Tripod stability: a few thoughts and some primitive experiments. (1 Viewer)

I'll start off with a few controversial assertions and am open to contradiction:

1) There are no substitutes for leg diameter and weight.

2) The fewer the number of leg sections, the better.

3) Soft surfaces damp better than hard.

4) For a given tripod height it really doesn't matter if you achieve that with the legs or the centre column.

5) Hanging weights from the centre column is contraproductive.

6) There should be metal to metal contact between head and scope, i.e. minimal compliance.

For the tests I set up my Swarovski 65 mm scope on two different tripods, rapped a tripod leg with my index finger and timed the vibrations until they were no longer visible at 30x magnification. The impulse, of course, was variable but I was nevertheless able to achieve fairly reproducible times.

The tripods used were an old Gitzo Series 4 and a basalt Gitzo GT2942L. The Series 4 has three 1,6 mm thick aluminium leg sections of 37, 32 and 28 mm diameter and weighs nearly 4 kg. Gitzo now use a stronger aluminium alloy of only 1,2 mm thickness, which for the same diameter would probably be just as resistant to denting and lighter too, but the elastic modulus doesn't change with the alloy composition, so the old thicker tubes would be 1/3 stiffer.

The basalt tripod has four leg sections of 28, 24, 20 and 16mm diameter and goes up to 151 cm without extending the centre column (161 cm for the Series 4). The stiffness of tubes of the same material is proportional to the material thicknes and to the cube of their diameter, so the top sections of the basalt tripod are over five times as stiff as the bottom sections! Hence the recommendation to keep the number of leg sections to a minimum compatible with height and packing requirements.

Heads used were a Berlebach 552 pan and tilt on the basalt and a Gitzo 1277 ballhead with Novoflex Q-Mount on the Series 4, both Arca Swiss compatible. They are both more than adequate for the little Swaro.

Using just the three top leg sections of the basalt for a height of 120 cm w/o head, vibrations subsided after 3 sec on a heavy woollen carpet and 5 sec on solid wooden flooring. I assumme that vibrations are reflected back into the tripod from the hard surface. Using the top two sections of the Series 4 for a height of 114 cm, the tripod returned instantly to its original position with a half cycle of movement. On the hard surface it was about one full cycle.

With all leg sections extended on the basalt tripod (I had to rotate the angled scope in its collar) it vibrated for 5 sec on carpet and 10-12 sec on the hard surface. In the latter situation the amplitude subsided and then increased again several times due to the interaction of the different tube sections. Hanging 3 kg from the centre column reduced the high frequency vibration time to 5 sec but any pendulum movement of the weight (and this is going to happen in the wind) induced a corresponding low frequency movement of the whole tripod.

Lastly I fully extended the centre column of the basalt tripod but only the top two leg sections, also for a height of 120 cm. Of course the footprint is smaller so the trripod could be more easily knocked over. The vibration time on the hard surface was 5 sec, the same as with three leg sections and collapsed centre column. The centre columns on most tripods are of similar diameter to the top leg sections, so what one loses here is probably compensated by the losses of the thin leg sections.

John

Very interesting, John. I'd agree with all the above, except no. 4). I usually prefer to gain height by extending the legs, keeping the central column as short as possible. I think my central column is more inclined to waver in high winds, and also by keeping it short, and extending the legs fully, I get more leg diameter, i.e. a wider and more stable base. Don't know if this makes sense.

Sancho said:

Very interesting, John. I'd agree with all the above, except no. 4). I usually prefer to gain height by extending the legs, keeping the central column as short as possible. I think my central column is more inclined to waver in high winds, and also by keeping it short, and extending the legs fully, I get more leg diameter, i.e. a wider and more stable base. Don't know if this makes sense.

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Yes, Sancho, I agree on the base or footprint issue but thought that the extended centre column "Verbot" was one of the established "truths" that should be questioned. As a cyclist, you are no doubt aware of the old myth of narrower tyres having lower rolling resistance.

I think it all depends on the relationship of centre column diameter to smallest used leg section diameter, and can well imagine that a stable wooden Berlebach would be compromised by extending its 25 mm dia. aluminium centre column.

Why not try it out yourself on a hard surface? You only need a tape measure and a stopwatch.

I repeated the experiment today at 151 cm tripod height with the basalt tripod. With 28 mm centre column extended and 20 mm bottom leg sections, vibrations ceased after 9-10 sec and with collapsed centre column and 16 mm bottom leg sections they lasted 10-12 sec.

I was so impressed with the stability of my 30 year-old Gitzo scaffolding that I think I will buy it a Manfrotto 128LP and use the Novoflex Q-Mount for Arca Swiss compatibility. For the rare birding situations where I don't have to carry it far, or for viewing the moon and planets it should provide a very solid base.

John

John Russell said:

(...)
4) For a given tripod height it really doesn't matter if you achieve that with the legs or the centre column.
5) Hanging weights from the centre column is contraproductive. (...)

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Hi John,

in principle I agree with you but I would like to add two things:

4) In the case of a common consumer tripod (Manfrotto 055 or worse) it actually does matter because the fixing mechanism of the tripod shoulder / center column regularly is way too flimsy. Hence, not the diameter of legs or columns poses a problem but the wobble in the clamping which is the more magnified the higher you extend your center column - even if its tube is perfectly rigid.

