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Thread started 30 May 2012 (Wednesday) 18:55
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How "Max Load" of a ballhead was measured

 
pwm2
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Jun 12, 2012 01:09 |  #46

dlleno wrote in post #14566247 (external link)
One thing I found helpful is Markins' rating of both weight and torque, and the combination of these two numbers telegraphs their measurement/rating system. Let us accept Markin's own spec sheet that both of the following to be true at the same time (this is for the Q20):

max weight=110lbs
max torque= 220 inch pounds

now Then the measurement has to be made by hanging 110 lbs at 2-inches away from ball center. I imagine this is the absolute maximum torque that the ball can tolerate without either slipping or becoming damaged. not realistic at all, but it does give you a clue as to how to determine the real capability. Hats off to Markins for at least revealing this.

now then, the distance from the clamp itself to the ball center is approximately 2", but mount a real lens on there and you quickly see that 110 lb capacity disappear. for example, my 70-200 f/2.8 produces 5" of distance from lens center to ball center. This configuration would only support 44 lbs of camera+lens. 44 lbs times 5 inches = 220 pound inches.

so put a larger lens on there and measure lens center to ball center. divide 220 inch-pounds by this distance and you will have the absolute maximum weight of gear that the ball will tolerate.

Note that torque is computed using the distance perpendicular to the the direction of the force. When the camera gear is directly above the ball, the additional distance the lens is above the ball doesn't doesn't add to the torque - it's the horizontal distance between center of ball and center of gravity that generates torque.

When shooting macro and aiming on the ground - or shooting sky objects and aiming the gear straight up - your 5" will be the distance that matters.

So in the end, the type of photography done will affect how powerful ball head that is needed. People only shooting while aiming their gear horizontally don't need as strong/rigid head as if they shoot aiming straight down or straight up.

This is also a reason why gimbal heads can be very nice to use for heavy equipment, allowing it to swing up/down having the rotation axis much closer to the center of gravity. Easier for both the head and the user.


5DMk2 + BG-E6 | 40D + BG-E2N | 350D + BG-E3 + RC-1 | Elan 7E | Minolta Dimage 7U | (Gear thread)
10-22 | 16-35/2.8 L II | 20-35 | 24-105 L IS | 28-135 IS | 40/2.8 | 50/1.8 II | 70-200/2.8 L IS | 100/2.8 L IS | 100-400 L IS | Sigma 18-200DC
Speedlite 420EZ | Speedlite 580EX | EF 1.4x II | EF 2x II

  
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Islandhitman
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Jun 12, 2012 01:49 |  #47

cntangcn wrote in post #14564814 (external link)
Hi for the flash, 580ex II is on sale at $399 in Canada. You probably want to check that out.

The 430EX II is on sale as well.


Wendell - Living on the great island of Prince Edward Island, Canada:
60D | EF-S 18-135mm f/3.5-5.6 IS | EF 50mm f/1.8 II | EF 70-200mm f/4L USM |
www.redislephoto.com (external link)

  
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cntangcn
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Jun 12, 2012 07:32 |  #48

dlleno wrote in post #14566247 (external link)
One thing I found helpful is Markins' rating of both weight and torque, and the combination of these two numbers telegraphs their measurement/rating system. Let us accept Markin's own spec sheet that both of the following to be true at the same time (this is for the Q20):

max weight=110lbs
max torque= 220 inch pounds

now Then the measurement has to be made by hanging 110 lbs at 2-inches away from ball center. I imagine this is the absolute maximum torque that the ball can tolerate without either slipping or becoming damaged. not realistic at all, but it does give you a clue as to how to determine the real capability. Hats off to Markins for at least revealing this.

now then, the distance from the clamp itself to the ball center is approximately 2", but mount a real lens on there and you quickly see that 110 lb capacity disappear. for example, my 70-200 f/2.8 produces 5" of distance from lens center to ball center. This configuration would only support 44 lbs of camera+lens. 44 lbs times 5 inches = 220 pound inches.

so put a larger lens on there and measure lens center to ball center. divide 220 inch-pounds by this distance and you will have the absolute maximum weight of gear that the ball will tolerate.

Hi Dlleno, this is a very insight analysis and make a lot of sense to me. Thank you.

I regret I did not notice this information before. I guess only Markins disclosed this information, not others, not even RRS, correct?

While it is too late for my decision making, I would say I trust brands like Markins who dare to disclose these critical information and let end user to make decision, not by "feeling", but by number!

Cheers


5D MARK II, EF 24-105, EF 70 - 200 F4 IS, EF 50 F1.4, EF 40 F2.8, ZE 50mm MP, EF 24 F1.4 Mark I, Leica R50F2, Canon G10, Canon EOS M with 18-55 kit, Canon FL58F1.2, 270EX flash, 430EX II flash. Manfrotto 055XPROB + Sunwayfoto DB-44, Feisol 3442 (No CC) + Sunwayfoto FB-36DDH2

  
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cntangcn
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Jun 12, 2012 07:36 |  #49

pwm2 wrote in post #14566599 (external link)
...

