Acratech GP
$400 / £245  www.acratech.net

The Acratech GP

Acratech's ball heads were born out of the frustrations of its founder, Scott Dordick, an avid photographer and engineer, who also happened to run a machine shop for the aerospace, automotive and medical industries. After a fruitless search in the late 90's for a light and strong ball head for hiking, he ended up designing and fabricating his own, using his tools and experience in precision manufacturing. His personal solution became the original Acratech Ultimate ball head, with a unique 45° clamp around an exposed ball.

In addition to this Ultimate head, Acratech Inc. currently produces a full line of other heads, leveling bases, clamps and plates, all at its California facility. Acratech products are characterized by a very efficient, almost skeletal design, while the ball heads in particular have a very slim and open structure that allows dirt and moisture to fall away from the ball and locking mechanisms.

Specifications

Ball diameter   38mm (1.5")
Height  105mm (4.14")
Weight  430g (0.95 lb)
Base diameter  60mm (2.36")
Maximum load  11.4kg (25 lb)
MSRP  $400
Warranty  10 years, worldwide

Design and features

The Acratech GP is visually similar to other Acratech heads, which means it looks like no other brand's products. Not only does the head have an exposed ball and minimal structural enclosure, but the GP (which stands for Gimbal Pan) has an internal axis for using long lenses efficiently, along with the option to flip the head upside-down on a tripod for perfectly level panning.

The GP-series heads come in three sizes, the largest being the GP with a 60mm base and 60mm quick release. This is followed by the GPS (Gimbal Pan Smaller) which uses the same release, but has a 53mm base to fit on smaller, travel tripod platforms. For those who want an even, more compact package, there is the GPSS (Gimbal Pan Still Smaller) which combines the minimal footprint of the 53mm base with a 46mm quick release clamp. Considering the ball diameter for all Acratech heads is a consistent 38mm, these components are really what most affect the size of the product.

Open ball design

Acratech's standard 38mm ball is clamped between two semi-circular jaws, with a U-shaped drop slot opposite the locking and friction knobs. The top and bottom of the ball are completely exposed, which allows dirt and moisture to fall away from the ball, rather than get trapped inside with the mechanics. Coincidentally, this also provides a very broad range of motion for tilting the ball.

Gimbal function

When a long lens is mounted on the head, the drop slot can be used in combination with a rotating lens collar to hold the lens off to the side of the head and tripod. Acratech has included a pin and sleeve system on its GV and GP heads to balance the load across the head, rather than solely in the drop slot. This provides a gimbal-like separation of the rotational axes, and some suspension of the overall weight.

Panoramic flip

Aside from the more pedestrian ball head duties and the extra gimbal mechanics, the GP has a removable quick release to allow the stem of the ball to be mounted, pointing down, directly onto a tripod.

With the camera connection moved to the panning base, the result is a head that can level a camera, and pan while maintaining this perfect horizontal. For multi-image panoramas and horizontal video movements, the results are much better than when the panning base is solely beneath the ball (where it typically resides).

Construction and handling

The superbly finished aluminum that Acratech is known for, on full display.

Once the unusual design of the Acratech GP head has been accepted, the next impression is just how light and solid the head feels in hand. The assembly and construction of the whole head is excellent, particularly where any moving part or gap is concerned. Nothing wiggles or feels insubstantial, and the thickness of the supports and clamps points to a head that will put up with a lifetime of service in rough locations.

When it comes to the finish quality of the head, every aluminum part has the same silken black surface, with gently rounded edges and corners. The slim cradle and clamping mechanism reduce the amount of material needed for the primary functions, and there are weight-reducing impressions and holes even on these parts. The obvious join lines of the rubber knob covers, and the machined stutter pattern on the U-shaped clamp do lessen the visual quality a bit, but the overall aesthetic is function over form, so this is not much to complain about.

Ergonomics

Although the layout of the controls is a bit different from conventional cylinder-type ball heads, the knobs on the GP are actually the same size, and stick out just as far, as the knobs on most other heads. This means they are easy to grasp and turn while a camera is on the head, and the rubber covers over the fluted metal knobs add extra grip when things are wet, or gloves are in use.

With a camera tilted to the left in the drop slot to achieve a portrait orientation (on most SLRs), both the locking knob and the pan knob end up on the right side. So, unless a remote release is being used, this requires some hand gymnastics to lock things down or change the friction amount. When using the head in gimbal mode, the best orientation is to have the drop slot (and therefore the camera and lens) off to the right, allowing the knobs to be easily manipulated by the left hand.

Even with the Acratech GP's unconventional mechanics and design, the ergonomics are not too different from most other heads. While not always the best, they are admirable for how well they work with the various functions and capabilities of the head.

