Sirui K-40x
$200 / £120  www.sirui-photo.com

The Sirui K-40x

Sirui is a relative newcomer to the North American photographic support market, but after a decade of experience in China, this manufacturer is building a reputation for quality at much lower prices than their main competitors. The full Sirui product catalog includes a variety of tripod heads, including video and full gimbal heads, along with a wide range of tripods and monopods.

The K-40x is the largest Sirui ball head in the company's "professional" KX series, and competes quite well in specifications with the other heads in this review group, but at the lowest price point. The question is whether it performs as well as these specs suggest.

Specifications

Ball diameter  54mm (2.1")
Height  125mm (4.9")
Weight   700g (1.54 lb)
Base diameter   69mm (2.7")
Maximum load  35kg (77 lb)
MSRP   $200
Warranty  6 years

Design and features

Rather than the usual "beer can" cylinder profile of most large ball heads, the Sirui K-40x has a flared profile that's more like a thermal mug, but a mug carved from a block of aluminum. After this initial flourish, most of the controls and details are similar to many other heads on the market. The sky-blue accents on the knobs and friction index ring keep the the head from being monochromatic, and the slight scalloping of the case is echoed in the grip carved into the base. The entire Sirui KX line of ball heads share this same shape, finish and detailing, even as they get progressively smaller.

The K-40x comes nicely packaged with a neoprene bag that doubles as a travel cover, a 70mm Arca-style camera plate for the quick release, and a surprisingly well-written and illustrated instruction sheet. Also in the box is their 6-year Warranty card, and a small quality control chit that came in handy during the course of the review (more on that later).

54mm Ball

With a glossy coated, 54mm ball, the K-40x shares a critical dimension with many other heavy duty ball heads. This ball diameter promises a greater load capacity and smoother rotation than smaller Sirui KX  heads, along with greater locking power due to the increased surface area for the locking mechanism to grasp.

This also makes the specifications of this Sirui head almost identical to many competing brands, which may have been the greater point.

Quick Release Platform

Most professionals and serious enthusiasts use Arca-Swiss-compatible camera and lens plates to quickly switch equipment on their heads. Sirui recognizes this and uses this standard for all of its ball heads.

The quick release included with the K-40x is a simple screw clamp type with three (legible) bubble levels for leveling in each axis, and a retractable safety stop pin that matches the safety recess of the included 70mm camera plate.

Friction and Locking Knob

Like many other ball heads, the Sirui heads in this series all use a large, single knob for controlling the friction and locking of the ball, along with the familiar "screw dial" in the face of the knob to set the minimum friction amount.

The Sirui KX-series heads also feature a "friction index ring" at the base of the main knob, to indicate how much friction is currently applied. However, this is a user-calibrated feature that does not directly set the friction.

Construction and handling

With a solid heft and a fine, consistent finish to all the aluminum components, the Sirui K-40x is rather impressive when held in the hand. The flared body, thick walls, and wide base all add to this substantial look and feel, but this is not a particularly heavy head for its overall size and ball diameter.

The K-40x is almost entirely made from machined aluminum (as casting cannot produce the fine edges and indents in the body), from the base to the simple quick release. All of the knobs are solidly made of metal as well, with rubber grip rings on them. The fit and finish was pretty good overall, but the bubble levels in the front of the quick release were installed at a slight angle, and the rubber ring around the main knob was not a perfect fit, and can be seen slightly deformed in the photos.

The supplied quick release plate is also machined from aluminum, with a very wide platform and plenty of weight-saving channels cut into the underside. Unfortunately, its width meant the Sirui plate covered the round bubble-level on the quick release platform when clamped on the head. It is an otherwise very nice, universal plate for many cameras or larger lenses, and Sirui recognizes that their consumers might not have an Arca-compatible plate before buying this head.

Ergonomics

The size and grip of the knobs is basically industry standard, which is a good thing, and the feel and feedback in the knobs is particularly satisfying. The main ball locking knob has a slightly firm resistance that allows finer control over the progressive friction, and the index ring remains aligned with the knob to assist with repeating friction settings. The pan lock knob is all metal, with a slightly slippery grip due to very subtle knurling on the surface, but it has a short throw for locking the base down. All knobs are also captive, meaning they cannot be completely unscrewed off the head.

