Posted on March 31, 2010

 

FLM is a relatively little-known German manufacturer of ballheads. Since they have quite limited distribution (Speed Graphic is the only source of them in the UK) and they don't sell directly online, most of the information available is in the form of photographers asking if they're any good. There are lots of questions, but not many answers, especially when compared to better-known brands.

 

The main attraction to FLM is, of course, the price. Their heads are significantly cheaper than any other reputable brand (Arca Swiss, Acratech, Markins, and so on), generally lighter, and have quite impressive rated capacities. More on that later.

 

I'm in the position of having borrowed an FLM CB38FT for some weeks, and have also recently purchased my own. The executive summary, obviously, is that it is a good head, at least for my equipment, otherwise I wouldn't have bought one. However, "for my equipment" is quite a caveat, since the longest lens I'm using is a 70-200mm f/4, which shouldn't be particularly taxing for any ballhead.

 

It's worth noting that the CB38FT has been redesigned recently, with a concurrent price increase. The new version has the same part number, but has concentric friction and locking controls, instead of two separate knobs. I suspect the internal design has been changed significantly as well. While I think the new version locks down more tightly than the old one, this might just be due to age.

 

Towards the end of this review I discuss what weight capacities actually mean for ballheads, and why the size of the ball is so important. This applies to all heads, and not just FLM.

 

The Basics

 

The CB38FT sits in the middle of FLM's range of ballheads, with a 38mm ball. Below it are the 18, 24 and 32mm versions, and above it are the 48 and 58mm versions. It weighs around 450g, which is considerably lighter than most professional ballheads (although about average for those with 38-40mm balls), and has a rated capacity of 25kg. In terms of specifications, I would consider it to be a small professional head - the three largest sizes have the same features, and differ only in size, weight and capacity. In contrast, the two smallest sizes lack independent friction control, and none of the smaller FLM heads have the tilt control or the PRS option.

 

Cosmetically, the CB38FT is a cylinder of black aluminium, with ridged silver-coloured knobs (except the friction preset ring, which is black). The ball has a metallic finish, and is hollow to reduce the weight of the head. There is a single side channel that allows the head to be tilted up to 90º. A rubber ring around the base of the shaft prevents it from damaging the finish of the top of the head while tilted. The supplied platform is black aluminium with a cork insert, but will almost always be replaced with a quick release clamp anyway. The external finish is all metal, with the possible exception of the friction preset - it's difficult to tell whether it's anodised aluminium or some kind of engineering plastic.

 

The CB38FT has four controls (the CB38FTR adds a fifth, which can also be added to the CB38FT as an optional extra). At the bottom is the pan lock. This was never particularly tight on the version I borrowed, but it seems to be improved on the new one. However, complaints about pan locks are common for most ballheads. There should be no torque on the panning base except while adjusting the head, so it seems unfair to get too picky about it. There is a scale around the base, marked in 10º increments.

 

Just next to the pan lock there is a removable cover for the optional PRS control (this is the only difference between the FT and FTR models). This adds click stops every 15º. The strength of the click stops can be varied, and they can also be disabled completely. The PRS control also allows the panning base to be locked while attaching or removing the head from a tripod, in case you don't have (or don't want to use) set screws.

 

The old style of the head has separate friction and lock controls. This is quite usable, but a bit cluttered, and I found it a little hard to find the correct knob without looking (even though they're different sizes). The new design has a single friction control, with a concentric preset ring to set the minimum friction. This is much the same principle as the Arca Swiss and Markins heads, without the need for thumbnails to adjust the preset. Once the minimum friction is set, the main friction control can be backed off about a quarter turn (without loosening the ball), which locks the preset in place. This prevents accidental changes to the preset friction - to change it, the main friction control must first be tightened further.

 

At the top of the head is the tilt control. This is unique to the larger FLM heads, and locks the ball to one axis. In effect, it becomes a 2-axis pan and tilt head. It's not really true to say that it locks the ball - rather, it increases friction dramatically in all but one axis. In practice, the ball will still move in other directions with a bit of force. I'm not convinced the tilt control is particularly useful, although it might be worthwhile for video use. However, the models without the tilt control can't be upgraded with the PRS control, so it's worth getting the tilt option anyway.

 

Tripod and Camera Attachment

 

The CB38FT has a standard 3/8" thread for attaching to a tripod, and a removable stud screw with both 1/4" and 3/8" threads. It comes with a simple circular platform with a cork insert, which should normally be removed for attaching a quick release clamp. The head relies entirely on friction (and optional glue) to stop the clamp from twisting - this means it should be compatible with any standard clamp, including the Wimberley ones. FLM recommend using a thread locking compound to keep the clamp in place.