This is also a reason why gimbal heads can be very nice to use for heavy equipment, allowing it to swing up/down having the rotation axis much closer to the center of gravity. Easier for both the head and the user.

good point! one more piece of equipment...photograph​y is really an expensive hobby...


5D MARK II, EF 24-105, EF 70 - 200 F4 IS, EF 50 F1.4, EF 40 F2.8, ZE 50mm MP, EF 24 F1.4 Mark I, Leica R50F2, Canon G10, Canon EOS M with 18-55 kit, Canon FL58F1.2, 270EX flash, 430EX II flash. Manfrotto 055XPROB + Sunwayfoto DB-44, Feisol 3442 (No CC) + Sunwayfoto FB-36DDH2

  
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dlleno
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Jun 12, 2012 11:00 |  #50

pwm2 wrote in post #14566599 (external link)
Note that torque is computed using the distance perpendicular to the the direction of the force. When the camera gear is directly above the ball, the additional distance the lens is above the ball doesn't doesn't add to the torque - it's the horizontal distance between center of ball and center of gravity that generates torque.

When shooting macro and aiming on the ground - or shooting sky objects and aiming the gear straight up - your 5" will be the distance that matters.

So in the end, the type of photography done will affect how powerful ball head that is needed. People only shooting while aiming their gear horizontally don't need as strong/rigid head as if they shoot aiming straight down or straight up.

This is also a reason why gimbal heads can be very nice to use for heavy equipment, allowing it to swing up/down having the rotation axis much closer to the center of gravity. Easier for both the head and the user.

correct, this is the reason why Markins lists torque separately from 'weight'. I'm sure you could put 110 lbs on the q20 (for example, or 100 lbs for the Q10) with no moment arm (perfectly plum), but since ballheads are often used outside of that operating point, the distinction is both obvious and important: the highest stress on the ball occurs in the drop notch at 90 degrees to plumb, where torque on the ball is highest due to gravity. when the ballhead clamp is perfectly plumb and the equipment balanced, torque is zero. The Q10 will tolerate 200 lb inches of force which, translated means that "in the drop notch":

1. 40 lbs at 5 inches from ball center
2. 33 lbs at 6 inches from ball center
3. 28 lbs at 7 inches from ball center

Given that these are absolute maximums, one is advised to de-rate by a factor of two (some say more, but since we have a real number from Markins, unlike other mfgs, 2x is sufficient imho).

ok so you de-rate to approximately 14 lbs at 7 inches from ball center -- an astonishing condition in its own right: A pro series body is ~3.5 lbs which means you have 10.5 lbs of room for a long super tele into the 600mm f/4 region + a TC. I'm being conservative here because I don't know the actual 'lens center to ball center' afforded by the Canon 600mm f/4, which weighs in at less than 9 pounds.

But, as you rightly implied, no one really carefully maps out a plan to use a ballhead in this way -- if you have that equipment you should be using a full gimble head. Even the Wimberly sidekick, which should be a fine addition to the Q10 or 20, will drastically reduce the "moment arm" or twisting force (torque) on the ball for the reasons you point out.

In conclusion, the Markins Q10 or Q20 should be capable of anything one would normally use a ballhead for, and the addition of the wimberly sidekick would be a fine solution for the likes of 300mm f/2.8+TC and 500mm f/4+ TC. Incidently, I've used the latter with a std ballmount and vowed never to do it again :D


5D mark iii, EF-24-105mm f/4, EF 70-200 f/2.8L IS II USM, Speedlite 580 EX II plus 3x Yongnuo 568EX, photoflex 60" white umbrella, Westcott Apollo Orb with grid

400mm on a 1.6x body is still 400mm. sensors do not change lens physics...

  
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M635_Guy
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Jun 13, 2012 03:52 |  #51

I own both the RRS BH-40 and the Sunwayfoto XB-44 (which they provided to me for review when I responded to a call for volunteers).

My impressions of the Sunwayfoto head were VERY positive. It is less than the BH-40, but not by much. I agree with you on the all-metal construction - the thing feels military-grade.

Here's my full review:
http://enthusiastphoto​grapher.com …o-xb-44-ball-head-review/ (external link)

I like it just as much as the RRS, maybe slightly better since the flap-paddle design of the RRS bugs me a little sometimes...


