What's this for?

[alanworland]

I have spent some time today removing the quick release base from my tripod and adapting it to fit my monopod, so that I now have a quick method of attaching my camera to either.
It was while doing this that I wondered why normal tripod/monopod screw type mounting pads have a spring loaded plunger which protrudes out of the top surface - any ideas?

[Fen]

Not all cameras have the same size screw thread.

The outer thread (the one that pushes down) is for larger cameras, Medium Format and that sort of stuff

[alanworland]

Thanks - you learn something everyday!

[Barney]

I think the OP is referring to a secondary pin on the plate whihc sits in front of the screw thread, which I can only presume is there to help prevent the plate twisting as you tighten it. I can't think of any other reason.

[Barney]

Thanks - you learn something everyday!

Maybe not then!

[Fen]

Unless he means the locking switch...

[alanworland]

I was trying to describe the spring loaded pin which is about 1/2 inch from the screw thread.

[alanS]

Isn't the pin for a camcorder?

I'm sure I had a still camera in the past that also had a hole for the spring loaded pin, I think it was a Fuji S602 but I can't be sure.

[Barney]

I was trying to describe the spring loaded pin which is about 1/2 inch from the screw thread.

That's what I thought you meant.

[JJM74]

I think the OP is referring to a secondary pin on the plate whihc sits in front of the screw thread, which I can only presume is there to help prevent the plate twisting as you tighten it. I can't think of any other reason.

That's my thought too. My Camcorder has a socket about there, but none of my cameras, tripods or QR plates do. I always assumed the hole in the camera was to accommodate an extra pin to prevent it rotating.

[Malcolm_Stewart]

...My Camcorder has a socket about there, but none of my cameras, tripods or QR plates do. I always assumed the hole in the camera was to accommodate an extra pin to prevent it rotating.

Yes, I think they're called "video pins".
Annoyingly, I've got a head where the pin is stiff, and it gouged a scratch in the base of what had been a mint camera base up until then. I note that my camcorders have a more hard-wearing material around the tripod socket.

It would be useful if the longer lenses fitted with tripod feet had the extra hole. Not all tripod screws are that easy to tighten adequately. (Thinking 300mm here.)

[zx9]

It would be useful if the longer lenses fitted with tripod feet had the extra hole. Not all tripod screws are that easy to tighten adequately. (Thinking 300mm here.)

Time for a little DIY, now where did I leave the Black and Decker?

[Manofolympus]

Must admit I remove the things as they tend to get in the way and are no use!-at least for still cameras

[Staropramen]

The small pin is to prevent camcorders and 'scopes slewing (twisting) as the device is panned, especially when mounted on a friction/fluid head which has some movement tensioning. This is usually unnecessary for smaller still cameras, but the approach is used on a few (heavy) medium format cameras and on some ultra telephoto lenses. Some cheaper tripod systems use a fixed spring-loaded pin, others (e,g, Manfrotto) often have a more permanent, screwed-in (and removable/reversible) pin.