"Rated for 11 pounds."
"15 pound load capacity."
"12 pound weight capacity."
What do these figures mean when cited by tripod and head manufacturers?
Short answer: nothing particularly useful.
The first problem is that none of the manufacturers actually really disclose what test they're performing and what the criteria for that test are. The suspicion has long been that these are "break over" numbers. In other words, if you put a 13 pound camera on a 12-pound rating ball head at even a slight angle, the camera won't stay put: the friction on the ball head will be broken and your gear will go racing towards the floor.
But even if that's the number that's getting reported, it's mostly a useless number as it doesn't tell you anything about how steady the gear holds your camera and lens during a shot. I've found no good correlation between the ratings tripod makers give and the actual usefulness of the support they provide.
Here are Thom's Thests:
- No Recompose Test. Compose a shot with the camera/lens tilted at an angle. Lock down the legs and head. Did your framing move? The device fails the test if it does. Don't buy that gear. At a minimum you'll be frustrated with never getting the framing you've chosen, but the change is indicative of the fact that the support system isn't supporting well, either.
- The Finger Test. Put your camera with the longest lens you use on your legs and head. Frame something at a distance. Lock down the legs and head. Now make a big tap on the front of the lens hood with your fingers. Don't be gentle, your gear should be able to take a solid tap (but don't get carried away or you're likely to break your hood). See any up/down movement on the front of the lens? Yes? Then your gear fails. You can also look through the viewfinder while having someone (or yourself) tapping on the lens hood. If you see any unsteadiness through the viewfinder, that unsteadiness is likely to show up in your shots, too. Don't buy that gear.
- The Extended Test. Fully extend the legs of the tripod. Gently press in on the middle of the legs. If you can curve the legs at all, don't buy that gear. Okay, that's a little harsh. I do use one small tripod that has five leg extensions. When I extend either of the bottom two, I can curve the legs in my test. If I leave the bottom two sections unextended, the legs pass. That's exactly how I tend to use that tripod, which only reaches 36" when passing the test.
- The Have a Big Soft Pad on the Floor Test. It is important to understand just how far you can angle the camera/lens on your support before it tips. It's also a good indicator of how well the support handles wind gusts, too, as such things can have a similar affect of putting force off the center axis. But be careful doing this test. Originally I just screwed an Arca plate into a couple of different lengths of 6x6 lumber to do this, as I didn't care if I damaged the wood when the whole thing fell over ;~). But if you do this test with your 500mm f/4 and a D4 not well balanced and it hits your concrete floor, it's your repair bill, not mine. Really good support can tolerate a lot of off center weight before becoming unstable. But it's a good idea to know how much. I've seen far too many people putting big, heavy exotic telephotos on support gear that might work if the lens is kept level and the center of gravity is exactly over the center post, but fail completely in any other situation.
When I test tripods and heads, I do so with a vibration meter. I'll run through a series of shutters speeds, mirror lockup and not, looking to see how well and how fast the gear damps any vibration. That's what led me to my current tripod legs and head and away from the low-end stuff.