An occasional consideration for the landscape photographer is the likelihood of their tripod blowing over in the wind. This has so far only happened to me once, but I have heard of this issue many times before.
The likelihood of a tripod tipping over is related to the strength of the wind and the cameras centre of gravity relative to the location of its feet. A tripod with a wide base is hence less likely to tip over in the wind. The size of the tripod base is one of the most significant factors when it comes to resisting tripod vibration in the wind. A wide base is highly desirable in this regard. The trade must be made by the tripod manufacturer as to whether to prioritise maximum height or the size of the base. Setting a wider leg angle increase the size of the base and stability but also reduces its height.
I recently purchased a Gitzo 1541 Mountaineer. The tripod wasn’t for me for a number of reasons but the biggest issue I had was the relatively narrow base at the tripods highest setting. I felt that the ‘default’ leg angle was simply too acute and stability had been sacrificed to squeeze out a tiny bit of additional height. I have since reverted back to my G2228 Explorer tripod, to allow me to set the legs as wide as I like. However I thought I would look into leg angles to see if Gitzo, Manfrotto and other tripod manufacturers were getting it right or not.
The diagram below shows the simple trigonometry and algebra to see the trade-off between height and stability. The diagram considers the worst tripod orientation relative to the wind direction (not that this matters when it comes to the analysis)
Where D is the drag force due to wind W is the combined weight of the camera and tripod (a constant) A is the leg angle At the tipping point drag force D is proportional to TanA.
H = LCosA
Where H is the tripod height with centre column retracted L is the length of the tripod leg (a constant) A is the leg angle The height H is proportional to CosA
Now if we plug in some values for A (in this case 24 degrees, 30 degrees and 35 degrees) then we can see how a wider leg angle might affect tripod height and tripod stability.
- Tan24 = 0.445
- Cos24 = 0.913
- Tan30 = 0.577
- Cos30 = 0.866
- Cos35 = 0.819
- Tan35 = 0.700
If the standard leg angle was changed from 24 degrees to 30 degrees this would result in a resistance to tipping increase of 30% with a reduction in height of only 5% (without the centre column) this would mean that the Gitzo mountaineer would go from 138cm to 131cm for a 30% increase in tipping resistance. Setting the leg angle to 35 degrees reduces the height by 10% but increases tipping resistance by a massive 57%!
The trade between height and stability/tipping resistance is a hard one to strike. In my opinion the standard leg angle of 24 degrees is too narrow. A leg angle of 30 degrees would produce a marked stability increase at a minimal cost to extended height. The issue is compounded further if you don’t set up the tripod properly. Setting it up at an angle pointing downwind increases the tripods likelihood of tipping over and reduces its stability. This is the regular cause of tripods blowing over in the wind. A wider tripod base would allow a greater margin for error. This all leads me to the conclusion that having variable leg angles is a hugely useful feature. When its really windy you can set your tripod legs to 35 degrees, increasing stability by 57% with only a small reduction in height. Equally when it is calm you might like to set the legs to 20 degrees to gain a higher viewpoint.