View Full Version : Asymmetrical, center and orbix tilt

21-Dec-2006, 00:18
What are the diffence between those? Is orbix tilt just front center tilt?
Which one of these is easy to use?

Leonard Evens
21-Dec-2006, 07:14
I have never actually worked with any of these, but I will give it a try. The issue is what remains in focus as you tilt. Wherever the tilt axis is, some horizontal line will remain in focus as you tilt, but it may be outside the field of view, so you will need to refocus after tilting. If the appropriate reference point in the lens is close to where the lens axis intersects the tilt axis, there will be only a small shift in focus for points on a horizontal line in the center of the field (assuming no rises). Center tilt is when the tilt axis passies through the center of the lensboard, and for some lenses the reference point in the lens is close enough to the tilt axis for practical purposes. I believe that the Orbix mechanism allows you to adjust things so the tilt axis does pass through the reference point, thus minimizing focus shift. I believe that asymetrical tilt places the tilt axis elsewhere so that some horizontal line other than that at the center of the field will remain in focus. It may be more useful in many situations to minimize the focus shift for such a line other than the center line.

I'm sure I got some of this wrong and will be corrected by others.

David A. Goldfarb
21-Dec-2006, 07:45
On the Sinar P cameras there are dotted lines on the groundglass to show where the asymmetric tilt and swing axes are. For tilt, you put the line somewhere in the desired plane of focus (using rise and shift if necessary), focus so that the area at the line is in focus, and rear tilt so that the rest of the plane of focus is in focus. The advantage of this method is that you can see it all happening on the groundglass without having to tilt, refocus, tilt, refocus, etc.

If you want the tilt on the front standard, then read the scale on the rear standard, apply the corresponding tilt to the front standard, and zero the rear tilt. Refocus (you should only have to do it once) and recompose using rise and shift if necessary.

Rakesh Malik
21-Dec-2006, 07:49
I'm not familiar with the Orbix tilt, so I'm only going to talk about asymmetric movements. As far as I understand it though, Orbix is essentially the same thing, but on the front standard rather than the rear.

Normally, when you use tilts, you have to choose between base and axis tilt. If you tilt from the base, you're moving the standard as well as tilting it, so it throws off your composition as well as your focus. With axis tilts, your composition stays pretty close to constant, but while the center stays in focus, the top and bottom of the ground glass go out of focus, so you have to go through a few iterations to get the whole image in focus.

With asymmetric tilts, you focus along the dotted line near the bottom of the ground glass, then lock your focus, and tilt until the image area along the dotted line near the top is in focus, and you're done. Asymmetric swing is the same concept, but left to right instead of up and down.

I hope that helps. I didn't really understand it until I tried it myself.

Emmanuel BIGLER
21-Dec-2006, 07:59
I can say a few words about the Arca Swiss Orbix® system.
In principle there is no difference between tilting around a visible axis located close to the centre of the lens and tilting with a device like the Orbix® which is based on the principle of circular goniometric stages in use in laboratory optics and X-ray spectrometers .

In the Orbix® used with a F-line camera, the radius of curvature is designed so that when the rise movement is zeroed, the effective rotation axis is located close to the optical axis. When using the lens rise, the rotation axis does not change since the lens goess up while the orbix stays where it is, at the bottom of the format frame, just above the function carrier.
This was just for geometrical considerations.

In terms of mechanical engineering, the Orbix® does not use classical dovetails like in goniometric stages, but another profile which requires less force to push on it hence allowing you to push on the stage and precisely set it manually (the manual or "dynamic" model) . You can of course use the geared ("micrometric") system but the Orbix® is self-locking, it means that you do not have to tighten any screw !! The system will not move except if you push precisely on the stage itself ot on the geared control knob.