Panorama orientation

There are other heads on the market that can be converted for upside-down operation, and a few are even designed to only be mounted with the ball stem directly on the tripod (such as the Novoflex MagicBall). For most conventional heads, the standard quick release clamp needs to be replaced with a panning clamp to achieve a perfectly level pan after adjusting the ball, but this duplicates the panning functions and adds significantly to the cost. The Acratech GP provides the option for this inverted operation without any additional parts to buy, or an aftermarket solution of questionable stability. The laser-engraved degree markings are even conveniently mirrored, for precise pans in either orientation.

The only minor problem in the system are the positioning studs on the bottom of the GP-series quick releases. These prevent rotation on the specially-designed stem of the ball, and provide more physical space for operating the clamp when it's mounted on the panning base. Unfortunately, the lack of any matching alignment holes on the panning base means that the clamp can potentially rotate on its own if not seriously screwed onto the panning base.

Any unintended rotation could mess up a panorama or other fine framing, and some minor indentations on the bottom of the base could prevent this.

Optional lever release

Acratech's adjustable width, lever-action quick release platform.

Almost all higher-end tripod head manufacturers offer the choice of either the traditional screw-knob quick release platform, or a faster lever-action clamp. Aside from the speed of operation, the main functional difference is that most lever designs only close to a specific width, which can make using plates from various manufacturers (all with slightly different ideas about plate sizing) a dubious affair.

While many manufacturers include a way to adjust the lever to accommodate differing plate widths, Acratech has instead combined a screw knob clamp with the lever clamp to allow for an almost-universal plate fit, along with very quick equipment changes. This double-sided clamp makes it much easier to adjust the width, without the need to turn a tiny screw or hidden cam within the lever itself. However, it also means a less-than-confidence-inspiring gap on the clamp at both ends. At least with other lever releases, one side is guaranteed not to move.

Where the clamp meets the plate

Both the standard screw knob and lever releases were tested extensively with plates from 10 different manufacturers, and the lever was found to be much faster in operation, while still feeling just as secure as the screw knob option. On the lever release, the adjustment knob and clamp are fairly difficult to move, so they still provide a solid stop, despite the gap. Particularly nice is the locking button built into the lever arm, preventing an accidental release.

One minor disadvantage to the Acratech lever release is that the large bubble-level ends up hidden beneath the camera when in use, while the screw knob release has this leveling aid riding outboard. However, the lever release has a helpful millimeter scale engraved on the clamps, to gauge any plate offset for better balance or panoramic work, while the screw knob release is curiously blank.

Field experience

The Acratech GP holding up a long lens in the less-than-gimbal position.

Despite the light weight of the Acratech GP, the overall size of the head lends itself to more substantial tripods. This perceived bulk is mainly due to the wide quick release and base compared to the ball, which the GPS and GPSS models mitigate to some degree. However, all of the Acratech heads have a consistent 38mm ball diameter, which is the smallest of any head in this group. This, in turn, comes with a smaller maximum load rating, even though these numbers are not standardized (and tend to be overstated in some cases).

Ball motion

Where the Acratech GP really shines is in the incredibly smooth and consistent ball motion with various amounts of gear and friction applied. Almost any ball will roll around easily when the locking mechanism is disengaged, but the GP joins a select group of heads that deal with increasing loads with aplomb. Most satisfying of all, the ball friction was quite easily controllable through the locking knob and the minimum friction knob, with a large range of adjustment that puts the GP ahead of the other side-clamp ball heads we've tested.

One area that could be improved is the small size and almost smooth knurling of the minimum friction knob. Although this control was quite effective at setting a friction level for various lenses and cameras, it was sometimes hard to turn with bare hands, never mind when gloves were put on. There is also a complete lack of numeric indexing on both the friction and locking knobs, so applying friction for any new lens or camera requires a round of guesswork and knob-twiddling to get things set. Of course, these small issues are no different than the multitude of heads that use a small set-screw embedded in the main knob to control minimum friction.

Gimbal action

 The Acratech GP in gimbal mode, supporting a Sigma 50-500mm lens and a compact DSLR.

A true gimbal head provides a way to balance the size and weight of longer lenses so that they can be maneuvered more efficiently. These specialty heads are even more bulk and weight to bring into the field, so Acratech tries to alleviate that need by adding unique mechanics to their GP and GV2 heads.

What separates the Acratech gimbal function from the drop slot on any other ball head is the unique pin on the bottom of the ball, and the sleeve around the stem. The pin slides into a slot opposite the drop slot, while the sleeve around the ball stem rolls easily within the U-shaped portion of the ball enclosure.

These two elements provide a solid axis for the ball to rotate around while in the drop slot. This also balances the load across the head, instead of simply resting it all in the slot. The side clamp design of the ball lock adds further stability to the gimbal function when under tension.