Sirui KX-series ball heads all share a simple, and fairly conventional, control layout that makes their use easy and consistent. When using the drop slot for portrait orientation (with the camera tilted to the left), the main lock knob is conveniently pointed back at the photographer. The pan lock knob ends up on the right side, requiring a bit of a reach, but the important control is still right at hand. For an increased range of tilt downward, grasping the main ball lock and pan lock knobs remains easy, but when tilting upward (with the drop slot facing back) the controls end up on the front and right. Overall, this arrangement is the one that works for many other heads and many photographers, so it will be fine in most situations as well.

Multi-function knob

Following the lead of many other ball head innovations, Sirui integrates the minimum friction control into the main ball friction and locking knob with a small dial (or thumb-screw). While it's a small feature, the raised edges and channels make it easy to turn with a fingertip, and it appreciably changes the minimum friction possible with the main knob by restricting how far the knob will turn to unlock the ball. This little functional detail is not always well done on the other ball heads with the common control, so Sirui is to be congratulated for doing it well.

The main friction knob is firm and provides increasing resistance as the friction level increases, making adjustments fairly intuitive. Completely locking the ball requires a good bit more turning power, but there is some satisfaction in knowing the ball won't be moving.

Panning base

The small, but legible, panning base indicator of the K-40x.

With only a little window in the base to show the indexed degrees, the K-40x still tries to make precise panning easy with this large head. The index numbers go from 0 to 90, and back down to 0, in 15° increments, while there are lines every 5°. These markings are quite bright and legible, and the window has a white index arrow that is very easy to read. Too many other ball heads lack even this basic legibility, and with a very slow (but smooth) panning action, the Sirui K-40x is ideal for precision pans.

The quality control story

As sometimes happens with any manufactured item, the first K-40x head we received was not up to Sirui's (or anyone's) quality standard. The head appeared new, but the Quality Control chit was dated early 2011. Normally, this isn't something to even bother looking at, but this initial head had a few problems. Out of the box, the initial sample head had a very sticky ball motion at all friction levels, and the the main locking knob wobbled in its case.

After contacting Sirui support (in China) as a regular consumer, there were many quick and helpful replies, and an exchange was arranged, with free shipping for the return. The replacement head showed none of the stickiness or locking knob problems, and had a Quality Control chit from 2013. All of the testing and review work was done with this second unit.

No inferences or generalizations about Sirui should be made from this, as two other products in this ball head review group also had to be exchanged due to problems. The reason for mentioning this (for any product) is to underscore the importance of the warranty, serviceability, and manufacturer's customer support. Sirui did not disappoint here at all, and is gaining distributors in various countries to handle this kind of issue locally.

Field experience

In the field, the K-40x mates well to a larger tripod, although the height and weight added to the top is substantial. The rounded base profile, with cusps cut out for gripping it, was actually quite welcome when attaching or detaching the head from the Gitzo Safe-lock platform. The similar cuts into the sides of the flared body served no purpose other than to add some visual appeal.

Ball motion

What this head adds to any tripod is a very smooth and controllable ball motion, with a feel that is almost luxurious when compared to the other heads in this review group. In fact, the Sirui comes in a close second (to a head that sells for three times as much) for the ease of maneuvering the ball while under friction. This excellent motion remains even when heavier loads are put on the head, with the only difference being a slightly stiffer locking knob.

Quietly productive

Perhaps most surprising of the field experiences with the Sirui head was just how little there was to complain about. The basic functions are well handled, and once familiar with the control layout, the K-40x just quietly does its job. If there is a nit-picking detail to be mentioned, then the lack of safety stop channels in the quick release platform is one. This makes the common screw heads at the ends of many lens plates, and some camera plates, just something that gets in the way. Not every plate has a recess in the right place for Sirui's own safety button to work with them, but it's thankfully spring-loaded and will retract when a flat plate is put on the platform.

