Arca M-Line 2; Is It Yaw Free

[JoeKitchen]

Just out of curiosity (not going to go out and buy one) is the M2 yaw free? 

If it does have a yaw, how bad is it?

(I never understood the importance of yaw-free tilts and swings until doing table top photography.)

[Theodoros]

The importance of yaw free operation is much more than most people think... Especially when the subject is close or for interior architecture photography and even more so if stitching is involved. Literally, no image is distortionless unless if the camera is completely yaw free and the lens is completely free of distortion. The result out of using a "perfect" combination, won't only be successful and distortionless, but sharper too as there will be no "mud" added due to stitching... Further more, if the camera is completely yaw free, one can use stitching by rotating the camera around the axis that passes through the lens entrance pupil and other than achieving much wider angles, use swings between shots as to achieve an impressive result for perspective.

For completely yaw free operation to be achieved, the lens entrance pupil must be positioned at exactly at the center of  the circle of which the tilt arc is part of the perimeter and then the swing movements mechanism center to be on the same axis as the entrance pupil of the lens and the center of the tilt arc... Therefore, for the M2 or other camera to be yaw free, it is not a matter of camera design, but more a matter of lens positioning on the frame.

Ideally, for a camera to be of completely yaw free operation with any lens attached on it, the front and rear frames should be adjustable back and forth on the standard so that the user positions the frame so that its entrance pupil is at the correct position despite the lens used (of course the same applies for the center of the image area on the rear frame) and additionally, if the camera has shift mechanisms on the same standard, up-down shift mechanism should be UNDERNEATH the tilt mechanism and side shifts should be underneath the swing mechanism... otherwise combination of these movements should be avoided because they'll destroy yaw free operation.

Personally, I use a Sinar P2 (one of the few cameras that have all shift mechanisms bellow all tilts and swings) and have the frames and bellows completely removed and replaced by new ones that can slide back and forth on the standards, got rid of Sinar's parallel axis system (the new frames are centered), I use a self made bellows that can squeeze to less than 5mm and can extend to 400mm and used circular frames of Φ 85mm  for the front standard and Φ 72mm for the rear standard so that I can even mount a Sony mirrorless and have its grip recessed by the frame... I've also converted a Kapture group sliding frame and mount it on the rear frame's external diameter (Φ82mm external -72mm internal) so that the image area of an MFDB is also operational on the rear frame.

[Theodoros]

If it does have a yaw, how bad is it?

That depends...., for the same distance of entrance pupil wrong positioning, the camera with the shorter tilt arc radius creates more error.

(I never understood the importance of yaw-free tilts and swings until doing table top photography.)

This is because the principal behind yaw free operation is the same as with panoramic photography, the more distant the subject, the more distortions are hidden. With internal architecture, other than having distortions if one stitches a near WA subject by using rear frame shifts, he'll additionally be unable to create a wider angle by rotating the camera around the axis line that the tilt arc's center and swing center is part of.

It is important to note that one can (completely) correct yaw errors by making his own lens boards for each different lens he uses and his own image area mounting board on the rear standard. Then, he only has to care that all shift mechanisms are bellow the tilt/swing ones on his camera.

[torger]

Regarding the actual camera, Arca M-Line 2 (or "M-two MF" or various other combinations, it's never been really clear to me what the camera is actually called...), it has the Orbix so it's supposed to be "yaw free". But as in any camera this is approximate. I don't know if it worse or better than any other "yaw free" camera in this regard though.

[Chris Barrett]

The base tilt of the Oribx rotates around the center of the lens board.  The camera is effectively yaw free.  If, as Theo points out, you have a lens with an entrance pupil that happens not to be centered on the plane of the lens board, then that throws everything out the window (on any existing commercially available camera).

-CB

[BobDavid]

The importance of yaw free operation is much more than most people think... Especially when the subject is close or for interior architecture photography and even more so if stitching is involved. Literally, no image is distortionless unless if the camera is completely yaw free and the lens is completely free of distortion. The result out of using a "perfect" combination, won't only be successful and distortionless, but sharper too as there will be no "mud" added due to stitching... Further more, if the camera is completely yaw free, one can use stitching by rotating the camera around the axis that passes through the lens entrance pupil and other than achieving much wider angles, use swings between shots as to achieve an impressive result for perspective.

For completely yaw free operation to be achieved, the lens entrance pupil must be positioned at exactly at the center of  the circle of which the tilt arc is part of the perimeter and then the swing movements mechanism center to be on the same axis as the entrance pupil of the lens and the center of the tilt arc... Therefore, for the M2 or other camera to be yaw free, it is not a matter of camera design, but more a matter of lens positioning on the frame.

Ideally, for a camera to be of completely yaw free operation with any lens attached on it, the front and rear frames should be adjustable back and forth on the standard so that the user positions the frame so that its entrance pupil is at the correct position despite the lens used (of course the same applies for the center of the image area on the rear frame) and additionally, if the camera has shift mechanisms on the same standard, up-down shift mechanism should be UNDERNEATH the tilt mechanism and side shifts should be underneath the swing mechanism... otherwise combination of these movements should be avoided because they'll destroy yaw free operation.