5) I agree but like to amend that the absorbability of any tripod increases considerably if a weight (e.g. a photo bag or a backpack) is imposed with its shoulder strap *over* the three tripod legs (and *not* dangled on a hook *under* the head). By this, the legs are joined together, pre-tensioned and extra damped. This is an old trick that I learned from a Leica instructor years ago. Just try it!

John Russell said:

1) There are no substitutes for leg diameter and weight.
2) The fewer the number of leg sections, the better.
3) Soft surfaces damp better than hard.
4) For a given tripod height it really doesn't matter if you achieve that with the legs or the centre column.
5) Hanging weights from the centre column is contraproductive.
6) There should be metal to metal contact between head and scope, i.e. minimal compliance.

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1. Agreed when all else is kept equal. If not, then there are substitutes, for example build quality and the type of material used. A light weight well-constructed carbon fiber tripod can easily out perform a heavy but poorly engineered aluminum tripod.

2. Agreed if it means more wonky connections and spindly lower leg sections. Construction quality and engineering matter a lot here.

3. Depends on the situation.

4. I disagree. Far better to extend legs. Most noticeable to me in practice is that center columns don't resist twisting motions around their axis.

5. Mostly disagree, but depends on the situation. Most of the time, I think weight is helpful, especially if one is using an otherwise solid tripod with a load well under its limit.

6. Agree.

--AP

forent said:

I agree but like to amend that the absorbability of any tripod increases considerably if a weight (e.g. a photo bag or a backpack) is imposed with its shoulder strap *over* the three tripod legs (and *not* dangled on a hook *under* the head). By this, the legs are joined together, pre-tensioned and extra damped. This is an old trick that I learned from a Leica instructor years ago. Just try it!

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Forent,

That's amazing!

In the worst case situation with all four leg sections of the basalt tripod extended, it took a mere 3 sec for the vibrations to be damped out by hanging a binocular bag (including field guide) over the legs. Without, it took 10-12 sec.

The only proviso is to keep the bag near one of the tripod legs to avoid any pendulum movements.

Many thanks for this. It is something every scope user should know.

John

John Russell said:

by hanging a binocular bag (including field guide) over the legs.

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Guess I wasn't reading carefully enough, because that's the way I hang weight from a tripod too, and what I had in mind when I gave my opinion earlier on assertion #5.

--AP

John Russell said:

(...) That's amazing! (...)

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Glad to be of help! :t:

I've always just suspended my backpack from the hook on the bottom of the center column but I wonder if putting it in a stone bag, which is normally connected to and suspended under the legs, will yield a better result?

RJM said:

I've always just suspended my backpack from the hook on the bottom of the center column but I wonder if putting it in a stone bag, which is normally connected to and suspended under the legs, will yield a better result?

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Rick,

I think the solution with the backpack attached to the centre column would only be effective if the backpack had minimal ground contact to prevent it from swinging. It makes me wonder if the tripod manufacturers are just blindly following convention by putting a hook on the centre column, and if they have ever tried looking through a scope with a weight swinging underneath it.

Although there are no fundamental differences in the requirements of scope users and photographers, it seems paradoxical that scope users experience tripod deficiencies in real time, yet photographers are more wiiling to spend a lot of money on supports. I recently saw a documentary on Heligoland in which some bird photographers were using tripod/head combinations in the €2000 category.

In any event, you should try forent's solution from post #4. It's very effective.

John

forent said:

5) I agree but like to amend that the absorbability of any tripod increases considerably if a weight (e.g. a photo bag or a backpack) is imposed with its shoulder strap *over* the three tripod legs (and *not* dangled on a hook *under* the head). By this, the legs are joined together, pre-tensioned and extra damped. This is an old trick that I learned from a Leica instructor years ago. Just try it!

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Can anyone please post an image of this type of setup as for some reason I cannot visualise it. I don't know if I am being silly but I don't get how to do it and would like to try it.

Stritchy, here are two quick&dirty pictures, one with the backpack dangling from the hook under the head (with the red "Don't!" cross ) and a second where the backpack is attached in the way I recommend. (Of course you can alter the position and kind of bag / weight to your tastes.) Hope this helps!

forent said:

Stritchy, here are two quick&dirty pictures, one with the backpack dangling from the hook under the head (with the red "Don't!" cross ) and a second where the backpack is attached in the way I recommend. (Of course you can alter the position and kind of bag / weight to your tastes.) Hope this helps!

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Thanks forent. I get it now. That looks like a really good idea. I will definitely try that out when I next use my tripod.

RJM said:

I've always just suspended my backpack from the hook on the bottom of the center column but I wonder if putting it in a stone bag, which is normally connected to and suspended under the legs, will yield a better result?

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I suppose the stone bag would work better than the hook solution as it connects all three legs but it's not my cup of tea because I try to avoid any superflous item when I'm out in the field where a bag or backpack is always with me anyway and does the trick.

John Russell said:

Why not try it out yourself on a hard surface? You only need a tape measure and a stopwatch.

John

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I had some down-time today, John, and I tried it. You're right. I don't know why you're right, because I didn't pay attention in maths class in the 1970's. It's kind of counter-intuitive, but a raised centre-column seems more stable than raised legs. This one I'll leave to the boffins!

two-section legs

As for two-section legs.... I didn't believe the benefits until I started using a Davis & Sanford Magnum tripod (2-section legs) with a Manfrotto 128RC.

Aside from stability, setup time is very quick.

Jerry at the Audubon Shop in Madison, Connecticut offers the combo as "The Birder Tripod."

Check it out at http://www.theaudubonshop.com/