 

FLM make four quick release clamps, but I haven't used any. Two are Arca Swiss compatible clamps in different sizes, both with lever releases and built in spirit levels. The other two are a proprietary design that uses a very small camera plate. It's unusual in that most of its strength comes from the clamp pressing against the base of the camera, rather than how tightly the plate is attached. However, I can't comment on how it actually performs in reality. FLM also make a separate levelling base.

 

The Great Weight Capacity Swindle

 

This section is fairly technical, and is more of a general rant about ballhead weight capacities. Most of the technical details here should be taken with a fairly substantial grain of salt - I'm not a physicist, and am liable to be wrong, however logical the arguments seem. In any case, I should be a bit closer to the truth than "OMG this head is fantastic it can hold 25kg!!!1!". Rest assured that the CB38FT is more than strong enough to hold 2-3kg of equipment off-centre, and actually quite a lot more. The question is what the real maximum capacity is, because depending on how FLM measure it, the head could hold anywhere from 5kg to 25kg in a real-world setting (and even more if it's upright and well balanced). Regardless of this, any 38-40mm head should hold any lens you'd actually be willing to carry any distance, and the FLM is no exception. For huge lenses you need a much larger ballhead, or ideally a gimbal head.

 

Generally, ballheads are made of fairly solid metal, and I would expect them to hold at least 100kg before suffering any damage, and probably a lot more. If your load is properly balanced and centred, any good quality ballhead will support it easily. The reason rated capacities are much lower is that this simply isn't interesting: what we're interested in is how much the head can support off-centre.

 

Now, the reason I'm rambling about this is that until you hit the point where it can actually be damaged, no head actually has a fixed weight capacity at all. Rather, it is capable of resisting a certain amount of torque. Torque is (roughly) a measure of how much the ball is being twisted, and is given by the product of force and distance, with the force in a direction perpendicular to a line between the centre of the ball and the centre of the load. The SI unit of torque is the Newton-metre (Nm). If you have a 2kg camera, with its centre of gravity 10cm from the centre of the ball of your head, then the maximum off-centre torque is about 1.96Nm. If the camera is upright and perfectly balanced, then there's no torque because all the force is towards the centre of the ball. If you had a 1kg camera with its centre 20cm from the ball, it would have exactly the same maximum torque, and the ballhead would have just as much trouble supporting it off-centre. In general, if the camera is more-or-less balanced, the distance is probably around 9-12cm. I'm assuming 10cm for the rest of this article, because it makes the calculations easier. If you're using a heavy lens with no tripod collar, or have an unusually tall foot on the collar, then the distance might be rather greater. It'll also be a bit larger for bigger ballheads, simply because of the larger ball.

 

Anyway, all this means that the load a ballhead can support depends very much on how far away it is, and that means that the rated capacity of a ballhead means precisely bugger all, unless we know the distance at which that weight was applied when it was tested. FLM's marketing blurb seems to suggest that they test by applying lateral force to the top of the shaft on the ball - for the CB38FT, that's about 2.5cm from its centre. This means that in a real-world environment, the head will probably only support about a fifth to a quarter of its rated weight. Maybe more, because it's just marketing blurb and we don't actually know how it was tested. Even so, that's over 5kg for the CB38FT, which is quite a lot of equipment, and more than you'd want to put on a typical lightweight tripod. Please note that I'm not suggesting this is a further multiplier in addition to the normal recommendation to get a head that can hold several times the weight of your equipment - rather, I'm trying to explain why this is good advice.

 

To the best of my knowledge, the only manufacturer to give torque ratings for their heads is Markins, although they use rather unusual units (to convert from kgf-cm to Nm, divide by about 10.2). It's obvious from their specifications that their weight capacity is for a load 5cm from the centre of the ball, so the real weight limit is probably about a third to half what they claim. It also seems that there's something a bit fishy about their torque ratings - if we were to take them at face value, then the Q3 would be able to hold considerably more than any other 40mm ballhead, including the Kirk and Really Right Stuff models.

 

Finding a 25kg load is not easy, but I do happen to have a lighting stand that allows me to apply a lot of torque without very much weight (about 1.2kg). I screwed the stand into the top of the CB38FT and extended it until the head could only just support it at (almost) 90º to the tripod. That put the centre of gravity of the stand about 75cm from the centre of the ball, which gives a torque of about 8.82Nm. That means the head should support about 9kg at 10cm, and maybe more if you can tighten it further without hurting your hands. It will hold that load still, at the worst possible angle, with no creep (although you won't have to push it very hard to get it to move, and you probably can't lock it down much further). Of course, it will also be able to hold a larger load at less extreme angles. If, as their marketing blurb seems to suggest, FLM test their heads by applying force directly to the top of the shaft on the ball, 9kg actually overloads the head by about 50%. Particularly sharp-eyed readers might notice that mine is on a Manfrotto 190 series tripod, and so anything over 4.5kg is going to exceed the tripod's maximum capacity anyway.