It was rather surprising how well the Acratech gimbal function worked, considering the problems faced when trying the same balancing act with a traditional ball head's drop slot. The mechanics of this design are well thought out, with the pin and sleeve providing just enough extra stability across the horizontal axis. When testing lenses up to 2kg (4.4 lbs), the head could swing easily in both axes, with the panning base being particularly fluid for tracking. Adding a small amount of friction to the ball allowed for easy starts and stops, even when the length of the lens plate did not allow for a perfectly balanced setup.

Speaking of balance, the main reason that this is more of a gimbal-like function, instead of a true gimbal, is that the lens and camera weight will always be off to the side of the tripod. When using this function with heavier or longer lenses, a substantial tripod is required, along with plenty of weight in a stone bag or hung from the hook beneath the tripod. For truly giant lenses, either a full gimbal head (with the weight balanced over the center of the tripod), or a gimbal attachment like a Wimberley Sidekick is still the best way to go.

An interesting tilt

One rather surprising discovery in the field was a constrained tilt effect that happened after messing with the two ball control knobs. If the minimum friction knob is completely loosened, and only the larger locking knob is used to apply friction, the ball will only rotate along a single axis that is 30° off the drop slot. This seems to be an effect of the shape and pressure of the clamp pads on the ball, and is not mentioned in the manual at all. Additionally, it is very hard to apply enough friction to the ball with the lock knob alone to make this useful for heavier lenses or cameras. Given that Acratech doesn't list this as a 'feature,' it's probably not intended or supported, but interesting in any case.

Stress test results

Sag and lock test

With a 1.9kg, 50-500mm zoom lens mounted using an arca-style lens plate in the Acratech screw-knob quick release, the ball friction was adjusted (using the smaller, dedicated friction knob) to be just enough to hold the lens at a 45-degree angle above the drop slot. Framing the target with this large lens under friction was occasionally jumpy, but still manageable.

Starting point 30 sec. sag result Post-lock result

Once framed, shots taken 30 seconds apart showed almost no droop or creep, with a difference of only 0.15% of the frame. Carefully turning the main knob to fully lock the head down produced a 4.5% shift of the total frame. Oddly enough, this shift was primarily horizontal, unlike the vertical movement seen in conventional heads. Apparently, tightening the off-center lock knob pulls the ball slightly to the side. While the shift direction is unusual, the overall results are fairly average for this group of heads.

Pan lock test

The rubberized panning base knob was unlocked, and then re-locked to "hand tightness." When bracing the tripod, and using a long lens plate as a lever, the panning base did not rotate at all. The Acratech base can be expected to lock and stay put, even when substantial torque is applied.

Cold weather test

When used in the cold of a Canadian winter (sometimes as low as -11° F, -24°C), the ball of the Acratech GP remained quite smooth and easy to manipulate, without any additional roughness. The panning base became a bit slower, but it is fairly fluid to begin with, so this was not a huge concern. Just for kicks, some ice chips and freezer snow was packed around the ball, and sure enough, the open design of the clamp allowed the frozen stuff to melt and fall off the ball and drip harmlessly onto the flat top of the panning base.

The Acratech knobs are almost perfectly suited to being handled with winter gloves on. The thick rubber and generous indentations make turning them quite easy, with only the minimum friction knob being a slippery affair, due to its smaller diameter and smoother surface.

Both types of quick release platforms were also tested. While the screw-knob was just as easy to grip and turn as the other knobs on the head, the lever-lock platform became difficult to unlock due to the very slim profile of the locking button on the lever. Once open, though, the size of the lever was easy to manipulate, so it would still be a good choice for inclement weather.

Summing up

Just the unconventional design of Acratech heads leads to some skepticism among traditionalists, not to mention the unusual claim to combine functions like a ball head, panoramic head, and gimbal head. What the GP delivers, however, is a tremendously smooth and capable ball head that can work reliably as an 'upside-down' leveled panning head for as long as you'd like. Even the gimbal function has just enough extra mechanics to handle mid-sized, collared lenses, when a full gimbal head isn't around.

One downside is the relatively small, 38mm ball at the center of that skeletal frame, which leads to a limited load capacity for a head of this physical size. This last factor is a minor one, given the vagaries of other manufacturers' load claims, and the reality of most photographers' needs. Despite this, the Acratech GP is probably the best mid-sized ball head with the combination of functions that it has, and it rises above most of its competitors.

What we like:

  • Very smooth ball motion at all load levels
  • Equally capable as an upside-down head for level pans
  • Excellent construction, fit and finish
  • Ideal for inclement weather and rough travel

What we don't like:

  • Fairly large and bulky for a 38mm ball
  • GP quick releases could turn in upside-down mode
  • Lack of numeric index for friction levels