Arca swing and tilt precision

[Hening Bettermann]

Hi!

I consider replacing my pre-1984 6x9 Arca with the current F-line. Yaw-freeness and the micrometric Orbix® are the attractions, even though the weight would go up a little.

I have 2 reservations:

1- Martin Voigt told me on the phone, that the micrometric Orbix has indents ("Kugelrasten") every 3 degrees. If I think of the 90 degrees indents on the tilt and swing on my Arca, the small angles in the nearness of the indent are tricky if not impossible to set, because the standard has the tendency to snap into the indent.

Can Arca users of the micrometric Orbix comment on this?

2- My precondition is that I want to *calculate* the tilt and swing angles. I want to be able to set angles in the size of the lower values on the Rodenstock calculator, which means I want to be able to adjust the movements to a fraction of a degree. The scale for the swing has a scale of 5 degrees intervals on a pretty small radius. Even with visual interpolation, this would not do. Furthermore, on a photograph of the F-line, the swing scale on the front standard looks like it is almost invisible under the "lip" of the frame clamp.

Martin Voigt said in the phone there would be no place to attach a worm drive to that swing. On my old Arca, my machinist says he could easily mount such worm.

Do I have to choose between yaw-freeness and a visible and operative swing scale? Any bright ideas?

Kind regards -

[resummerfield]

I have the Metric geared Orbix, and while I note the detents, the standard is very easy to adjust and does not “snap” into the detent. However, there is no reference scale on the Orbix to indicate degree of tilt.

[Hening Bettermann]

Thank you. - Martin Voigt said in the phone that on the micrometer screw, 1/4 turn equaled 3 degrees, and that the turning knob had a diameter of about 1,5 cm. That would make it possible to paste a usable scale on the periphery of the knob. But would there be a place to install the zero mark?

Kind regards -

[resummerfield]

My Orbix turning knob is 24mm diameter, and there are 5 detents in a complete turn of my knob. So I re-read your original post and noted that your interest is in the 6x9, and I have the 4x5 with the 141 front standard. However, both models should share similar traits.

On mine, the bottom of the standard's dovetail is in line with the knob center, and would make a good reference. There is very little backlash in the gearing, and I would guess you could be accurate to 1/2 degree.

[Frank Doering]

The orbix doesn't snap into the detents. If you find the Arca swing indents problematic, you haven't wrestled with a Technikardan.

The joints on the arca are all quite compact. As a result, any scale attached to them is going to be way too imprecise for your purposes. I once tried to go down that route and decided that focusing by groundglass inspection with some interpolation by feel was much more precise.