Personally, I use a Sinar P2 (one of the few cameras that have all shift mechanisms bellow all tilts and swings) and have the frames and bellows completely removed and replaced by new ones that can slide back and forth on the standards, got rid of Sinar's parallel axis system (the new frames are centered), I use a self made bellows that can squeeze to less than 5mm and can extend to 400mm and used circular frames of Φ 85mm  for the front standard and Φ 72mm for the rear standard so that I can even mount a Sony mirrorless and have its grip recessed by the frame... I've also converted a Kapture group sliding frame and mount it on the rear frame's external diameter (Φ82mm external -72mm internal) so that the image area of an MFDB is also operational on the rear frame.

Excellent explanation. Now I've got a razor sharp conception of how it all works. Does the Cambo Ultima work well?

[Theodoros]

Regarding the actual camera, Arca M-Line 2 (or "M-two MF" or various other combinations, it's never been really clear to me what the camera is actually called...), it has the Orbix so it's supposed to be "yaw free". But as in any camera this is approximate. I don't know if it worse or better than any other "yaw free" camera in this regard though.

The Orbix on the MF2 (or other Arca) is useful only if one uses a lens that has its entrance pupil positioned exactly on the board's plane. If a retrofocus MF lens is used, the error will be more than other cameras that have the tilt mechanism on a parallel plane to the lens board.

EDIT: Sorry, I did the reply before I saw that Chris has already said the same, no disrespect meant... Sorry Chris.

[Theodoros]

Excellent explanation. Now I've got a razor sharp conception of how it all works. Does the Cambo Ultima work well?

Hi Bob, thanks!

The Ultima has one design flaw... it's got the side sift mechanism above the swing one... This means that if one combines the two, swinging the lens will be on the perimeter of a circle that the side sift value is a radius of (provided that the entrance pupil is correctly positioned for yaw free operation), so it is best that one swings on one standard and side shift on the other... never combine the two movements on the same standard.  OTOH, the Ultima is the easiest among all cameras to convert for correct lens and image area positioning... it's got the slots ready for you in the direction needed! 

[JoeKitchen]

Thanks Guys, I appreciate the response and thoroughness. 

[Theodoros]

An easy way to make a camera completely yaw free, is if one makes his own lens boards for that camera... It really is of worth for every bit of the effort put into it... The process is as follows...

Mount the lens (each different lens) on a lens board and follow the "usual" process as to "find the nodal point"...,  meaning that you have to set two bars at 10 & 20 meters apart and then rotate the whole camera system on a tripod by moving it back and forth (no movements applied on any on the standards) until the furthest away bar is completely out of vision...

Then calculate the distance between the lens mounting plane and the plane on which the rotation axis of the whole system is part of... mark this number, and then CUT your lens board so that the lens mount is separated from the rest of the board... then machine a spacer as long as the distance marked and use it as to recess (positively or negatively) the lens mount with respect to the original mounting board... That's it!  As long as your shift mechanisms will be UNDERNEATH your swings or tilts, your camera will be completely yaw free... (with the lens used for the test... the process has to be repeated for every lens one uses... For the rear standard, make sure that your image area is positioned at the plane that is crossing the center of the tilt arc....

[Chris G]

If it does have a yaw, how bad is it?

According to the Scheimpflug rule the optical planes must be intersect in a line - not just a point. That, is possible only with a yaw-free camera (in scenario "dual sharpness distribution control in a plane incident in two directions").

(I never understood the importance of yaw-free tilts and swings until doing table top photography.)

Indeed, the tabletop photography is the main field where yaw free design shows the real benefits and the best way to understand this someone, is practical training, after the correct theoretically knowledge.

The importance of yaw free operation is much more than most people think... Especially when the subject is close or for interior architecture photography and even more so if stitching is involved. Literally, no image is distortionless unless if the camera is completely yaw free and the lens is completely free of distortion. The result out of using a "perfect" combination, won't only be successful and distortionless, but sharper too as there will be no "mud" added due to stitching... Further more, if the camera is completely yaw free, one can use stitching by rotating the camera around the axis that passes through the lens entrance pupil and other than achieving much wider angles, use swings between shots as to achieve an impressive result for perspective.

For completely yaw free operation to be achieved, the lens entrance pupil must be positioned at exactly at the center of  the circle of which the tilt arc is part of the perimeter and then the swing movements mechanism center to be on the same axis as the entrance pupil of the lens and the center of the tilt arc... Therefore, for the M2 or other camera to be yaw free, it is not a matter of camera design, but more a matter of lens positioning on the frame.

Ideally, for a camera to be of completely yaw free operation with any lens attached on it, the front and rear frames should be adjustable back and forth on the standard so that the user positions the frame so that its entrance pupil is at the correct position despite the lens used (of course the same applies for the center of the image area on the rear frame) and additionally, if the camera has shift mechanisms on the same standard, up-down shift mechanism should be UNDERNEATH the tilt mechanism and side shifts should be underneath the swing mechanism... otherwise combination of these movements should be avoided because they'll destroy yaw free operation.

