The Acute B2 600 Air S is the smallest battery pack in Profoto’s product line up. It replaces the larger Acute B 600 model in a unit that measures just 19×13.5×20cm and weighs 3.6kg with its Life (Lithium Ion Iron Phosphate) battery. But although it is notable for its compact size and weight, the Acute B Head still packs a punch with its 600J of flash power, and integrates a modelling light that uses a Halostar 65W lamp that delivers the glow of 90W halogen.

I used the Acute B2 600 Air S with an Acute B Head and a small disc reflector that all fit into a small (34×14×44cm) shoulder bag. The bag is made out of heavy-duty nylon and has a high-quality feel, with ample padding. It integrates two rubber feet and a double zipper with a lid that unhinges itself from the side ensuring quick and easy access to the gear.

First impressions of the new pack are what you’d expect from Profoto. It is workmanlike and very sturdy, with no frills or extraneous elements to its appearance or functionality. The battery manages to pack in all the essential features that professional photographers demand from a battery pack in this class, including a radio slave system that uses a Profoto Air Sync hotshoe-mounted unit.

The top of this unit features all the controls laid out in a very logical manner. You have to press and hold the on switch so it doesn’t accidentally get activated and waste the battery life. Once on, it is ready to use in around a second after a battery life LED lights up and a large, bulbous test button illuminates to signal that the power has fully charged up and the flash is ready to be fired at the required power output. The Acute B2 600 has a swift auto dump function to help avoid getting any dud images that may be overexposed when the energy setting is turned down.

The red LED on the top of the unit indicates which radio channel is being used. It is possible to choose one of eight channels to ensure the unit isn’t inadvertently set off by anyone else using the Profoto Air system nearby. The unit also has an IR-cell/slave facility and a sync socket so the flash can be triggered at close quarters with a standard cable or infrared hotshoe unit.

The Acute B2 600 Air S has a single lamphead socket that is straightforward to line up with the 12-pin Acute B Head plug and lock into place by rotating a collar. Adjusting the power is achieved by putting the energy switch to one of three settings – 600J, 150J or 37J. The power can then be fine-tuned by adjusting an adjacent dial in 2/10 f-stop increments. This power range delivers seven usable f-stops from its maximum down to a 9J output.

It is simple enough to get used to this two-pronged switch and dial approach to adjusting the energy output. However, it is not possible to control the power wirelessly via the hotshoe-mounted Air Sync unit, unlike many of its competitor models. Profoto does have an Air Remote unit that enables wireless power control but that function doesn’t work with the Acute B2 600 battery pack. (The Air Remote can still be used to trigger the Acute B2 600 flash).

But what the Air Sync lacks in remote power control functionality, it makes up for with top-notch reliability and ease of use. Setting the channel is simple, but its performance is the most reliable I’ve ever used.

During my tests it never failed to set off the lamphead when the power was fully recharged. Profoto says that it also delivers ultra-short delay to enable the use of the fastest sync times. The company also states that the Air Sync can be triggered from a distance of up to 300m. 

I would think that this applies when there are no obstructions between the Air Sync and the pack, but the triggering distance should prove ample for most photographers’ needs.  I gave it a stern test in a forest where I managed to trigger the unit from approximately 80m away, which is a very impressive feat considering that there was dense vegetation and no clear line of view.

Action shooting
Profoto makes some ambitious claims about the performance of the Acute B2 600 Air S. It can, it says, deliver up to 200 maximum power flashes and more than 12,000 flashes on it lowest power setting, and try as I might, I found no reason to doubt these figures. During my tests on a typical shoot, I fired more than 100 full power flashes (for the cycling shots) and almost 200 lower powered flashes while using the flash as a fill-in light for a model shoot and the pack still registered that the battery had 1/4 power life in it.

It is important to safeguard the battery life as much as possible, and while there is an auto off function to turn the pack off after it has been unused for a period of two hours, you can’t adjust this to put it to sleep for shorter down times. However, it is worth noting that the battery can be kept topped up because it has no memory effect, so there is no need to run it down after usage to preserve its longevity. Conveniently, it can be still be used while charging takes place, and the battery can be rapidly recharged in around 2.5 hours with the Profoto Charger 2A, and it can be removed from the body so that a spare can be slotted in and used to extend shooting times even further.

Recycling times are also swift enough with a 0.08s and 2s performance on minimum and maximum power respectively. Flash duration is, predictably, quicker on the lower power settings, which is worth bearing in mind when capturing fast-moving subject matter to ensure the flash freezes the action.

Shooting on the lowest power setting also means recycling times are almost instantaneous. In fact, on the 9J settings I found I could fire nine frames-per-second (using a Nikon D3s) with the power recharging indefinitely, so that I was only limited by size of Compactflash card and the burst rate of the camera, making it ideal for capturing a decisive split-second moment or a multiple exposure strobe effect.

Most photographers are unlikely to ever need to push it as hard as I did and should find using it more than adequate for lighting slightly less speedy dynamic subject matter, such as fashion model shoots. The recycling times and flash duration, even on the higher power settings, are better than ample. You will also appreciate the rock solid colour temperature performance that hardly fluctuates at all, so it won’t produce any unexpected colour casts.

Conclusions
Battery packs are getting smaller and more powerful, with improved recycling performance, and Profoto’s latest version is top of its class.

The pack’s controls are straightforward, so it doesn’t take long to become self-assured when operating it. It should appeal to any photographer working on location who needs a one-light solution in a package they can throw over their shoulder.

Profoto also states that the battery is tested, certified and licensed to travel and fly all over the world, ensuring that photographers’ creative lighting needs aren’t limited to their own shores. Its robust build quality means most hire centres will snap it up, and it should withstand the most intensive use from demanding photographers.