Arca-Swiss rail extensions

[Glenn Kroeger]

I am considering using a 300mm lens with an Arca-Swiss compact F-line camera so I will need a longer rail. I would love feedback on the available rail extensions, the 25cm version or the new 15cm version. I assume one uses these at the front standard end of the rail. Is it rigid enough to support a typical 300mm like a Nikkor-M or Fuji-C? Is it rigid enough for a true telephoto like a Nikkor 360T?

Thanks in advance

[Brian Kennedy]

Glenn - I use the 25mm rail extension with an A-S Discovery and the Nikkor 300M all the time. The rail extension is very solid. I'd say it's even solid enough to support even a heavy lens like a big 450, so your 300 will be no problem.

You slide it in the front of the rail (although I suppose you could stick it in the back, too), as it has a tube on one end that fits into the hole of the rail. Then you turn a knob on the end of it, and it grips the inside of the other rail. The way it is machined, it doesn't twist once it's installed. Maybe just barely if you torqued it really hard, but it certainly is solid enough.

With the extension installed, the ridges on the top of the rail are continuous from the other rail. In other words, you can move with the gears from the main part onto the extension and the standard travels from the original rail to the extension just fine.

[Eric Brody]

I also use the 25cm rail with my new F-line field and my new to me Nikkor 360T lens, which has a flange focal distance of 261mm @ infinity. The Nikkor 360 is a reasonably heavy lens at 800 grams. As Brian says the rail attaches quite firmly. My extension rail has a small flat area which requires a slight push from one set of gears to that on the rail but it's easy. It seems to work well. I have not yet tried it in a howling gale.

[Rory Roopnarine]

Hi Glenn,
The 25mm rail performs its functions well. However, realize that it is not meant to be removed once you attach it. I didn't know this when I bought mine. My nice foldable, compact rail suddenly became not so compact. I eventually traded in both my rail and the extension for a telescopic 50cm rail. Regards, Rory.

[Brian Kennedy]

Rory - are you sure? I've been attaching and detaching my 25mm extension rail for a few years without any ill effects that I've noticed. It still attaches solidly after being used many many times, and to detach, you just have to unscrew the end and pull it back out.

[Rory Roopnarine]

Now I'm confused! There is a little rod inside the extension that opens the jaws to grip the inside of the rail. Turning the screw clockwise pushes the rod forward, hence opening the jaws. However, when I try to turn the screw anticlockwise the rod doesn't move, and the jaws remain open. I was scouring the inside of the rail by attempting to remove the extension. Does this mean that my extension was defective and rod actually retracts when the screw is turned?

[Rory Roopnarine]

Humm, a little clarification. The rod pushes a pill-like bullet into the 'jaws' which opens them. The rod indeed retracts when the screw is turned anti-clockwise but leaves the little bullet in place and, hence, the jaws remain open. Was my extension working the way its supposed to then?

[Daniel Geiger]

I also use the 25 cm extension on a F-compact, and regularly remove it again. When you unscrew the extension knob you can pull the rail out quite easily. There is a bit of friction, both when you insert it, and when you remove, but I have not noticed any loosening of the joint.

I use it with my Nikor-T 360 as well as the 500; for the 720 it is too short, so I got a telescopic rail.