Excellent explanation. Now I've got a razor sharp conception of how it all works. Does the Cambo Ultima work well?

From this topic: http://forum.luminous-landscape.com/index.php?topic=37015
Copy this:

2. Yaw-Free

There has always been many misinterpretations of what means "yaw-free". Many false statements have been made here, since this design has been introduced by Sinar with the Sinar p.
"Yaw-free" means that the VERTICAL Swing axis remains in the tilted plane when you are using your HORIZONTAL tilt axis to adjust your sharpness plane, nothing more but nothing less. It is a mechanical construction property.
In this respect, the Sinar p/p2/p3 remains a "yaw-free" camera, with the tilt/swing axis being inside the capture frame or not.

Best regards,
Thierry

Totally agree with Thierry, (the bold font done by me). Thierry no longer participate in this forum but his answer fits perfectly in this topic.

Gentlemen, i strongly recommend you read this: http://www.sinar.ch/en/category/know-how-en/yaw-free/
and books: "The Large Format, Handbook of the SINAR System" and "Photo Know How", of authors Carl Koch, Jost J. Marchesi, C. Marchesi.
Although these books relate solely to Sinar system of the film era, they remain the best reference for understanding the operation of the view camera, even today, in our digital age. The fundamental function remains the same.

[landscapephoto]

So basically what Sinar says is that "yaw free" means that the vertical and horizontal rotation axis of the front standard cross on the focus rack, while Theodoros says that it means that the vertical and horizontal rotation axis of the front standard are placed at the entrance pupil of the lens, right?

[Theodoros]

 
Focusing point of a lens is always its entrance pupil position.

EDIT: The lens plane, is a plane vertical to the lens axis and the entrance pupil is the point where the two cross.

[landscapephoto]

Focusing point of a lens is always its entrance pupil position.

EDIT: The lens plane, is a plane vertical to the lens axis and the entrance pupil is the point where the two cross.

Definition of the entrance pupil (wikipedia).

[Theodoros]

http://www.sinar.ch/en/yaw-free/ 

[Theodoros]

Scheimpflug's law does state that three planes (the image area's plane, the subject's plane and the lens plane) should cross in a line... but it also assumes (which is never stated) that the projection radius of the cone projected in the image area should remain constant as it was if the subject was focused without any movements applied and thus, only a part of it in focus...

In other words it means that your camera is both yaw free and distortionless only if you can focus it without movements, then apply the movements you want (shifts & up downs included) and never have to refocus it... Otherwise (if you have to refocus it) there will be distortions (on all directions) involved in the image captured...

The more the focus will need corrections, the more the (distortion) error... The closer the subject's plane, the more evident the (distortion) error...

[landscapephoto]

Scheimpflug's law does state that three planes (the image area's plane, the subject's plane and the lens plane) should cross in a line... but it also assumes (which is never stated) that the projection radius of the cone projected in the image area should remain constant as it was if the subject was focused without any movements applied and thus, only a part of it in focus...

No, it does not assume any of that. Scheimpflug uses Gauss' approximation of thin lenses.

[Theodoros]

https://en.wikipedia.org/wiki/Scheimpflug_principle 

 Notice the following in the second paragraph...

"When the lens and image planes are not parallel, adjusting focus[1] rotates the PoF (plane of focus) rather than displacing it along the lens axis. The axis of rotation is the intersection of the lens’s front focal plane and a plane through the center of the lens parallel to the image plane, as shown in Figure 3.

[landscapephoto]

https://en.wikipedia.org/wiki/Scheimpflug_principle 

 Notice the following in the second paragraph...

When the lens and image planes are not parallel, adjusting focus[1] rotates the PoF (plane of focus) rather than displacing it along the lens axis. The axis of rotation is the intersection of the lens’s front focal plane and a plane through the center of the lens parallel to the image plane, as shown in Figure 3.

I put in bold the part corresponding to the assumption of "thin lenses" in the citation above. If one does not make that particular assumption, one would define cardinal points and not a "center of the lens".

You are using approximations of geometrical optics in a case where one cannot make these approximations. In my experience, this is often the case for photographers, because their education just presents the simple optical formulas they may need without specifying that these classical formulas are approximations. The approximations are valid in standard cases (e.g. when the subject is far away, so that the thickness of the lens is negligible compared to the distance to the subject), so they are usually sufficient for photographers. OTOH, there are photographic cases for which the approximations are no more valid (e.g. macro photography) and the "classical" formulas then do not work.

[Theodoros]

 The interception of two planes where one is the lens's front focal plane and the other a plane through the center of the lens, is always a line that passes through the lens entrance pupil...  It is clearly shown on all figures.

EDIT: Additionally, on figures 5 & 7 one can see what the result would be if the lens plane and the lens's front focal plane are the same plane (which then means that all rotations are made through an axis that passes through the entrance pupil)... in this case not only the system Satisfies Scheimpflug's law, but it stays distortionless too... (which in cases where the subject is close is precious...).