My blog: Enthusiast Photographer (external link)
My Flickr: http://www.flickr.com/​photos/e24mpwr/sets/ (external link)

  
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cntangcn
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Jun 13, 2012 07:56 |  #52

M635_Guy wrote in post #14572128 (external link)
I own both the RRS BH-40 and the Sunwayfoto XB-44 (which they provided to me for review when I responded to a call for volunteers).

My impressions of the Sunwayfoto head were VERY positive. It is less than the BH-40, but not by much. I agree with you on the all-metal construction - the thing feels military-grade.

Here's my full review:
http://enthusiastphoto​grapher.com …o-xb-44-ball-head-review/ (external link)

I like it just as much as the RRS, maybe slightly better since the flap-paddle design of the RRS bugs me a little sometimes...

I was looking at the sunwayfoto XB-44 but their distributor in Canada does not carry that model yet...

I have got my DB-44 a few days ago. first impression it looks great. haven't tried in field yet. waiting for my tripod to come...


5D MARK II, EF 24-105, EF 70 - 200 F4 IS, EF 50 F1.4, EF 40 F2.8, ZE 50mm MP, EF 24 F1.4 Mark I, Leica R50F2, Canon G10, Canon EOS M with 18-55 kit, Canon FL58F1.2, 270EX flash, 430EX II flash. Manfrotto 055XPROB + Sunwayfoto DB-44, Feisol 3442 (No CC) + Sunwayfoto FB-36DDH2

  
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dlleno
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Jun 13, 2012 11:40 |  #53

cntangcn wrote in post #14567392 (external link)
Hi Dlleno, this is a very insight analysis and make a lot of sense to me. Thank you.

I regret I did not notice this information before. I guess only Markins disclosed this information, not others, not even RRS, correct?

While it is too late for my decision making, I would say I trust brands like Markins who dare to disclose these critical information and let end user to make decision, not by "feeling", but by number!

Cheers

yes cntangcn I too prefer actual numbers that make physical sense, and I make purchases based on things I understand, instead of feelings

It is interesting to try and figure out what a manufacturer's goals are with a published spec. Being rather geeky myself I place a higher value on a mfg that publishes specs I can understand and relate to in the real world. Thus, while I'm sure they are conservative, sufficient and accurate enough, I have no idea where RRS gets their numbers, while the Markins numbers make perfect sense to me -- even if they require a little physics to interpret.

thats said I suspect Markin's goal is to publish a big number so that people who compare numbers will be impressed. It should be pointed out that no real photography situation is capable of loading the Q10 with 100 lbs of weight at 2 inches from ball center, so some might get irritated that the number is deceiving. I on the other hand, look at the torque spec and see what is really going on, so I have confidence in how the numbers are derived.

In studying the Markins and RRS heads I've pieced together another interesting observation that explains the real world comments consistent throughout the reviews. I note that the Markins is consistently described as smooth and "with a sweet spot" ,and the RRS is consistently described as solid. conversely, the RRS is rarely described as having a smooth sweetspot, and the Markins is always described as having a solid lock.

looking at the design I now see why: the RRS pinches the ball from the side, a method guarenteed to apply a very miniscule amount of non-uniform clamping force to the ball during the pinch. such as design is inherantly less capable of "smooth sweetspot" operation but inherantly capable of a very high clamping force and solid feel. So -- those for whom the "smooth sweet spot" is less important will find the RRS design is quite satisfactory.

The Markins, on the other hand, appears to raise the ball up from the bottom ,squeezing it into the upper 'clamp' which itself does not move and is uniformly matched to the ball geometry.Reading in between the lines again, the Markins "bi-lateral" language probably means that the mechanism that raises the ball from the bottom is a geometry much like the top side -- thus, you have a true, uniform "squeeze" more likely to provide a smooth sweet spot, than the RRS "pinch" design.

Incidently, the inherant (non-spherical ball) design of the Arca-swiss z1 ballhead gave me pause as well, as this one to me could be inherantly more prone to lockup problems if the mfg tolerances are not absolutely perfect. A-S appears to have solved this problem and hats off to them for doing so; its just that from a theoretical perspective the Markins design is most appealing to me, as a combination of reliabilty, simplicity, and performance. I even like the maintenance suggestion to use WD-40. It makes thigs more practical and real to me and puts more control in my hands instead of elevating the product to untouchable halo magic status.

now I just need to translate theory into practice and get one of these things!

on Edit: In case the above comes across as some bias against RRS, please note that I have the RRS MH-02 pro monopod head, and find it to be without a doubt the best monopod head on the planet, and highly recommended!


5D mark iii, EF-24-105mm f/4, EF 70-200 f/2.8L IS II USM, Speedlite 580 EX II plus 3x Yongnuo 568EX, photoflex 60" white umbrella, Westcott Apollo Orb with grid

400mm on a 1.6x body is still 400mm. sensors do not change lens physics...

  
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How "Max Load" of a ballhead was measured
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