Are view cameras "yaw free" with retrofocus lenses?

[Theodoros]

Shouldn't the entrace pupil's center being in constant position for this to happen?

[torger]

It's not 100% yaw free, but as retrofocus comes with wide angle you generally employ very low amounts of tilt/swing so you don't really notice the small error that's there. At least that's my experience, although I have more experience with symmetrical lenses. My widest sits on a recessed board though which also introduces a similar error and I haven't experienced any practical issues from that.

If we look at the older view cameras the tilt could be located down at the rail which caused a large distance change with changed tilt, so it's that we compare with. Putting the rotation around the center of the lens board does not remove the issue 100% but reduces it so much that it's no longer relevant for normal use.

With the widest my workflow is generally to set the tilt first, and then focus. When using ground glass it's typically near-impossible to look into the edge and check tilt-related sharpness. Instead you lookup tilt from a table, and then focus for the far point which generally is close to the center and perfectly viewable. With live view you could do otherwise though, and maybe you could detect a yaw error there.

[Theodoros]

It's not 100% yaw free, but as retrofocus comes with wide angle you generally employ very low amounts of tilt/swing so you don't really notice the small error that's there. At least that's my experience, although I have more experience with symmetrical lenses. My widest sits on a recessed board though which also introduces a similar error and I haven't experienced any practical issues from that.

If we look at the older view cameras the tilt could be located down at the rail which caused a large distance change with changed tilt, so it's that we compare with. Putting the rotation around the center of the lens board does not remove the issue 100% but reduces it so much that it's no longer relevant for normal use.

With the widest my workflow is generally to set the tilt first, and then focus. When using ground glass it's typically near-impossible to look into the edge and check tilt-related sharpness. Instead you lookup tilt from a table, and then focus for the far point which generally is close to the center and perfectly viewable. With live view you could do otherwise though, and maybe you could detect a yaw error there.

It's not always a small problem, with narrower image circles for instance, it can lead to an uneven frame as tilting the front standard causes shifting of the rear standard (actual, not mechanical)... and then, is the rear standard yaw free? For this to happen, all different image areas should be at the same position and the "yaw free" calibrated for the center of the light sensitive area... but if one uses a sliding back or if one uses a mirrorless instead, there is no correction for this with any (existing) view camera... Recessed boards (as you point out) do extend the problem to even symmetric lenses...

[Bart_van_der_Wolf]

Shouldn't the exit pupil's center being in constant position for this to happen?

Hi,

The entrance pupil should be kept in the same position (rotate around its center) to avoid Yaw or a change in perspective. Lens design doesn't matter then, only the entrance pupil.

Rotating the plane of the Rear standard will change the projection perspective on a flat plane, the plane becomes an intersection with a cone of light, and the image circle will lose its round shape and becomes elliptical (or even parabolic) if not cut of by lens barrel limitations when also shifted. But image magnification also changes with the perspective projection changes.

Cheers,
Bart

[Theodoros]

Hi,

The entrance pupil.........

Well, obviously its the entrance pupil (what we are used to call "nodal point" which is also not correct) that should be kept constant... I've edited the O/P to correct the (unintentional) mistake... Thanks for noticing Bart... 

[Theodoros]

Rotating the plane of the Rear standard will change the projection perspective on a flat plane, the plane becomes an intersection with a cone of light, and the image circle will lose its round shape and becomes elliptical (or even parabolic) if not cut of by lens barrel limitations when also shifted. But image magnification also changes with the perspective projection changes.

Cheers,
Bart

I think that it is best if one takes care that the rear standard of his camera behaves as being yaw free (because its far easier to adjust - with some personal work and skills) and then perform tilts and swings using the rear standard rather than the front one (which is the usual process)... Unless of course if one checks that yaw free is valid with his front standard and certain lenses...
It does surprise me though that there is no camera in the market that has the lens mounting plate user adjustable so that the user can adjust it accordingly for each lens he uses as to ensure that he can have distortion free images when he tilts or swings using the front standard... Surely distortion is limited  enough as not to be visible at long focusing distances, but for architectural work (especially for interiors) it can be of major importance...