 

Incidentally, users of the Wimberley Sidekick and similar devices are not restricted by this limit. Since the Sidekick and lens should be properly centred, there should be no torque on either the head or the Sidekick, and it should hold pretty much anything.

 

So, in summary: the off-centre capacity of the CB38FT is somewhere around 7-8kg for actual use (I'm not about to claim that you can actually get 9kg onto it consistently and reliably). Looking at the specifications for some similar size heads, we see that the ratings for equivalent Kirk and Really Right Stuff heads (7kg and 8kg respectively) are probably accurate. On paper, the Markins Q3 should get about half its rated capacity, but that's still twice the load of any similarly sized head. I don't really believe that, but it's possible that their "fluid style main tension knob" allows the Q3 to apply more pressure to the braking pad than other heads.

 

Possible marketing shenanigans aside, let's see torque ratings from more manufacturers, please.

 

Why Size Matters

 

Most experienced photographers already know that the size of a ballhead makes a big difference to its weight capacity, but it's quite surprising just how much difference it can make. Going from a 40mm to a 60mm ball gives at least three times the weight capacity, and arguably up to five times.

 

A ballhead works by pressing a braking pad against the ball. The torque a ballhead can resist is given by the amount of force the pad can resist, multiplied by its distance from the centre of the ball - which is exactly the radius of the ball. This means that torque (and therefore weight capacity) is proportional to ball size, and we can increase capacity just by making the ball bigger and leaving everything else the same.

 

Of course, we don't really expect manufacturers to leave everything else the same. A bigger ball means more space below it, and this usually means a bigger braking pad. The force the pad can resist is proportional to its area, which is proportional to the square of its radius, which is almost certainly proportional to the size of the ball. So we find that the torque is proportional to the cube of the ball size. Therefore, going from a 40mm to a 60mm ball (a 50% increase) multiplies the weight capacity by 3.375. Unfortunately, if we just scale everything up it has the same effect on the weight of the head. However, we don't actually have to make the walls of the head (or the ball, if it's hollow) thicker, so it should be possible to keep the weight proportional to the ball size squared. So we should be able to get 3.375 times the capacity, with about 2.25 times the weight - and if we have a look at the weights and capacities of some professional ballheads, that's about what we see.

 

There is one more thing that can increase weight capacity. The force the pad resists is also proportional to the force it applies to the ball, although maybe not directly, and this is proportional to the torque the user can apply to the friction control. If the friction control is larger, then we can comfortably apply more torque, and get a greater weight capacity - provided the mechanical parts of the head can actually handle that much force (and since they're bigger, they probably can). Once again, the size of the main control knob tends to be proportional to the size of the ball. This gets us up to five times the capacity, just by scaling everything up by 50%.

 

The conventional design for ballheads has a pad that presses against the ball from below. The FLM heads certainly follow this pattern, and it looks as though the Kirk and Markins heads do the same. A few other heads, including Really Right Stuff, Acratech and Burzynski, use a design where the ball is clamped around its circumference. This gives an enormous contact area, which should result in a huge weight capacity. Looking at their overall design, the rated capacity of the RRS heads seems remarkably low.

 

Conclusions

 

The CB38FT is not a ballhead for heavy telephoto lenses, although it could probably hold most of them without too much trouble. If you want a head to support a 5kg lens, there are better choices - and if you do have one of those lenses, you shouldn't need me to tell you that a 38mm ballhead isn't big enough.

 

This is a ballhead for use on a tripod that you're actually going to carry for an appreciable distance. It's reasonably lightweight, and is strong enough to hold an SLR with all but the longest and fastest telephoto lenses. Oh, and it's a good deal cheaper than the Markins Q3 and RRS BH-40, both of which are lighter. The rated weight capacity is overinflated, but it will hold 7-8kg at any angle, if it's reasonably well balanced on a tripod collar with a sufficiently low-profile foot. It'll certainly support anything a lightweight carbon fibre tripod will.

 

For more reasonable loads, the friction control is more than adequate to find the "sweet spot" which seems to characterise professional ballheads, and the newer design friction preset makes it impossible to loosen the head so far that there's a risk of damage to the camera. The tilt control is interesting, and might be useful for video or large stitched images, but is hardly essential. The same can be said for the optional PRS control.

 

I'm unwilling to make an outright recommendation to buy this head since I haven't handled anything else of a similar size (except the Giottos models, which I was not impressed by). However, the FLM head performs very well with my equipment, so I'm unlikely to do so any time soon. Make of that what you will.

© 2002-2016 James Matthews. All rights reserved.

 
 
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