Wed 06-Feb-13 10:56 AM | edited Wed 06-Feb-13 12:22 PM by agitater
>I understood that it was really going to be a matter of torque >rather than weight. But there must be a maximum wieght which, >when the camera is in a position to maximize torgue, would be >safe. For example a speedlight is going to maximize torque on >the hot shoe in certain positions, so I hope if something >weighs less than an SB900 speedlight, then it would be safe to >mount it on the hot shoe.
I think the maximum amount of weight of something that is mountable in the hot shoe is quite high mainly because the shoe is supported by the internal metal camera frame. But it is my understanding that, during prototyping, the stress testing of the hot shoe is primarily about applying lateral force to a mounted item to ensure studs which secure the shoe in position can withstand commonly applied torque. I think "commonly applied torque" is defined as high winds hitting a full size strobe with a large diffuser (e.g., a Garry Fong model of some sort), incidental elbowing and other accidental impacts, and I think the test maxes out at about 13.5Nm. I do not recall the source of that 13.5Nm test limit, and I also believe the hot shoe is actually rated to withstand more torque than that. Nikon technical service might be the best source for precise ratings.
My own experience in the field includes an SB600 torn off its mount due to a strike by a protester's wooden picket. The hot shoe did not budge and continued to work properly after I removed the remains of the SB600 base and mounted a different flash. The impact took place at relatively high speed. I cannot determine if the the same total amount of lateral force applied more gradually would cause the hot shoe to tear out of its own mount before the base of the strobe failed.
The determination of maximum hanging weight (e.g., how much hanging weight the hot shoe can safely tolerate when something is mounted and the camera is being used in vertical orientation, or if the hot shoe is used to attach an assembly from which the camera is then hung or suspended) may be a crapshoot unless someone has an dead, older DSLR with an internal metal frame and the owner is willing to sacrifice the camera in a test. Even then, without service manuals it might be difficult to determine if Nikon is using the same hot shoe assembly method in the D800 as it is in some older DSLR sacrificed for testing.
Anyway, my suggestions are a) that applying anything more than 13.5Nm of hanging force or lateral force to the hot shoe might be damaging, and b) rapid lateral impact to a mounted strobe is more likely to tear the strobe off its mount than damage the hot shoe. I think it makes sense to consider that the hot shoe is only as strong as the screws or bolts or studs/retainers or T&G machining used to hold it in place.
In the damage-causing incident mentioned above, I estimate the weight of the picket to have been approximately 800 grams, traveling at approximately 7 meters/second. (UPDATED: I think that works out to 11.2 Newtons of force)
If you can tell us what you're considering mounting, you might get the attention of a Nikonian who has already tried it. Nikon technical services might also be able to tell you whether or not the item(s) you're considering mounting in the hot shoe are safe to use in that way.