrelevant for now.
    • Dial: Move it to “-1.”
Acute 2R at full power minus four stops

Acute 2R at full power minus four stops

This gives us a reading of f/11 at 1/125th on the meter.

Acute 2R at full power minus four stops

Acute 2R at full power minus four stops

Finally, one more adjustment and we’re down to full power minus five stops. For this, we just adjust the dial again.

  • Minus Three Stops
    • First Switch (labelled “A”): center position.
    • Second Switch (labelled A<->B): bottom position.
    • Third Switch: irrelevant for now.
    • Dial: Move it to “-2.”
Acute 2R at full power minus five stops

Acute 2R at full power minus five stops

This gives us our final reading of f/8 on the light meter.

Acute 2R at full power minus five stops

Acute 2R at full power minus five stops

As you can see, the Acute 2R gives us six stops of variability, from full power at 2400 Ws, down to about 75ws at the low end. Contrast this with an Einstein at full power, which would give us roughly f/22, or thereabouts.

That is the greatest advantage of the pack-and-head system – the amount of power it’s capable of. BorrowLenses.com rents a few different packs at the 2400 Ws level, and one at the 12oo Ws level. The D4 heads we rent work with them all.

At 2400 Ws through a single head (or through three heads blasting at full power), we get a peak reading of f/45. Most lenses in today’s DSLRs don’t stop down that much and if they do, you’ll run into things like diffraction and other issues.

But all that power can be handy if, say, you want to overpower the sun. We’ll cover that in a future article, but for now, keep in mind that all that power isn’t necessarily overkill for certain applications.

In Part II, we’ll go from one head to two and even three, and you’ll see how to adjust power on the pack to suit your needs.

That’s it for this week’s Tip of the Week. 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.

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Comments

  • [...] the full guide and stay tuned to the BorrowLenses blog for part two of this series, which promises to take you [...]

  • [...] 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 [...]

  • Ayden says:

    OMG. THANK YOU! We use these at my college, and while the studio instruction is good, they don’t seem to fully understand that those of us going from Monolights to Pack ‘n Heads are going to be needing a bit more babying.

    So thanks =]

    • Sohail Mamdani says:

      Our pleasure, Ayden! Part III of this series is going to be the most comprehensive; we’ll be playing with three heads and going more into Asymmetrical power distribution then. Enjoy!

  • [...] part I and part II of the series on [...]

  • Jason says:

    This would be way awesome in a PDF! (hint hint)

  • Barb says:

    I am using Profoto D1 and Sekonic 358L, when I meter at 125 at full power I get a reading of f/22. Okay do I set my camera at those settings, because its way under exposed…very frustrated

  • Jason Joseph says:

    Jason print the page and have it print to PDF. Conundrum solved.

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