[Brightcolours]

The force (torque) pulls the element down, you hold the camera, don't you? That is the "rotation point". The further the weight is from where you hold the camera, the higher the torque. The weight remains the same, of course.

[davidmanze]

The force (torque) pulls the element down, you hold the camera, don't you? That is the "rotation point". The further the weight is from where you hold the camera, the higher the torque. The weight remains the same, of course.

     

 I understand what you are saying BC but no! ...... you are talking about a "bending moment" .... which means a deviation from a straight line ...... leaf spring suspension is a form of bending moment   .....  

 .....    "torsion bar suspension" is a elastic/ spring force brought about by twisting/rotation of one end only of a round spring steel suspension bar for example ..... 

 you must differentiate between "a twisting force" and a "bending force"

 ......... a "crow bar" exerts a bending force (linear straight line force).......

 ........ a spanner imparts torsional force on a nut (rotational force ...... about the bar's own axis ) .....
  
  No matter how or where you hold the camera/ lens, you are only supporting the weight of the combination (linear force oriented by gravity) ...... you are never applying a twisting moment about the lens's own axis ....

[Brightcolours]

You hold the camera, the nut in your example. The lens weight -> spanner. If the lens is too heavy you dont drop the camera, rather the lens will rotate downward.

[davidmanze]

You hold the camera, the nut in your example. The lens weight -> spanner. If the lens is too heavy you don't drop the camera, rather the lens will rotate downward.

 No  ...... This is basic physics terminology BC .... I was taught at school in physics to always use the correct terms to avoid ambiguity ...... 

 ...... a lens rotating downward ?? ...... you know in all my years of reading about photography this is a first for me!! ........ 

  ....... even "after" a heavy session at the pub ......   .......  "when having had the occasion of making love to a nice young lady ....... I've never said .. "sorry darling I can't tonight, I've drunk too much .........   my penis is rotating downwards"    

 I note in my latter years it sometimes does ...  but I've never before phrased it in that fashion ......

[Brightcolours]

Yes, it does. I can't use "correct terminology" because my physics courses were not taught in English (and were long ago, of course).

You hold the camera, yes? That is the point of rotation. The further away you move the weight from that point, the harder it is to keep the camera pointing horizontal, the more force you have to apply to counter that the lens is going to point downward (the rotation I mentioned). You have to "counter" the rotation with your hands, with your muscles.

[davidmanze]

Yes, it does. I can't use "correct terminology" because my physics courses were not taught in English (and were long ago, of course).

You hold the camera, yes? That is the point of rotation. The further away you move the weight from that point, the harder it is to keep the camera pointing horizontal, the more force you have to apply to counter that the lens is going to point downward (the rotation I mentioned). You have to "counter" the rotation with your hands, with your muscles.

I understand you didn't study English physics definitions in your youth ...... 
 
 ......  but, I think the whole point of the language of physics is, we all use exactly the same terms and definitions ........and exactly the same text ..... and that means the same words !!

 in early classes we all spent time repeating "definitions" parrot fashion in the classroom ad infinitum and rote learned ........ until finally it was drummed into us ....... so no matter where you go or whoever the scientist you talk to, the underlying meaning was never in doubt .

  ........ by the same token ........  I rarely use scientific terms in the French language ...... I just don't have the background in French school physics .... and I hardly know any French who have anyway ....
  
so I don't ....

It's a tough call to be a technical author of English physics ...... a trade all of it's own!! ....... and I'm certainly not up to it .......

[mst]

With any of the lenses discussed here, acutally all big tele primes (200/2 upwards) you'll definitely hold the whole setup with two hands, not just one on the camera