Arca-Swiss Micrometrix Orbix and Yaw

[overconfidence]

Hay guys, first post here! I've been looking at the Arca Orbix mechanism, which is supposed to be "triaxially yaw-free". However, from what I've seen online (this image (http://img690.imageshack.us/img690/2458/orbixaction.jpg) and this video (http://www.youtube.com/watch?v=bDZwLNTne2U) are about all I can find), I don't see how this is possible.

By my understanding, any time you have the tilt movement above swing, you're going to get yaw (since the front standard will not be vertically parallel to the rear standard). I don't see how this problem is avoided by the Orbix, since the swing movement appears to be below the whole Orbix tilting mechanism.

Is this somehow avoided because the lens is still centered optically after the movements? Would most other view cameras then also be considered triaxially yaw-free as long as the tilt and shift occur around the center of the lens and no displacement movements are applied? Or does the Orbix stop being yaw-free if shift or rise are applied (I assume these can still be used on the Orbix standards)? And if that is true, then what happens when rear displacement movements are applied?

From what I can see (from the limited images of this mechanism online), application of both tilt and swing on the Orbix would be equivalent to this (http://img196.imageshack.us/img196/6142/yaw1.jpg) - the only difference being that tilt is coming from the base (but still having the same overall effect as if it weren't, since the swing movement is below it) ... but to me there is still yaw (http://img38.imageshack.us/img38/6538/yaw2.jpg), unless my understanding is flawed.

I'm not certain if swing is somehow above tilt, or if having the movements occur around one common point eliminates yaw (but then, isn't this also true for most view cameras unless you apply displacement movements?). Any clarification on this would be great - I'm probably missing something silly, but online documentation for most of the Arca-Swiss stuff is pretty scarce.

Thanks!

[JimL]

My understanding is that yaw free means that the swing axis can be adjusted to vertical when the rail is not horizontal. On most cameras the swing axis is fixed to be perpendicular to the rail. When you tilt the rail, the swing axis tilts, and the angle between the standard and the horizontal plane (whether 90 deg or some other angle) will vary as swing is applied. Looking at the video, there's an angle scale for base tilt just inboard of the gray lever. If indirect rise or fall is applied by tilting the rail, the swing axis can then be brought back to vertical using base tilt. The swing axis is right above the base tilt mechanism. It's really the base tilt below the swing axis that makes the camera yaw free, not the Orbix. Unless indirect rise or fall combined with tilt was required for some precise technical shot, I wouldn't consider this to be a terribly essential feature.

[overconfidence]

Thanks for the response! I came across other (http://www.b3kdigital.com/images/ArcaSwiss-solution.pdf) documents (http://www.precisioncameraworks.com/Media/Syst.pdf) which actually pinpoint the Orbix mechanism as the reason behind this standard having tri-axially yaw-free geared movements. I am fairly certain the base tilts on the F-line Arca bodies are not geared. This may be different on the M-monolith (as pictured in one of the documents), but I don't believe the implication of "Orbix" would change from camera to camera (maybe it does?).

From that document, it appears that if you apply any vertical displacement movement (rise) or horizontal displacement movement (shift), the Orbix will no longer be yaw-free, since it will no longer be rotating around the optical center of the lens. The document seems to say that the whole Orbix action occurs above the vertical displacement axis, but I don't see how this translates to the F-line standards, where the Orbix base does not move when rise or fall are applied. To me, it looks like you have to (1) frame your image using rear displacement movements and angling/etc of the camera and then (2) apply tilt or swing movements as desired. If any front displacement movements are applied to the F-line Orbix standard, then the lens will not be moving about its optical center and therefore the camera will yaw, correct?

If this is true, then won't most other view cameras be tri-axially yaw-free as long as only rear displacement movements are applied for framing? For example, looking at the Horseman LE (http://img130.imageshack.us/img130/8190/kty3387.jpg), it appears as if you could even apply front rise or fall and still maintain rotation around the lens axis (as long as no front shift is applied). Anybody care to comment on this? :)

I suppose front displacement movements are not strictly necessary, but they do become useful when a great deal of movement is required. In that case, I do not believe there is a geared option within the F-line that allows yaw-free movements for these situations (except perhaps turning the Orbix on its side).

I agree in that having perfectly yaw-free movements is not essential feature for all view cameras, but I am in the process of sketching up a camera myself and having the option of being yaw-free is something I am looking into.

[Leonard Evens]

I haven't yet studied everything above, so I'm not sure just what you want to know, but let me add one point about `yaw' which is often msiunderstood.

The difficulty is that `yaw free' can mean different things.

It can refer to a rotation of the standard about an axis perpendicular to it. In that case, it is irrelevant for the front standard, since lenses are symmetric about their axes. For the rear standard, it may be important because usually you want the top and bottom of the rear standard horizontal.

The second meaning is only loosely related to the technical meaning of yaw in other fields. It refers to what happens to the exact subject plane as you tilt and swing. It would be desirable, for example, to be able to obtain a desired exact subject plane by tilting first and then swinging (or vice versa). This is in principle always possible if you are willing to make detailed measurements and use complicated formulas. But if you want to do it based on what you see on the gg, it is another matter. It is possible to do this with tilt followed by swing if the swing axis is not moved by the tilt. But if the swing axis moves with the standard, as is usually the case with base tilat, then you can't do it in a single tilt/swing operation. You have to go back and retilt after the swing, reswing after the second tilt, etc, continuing to iterate until you get what you want. (The situation is similar for swing/tilt except that the issue is whether or not swing affects the tilt axis.)

See
www.largeformatphotography.info/forum/showthread.php?t=35036&highlight=yaw
for a longer discussion.


There seems to be a belief that the two meanings are the same, i.e., that by eliminating yaw, you also eliminate the focusing problem, but that is not the case. The two issues are independent of one another. The focusing problem can arise whether or not the camera is yaw free in the first sense. However, because of phsyical limitations of how tilt and swing are accomplished, the two problems often go together.

I believe the issue for the orbix is the focusing question since the orbix mechanim is typically on the front standard for which yaw in the sense of roatation of the standard is irrelevant. It turns out that for the focusing problem the crucial issue is the following. After a tilt, you will have a certain hinge line below the lens. To make things easier, you want the swing to rotate the hinge line about some point contained within it. But it might also translate it so that no point remains fixed. In that case, you have to go back and readjust the tilt. I think the orbix mechanism may ensure that the swing will just rotate about a fixed point in the hinge line.

[Lee Christopher]

If this is true, then won't most other view cameras be tri-axially yaw-free as long as only rear displacement movements are applied for framing? For example, looking at the Horseman LE (http://img130.imageshack.us/img130/8190/kty3387.jpg), it appears as if you could even apply front rise or fall and still maintain rotation around the lens axis (as long as no front shift is applied). Anybody care to comment on this? :)


I'll admit that the technicalities stump me, but I remembered this document. Hope it helps.

http://www.komamura.co.jp/e/L45.html

[overconfidence]

Thanks for the link - I'm pretty sure this sums it up:



For example, my Arca 4x5 w/orbix is yaw free. I can use base tilt to bring the front/rear standard back to vertical. When the standard is vertical, the swing movement pans around on a purely horizontal plane. I can then use the orbix tilt movement (axial tilt above the base tilt and swing movements) to dial in additional front tilt to go with the swing.

This is the same for most view cameras with base tilts - there is a separate tilt function at the lens axis as well. I knew I was missing something, and that pretty much summed it up. Thanks!