Panning with a Sidekick

The panning base, as mentioned earlier, is a little stiff and slow to turn, which makes precise pans easier at the expense of quick rotations. There is a trend for panning bases to use thicker grease to provide this damping effect, which is a bit defeating when the ball on top can move almost as slowly and precisely, but the ball does not restrict the rotation to a single axis.

The K-40x holds a Wimberley Sidekick confidently, but pans are too slow to replace a true gimbal head.

All of the ball heads in this group were field tested with a 500mm lens and a Wimberley Sidekick gimbal-style attachment. This device uses the drop slot and panning base of large ball heads to hold long lenses, and permit moving them in a very controllable way. When using a Sidekick on the K-40x, the slow pan base made tracking subjects particularly difficult, and a true gimbal head would be a much better choice for long lenses. That said, there was little issue with using the panning base when not tracking subjects, or with shorter lenses.

Stress test results

Sag and lock test

With a 3.1kg, 500mm lens mounted with an Arca-compatible lens plate on the K-40x quick release, the friction was adjusted to hold the lens at a 45-degree angle without slipping in the drop slot. Framing the target with this large lens was still quite easy thanks to the Sirui's smooth ball motion and very fine friction control.

Starting point 30 sec. sag result Post-lock result

The K-40x showed very little sag in between shots taken 30 seconds apart, with an average change of just 0.24% of the frame. When the friction knob was carefully turned to lock the ball, there was a fairly significant shift of 4.1% of the total frame, which is on the mid- to low-end of the test group. This says the head can still handle large loads, but critical framing may not always be preserved.

Pan lock test

The panning base knob was unlocked, then re-locked to hand tightness to test the veracity of the pan lock. The tripod was braced, and using a long lens plate as a lever, the panning base showed no movement at all, and actually seemed to get tighter as more torque was applied. This was evident after the test, when unlocking the pan knob took quite a bit more strength to turn the knob than the locking action did. After this test, the knob remained easy to lock and unlock in normal use.

Cold weather* test

*It should be noted that although the head was tested in Canada, it was during the summer. To compensate for this, the head was placed in a sealed bag with a desiccant for 2 weeks, then put in an industrial freezer at 14 F (-10° C) for 8 hours. The head was re-evaluated for ball and pan motion while cold, and for control use with heavy winter gloves on.

During the "freezer test" (to simulate wintry temperature conditions), the ball of the K-40x felt a bit stiffer, as if extra friction was applied, but it was still smooth. The panning base showed no appreciable change in either smoothness or stiffness, although it was pretty stiff to begin with.

Working the Sirui K-40x with thick, winter gloves on was sometimes a trial. The main locking knob and the quick release knob were easy enough to grab and turn, but required more concentration and pinching force. The pan base knob, which is already small and a bit slippery to turn bare-handed, was basically ornamental until the gloves came off. Without the protection of the gloves, the body-heat transfer to the very cold metal knob was instant and biting. For lots of serious, cold-weather work, a rubber cap for the pan knob, or maybe a separate panning base might be in order.

Summing up

Sirui has managed to create a very fine ball head at the top of their KX line, and one quite worthy of the professional designation. It should not be surprising that the largest and best ball head from a manufacturer is very smooth, stable, and easily handles large loads, but testing the K-40x shows that Sirui did not cut many (if any) corners to get the price of this head down. it's this low cost, high performance combination that may be the single most distinguishing feature in a head that otherwise ticks all the usual boxes, and does not stray too far from the ball head status quo established by other brands.

While we did not subtract rating stars from other heads for being particularly expensive, the whole Sirui K-40x package is such a remarkable value proposition in comparison, that a half star was added. While there are a few very minor negatives, this bump up negates them, resulting in a five-star product rating.

What we like:

  • Smooth ball rotation under tension
  • Simple, durable design
  • Confident ball locking action
  • Low price but high value

What we didn't like:

  • Stiff panning base
  • Included QR plate covers the top bubble level
  • Minor fit and finish issues (angled bubble levels, rubber grip)

To read the next ball head review, use the arrows or table of contents below. On the last page, we recommend three that stand out from the rest of the field.