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02-25-2016, 01:51 PM   #1
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Anti-rotation Pin and the Socket on A* 600mm f/5.6 Foot

As some of you know, the SMC-A* 600mm f/5.6 has a short tripod foot that is well aft of the centre of balance of this lens with mounted camera body. This necessitates a longish quick-release plate to balance the lens/camera combo. The tripod foot has the 1/4" threaded socket for the tripod mounting stud (screw). In addition, there are two unthreaded sockets, one fore and one aft of the threaded socket. I assume these are meant to accept the anti-rotation pin (also known as "vhs location pin") found on some tripod heads and quick-release plates. This pin prevents the camera from unscrewing itself from the mounting stud if either: a) the user rotates the combo by rotating the camera, or b) when the combo is hoisted onto the shoulder for transporting the apparatus on foot.

I have a problem to solve involving these sockets and the anti-rotation pins that are meant to fit into them. I have the Manfrotto 501pl and 501plong plates (14 cm long). However, the anti-rotation pins on these plates are too large in diameter to fit into the sockets on the A* 600m f/5.6 tripod foot. On my spotting scope I simply drilled the socket out to fit the pins. However, I am reluctant to do the same to the 600mm. Are there pins of narrower diameter available? If so, are there any available that will fit into Manfrotto plates?

I have also noticed that the distance between the threaded socket and the anti-rotation pin sockets differs between the spotting scope and the 600mm. On my plates, the anti-rotation pin slides along with the mounting stud. The distance between the two is the same as the sockets on the spotting scope foot but not on the lens foot. This means that I have to mount the plate onto the lens's tripod foot without the anti-rotation pin, making the lens/camera combo susceptible to loosening on the mounting stud. Depending on the tripod head used, plates on which the mounting stud moves independently of the anti-rotation pin might not be available. Do you have any bright ideas about how to solve this?

02-25-2016, 02:26 PM   #2
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Interested in this also. Been trying to figure out what plate or whatever you were supposed to be using back when it came out. I really really wish it had two screw holes and one of them was a 3/8" instead of a single 1/4". Also notice if you put a long enough plate on it to balance it, the plate will impede the focus lock thumbscrew thing. I worked out a double plate system to get a little distance there.

And then recently got a fancier long lens support gadget, but haven't quite figured out how to use it on that lens since it has no real foot -- needs an extension and I'm back to wondering the same thing you are -- isn't there something I can get that will at least fit in these pin holes? Pretty amazing that the arca-swiss type plates and similar are such a recent invention. How the hell did they even use to balance this monsters? Just more-or-less bolted on to giant tripods I guess...
02-26-2016, 12:24 PM   #3
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I have the same question. I believe the pin on Manfrotto 501pl is called "video pin, which has larger diameter than the holes on Pentax tripod foot. I myself have a Giotto plate that also features such video pin. Unfortunately, it won't fit for my Pentax lens. What standard does Pentax follow as far as this pin concerned? There's got to be a standard - may not be a standard for video equipment but has to be one for photo equipment, right?

Last edited by hyyz; 02-26-2016 at 12:35 PM.
02-26-2016, 12:36 PM   #4
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Was anybody using quick-release plates at all when this lens came out? I sold my A* 300/2.8 -- can't remember if it had the same holes, but it was similar. I noticed Mayima medium format cameras (for the body) have a similar set-up, but their pin holes are 50mm apart -- these on the Pentax lens are about 41mm if I remember correctly.

Seems like Clinton ought to know something about this?

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anti-rotation pin, combo, foot, k-mount, pentax lens, pin, pins, plates, slr lens, socket, stud, tripod
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