Now one of the question is : which system is best: axis tilts, base tilts, symmetric or whatever ? My understanding is that there is no way to design a tilting system for view cameras that would be free from some drawbacks.
For landscape use, you would like to tilt around the exit nodal point to avoid that the image moves on the ground glass when you tilt, this position also yields a very small defocusing, but the position of the nodal point changes from one lens to another.
And if you shoot at 1:1 ratio the proper point that does not move the image is not the exit nodal point, in a symmetrical lens it is the centre of symmetry. So it is not possible to find an optimum rotation point fixed on the camera that would be universal for all purposes and all lenses !
Usually since most of our LF lenses are quasi-symmetric, the rotation point is located close to the center, i.e. close to the centre of mass, which has some advantages, the system being well balanced. With base tilts or assymetric tilts on a levelled camera, the required effort is minimum as well.

Frank Petronio
21-Dec-2006, 08:09
I've wasted 25 years of LF photography and thousands and thousands of crappy pictures because I never bothered to figure this out ;)

Asymmetrical tilt is a marketing term used by Ebony and Orbix is an marketing term used by Arca-Swiss. Sinar first got people concerned about this when they had to market their base tilt cameras (the standards tilt from the base) versus cameras which tilt around the center. Most Toyos, Horseman, Calumets, Cambos, Omegas, and other 1950s - 1980s monorails used center tilts, so Sinar tried to convince people that their base tilts were better.

The classic example is if you are doing a table top photograph of a wine bottle and some wine glasses and have tilted the camera down, placed the back vertical, and swung the standards to hold the plane of focus across the glasses and bottle, when you go to tilt the front standard you will introduce "yaw" into the camera's movements, leaving one corner less in focus than the other. Sinar's asymmetric tilts eliminate this possibility. In the 1980s Sinar's patents expired and Arca-Swiss and others (Ebony) started to do the same sort of thing.

Arca-Swiss's Orbix goes one step further by calculating the displacement of the arc that the tilted standard will move. But the reason many people prefer it is not for the geometric advantage -- it is indeed a beautifully machined and precise mechanism, whether you get the micro geared or friction versions.

There are many discussions debating center versus base tilts if your search, and then debates about the flavors of the base tilts (Orbix, Asymet, Sinar, etc.). Personally I don't think any of this matters one lick for practical photography, especially landscape photography instead of tabletop.

David A. Goldfarb
21-Dec-2006, 08:23
This is true. While the Sinar P makes certain kinds of still life work easier, and the yaw-free movements can really be a time saver with a shot that has multiple movements, a little experience will let you use the same moves for landscape quickly with any kind of camera.

Frank Petronio
21-Dec-2006, 09:06
Right, you probably will combine a swing, tilt, and fall in a classic tabletop shot all the time, and that is where a geared studio camera like the Sinar P has a nice time-saving advantage. Sinar really thought about how catalog and production photographers needed to work, and built a system for doing very precise yet fast photography.

And while you may occassionally use multiple movements for architectural work, more often you are doing a large rise and maybe a swing, with a little tilt, and you still need to stop down to carry enough depth of field to keep things in focus, rendering the slight -- if any -- extra advantage of the asymetrical movements worthless. But there always could be that one shot where they would make a difference.

If you ever do find that one situation let the camera companies know about it cause they've been looking for it too ;)

Rakesh Malik
21-Dec-2006, 09:24
There are many discussions debating center versus base tilts if your search, and then debates about the flavors of the base tilts (Orbix, Asymet, Sinar, etc.). Personally I don't think any of this matters one lick for practical photography, especially landscape photography instead of tabletop.

It's definitely not necessary, but I can say from using it that asymmetric movements are quite convenient, and I do almost all of my shooting outdoors somewhere.

I'd call it a luxury though, because though it's nice, you can without any doubt work without it. :)

Ole Tjugen
21-Dec-2006, 10:29
The main "variant" of axial tilt is still the "tunable axial tilt" where the tilt axis can be adjusted to pass through the lens' node (which is rarely exactly on the lensboard where the tilt axis is, but some little distance in front of it). Asymmetric tilt is a axial tilt with a fixed offset, IMO only the tunable axis makes a significant difference.