Explaining Yaw free, distortionless & Yaw free/distortionless operation of a camera..

[Bruce Watson]

All I know is, if I level and plumb the film plane I can then use front tilt, swing, and shifts to make a more-or-less artistic image. But if I do this with some subjects, like buildings, the resulting print looks somehow unnatural. All those lines perfectly straight and parallel. In those cases, I use a little back tilt to create some keystoning, to make the image look "natural". Which it's not. But that's photography for ya.

I'm just sayin' that you can argue these things to death, but that the ground glass doesn't lie. What you see is what's important. I leave the math to the people designing cameras and lenses, and of course to the people posting in this thread.

[ic-racer]

If one's camera Yaws or not when making certain movements, one still needs to set up the correct focal plane. A camera that shows Yaw when doing certain movements only requires secondary movements to obtain the correct focal plane. My daughter can do it.

[Peter Lewin]

Perhaps I am missing the point, unless it is that all of us using field cameras should go out and buy yaw-free Sinar P2s or another of the relatively small number of yaw-free cameras out there. To put it differently, is there something those of us with cameras that are not yaw-free should be doing?

[Theodoros]

Perhaps I am missing the point, unless it is that all of us using field cameras should go out and buy yaw-free Sinar P2s or another of the relatively small number of yaw-free cameras out there. To put it differently, is there something those of us with cameras that are not yaw-free should be doing?

Of course there is... (that's why this discussion is for)...

1. Make sure that your lens entrance pupil is positioned exactly at the center of the circle of which the tilt arc is part off... This will ensure that when tilting or swinging, the cone projected on the image plane will be one that its "top" is always the center of the same sphere and thus you'll have a circle projected... not an "egg shape"...
2. (after you make sure 1 above is satisfied) use your side shift's mechanism, or your up-down one, only if it is positioned bellow the respective swing & tilt ones. This means that if you need to side shift, don't do it with your front standard unless the side shift is bellow the swing mechanism and don't up-down shift (do it with your rear standard) unless your front standard's respective mechanism is below the tilt one...
This is because if you tilt or swing and your shift mechanisms are above the tilt/swing ones, the lens entrance pupil will not be centered anymore to the circle of which the tilt arc is part of the radius anymore and your swing axis won't be passing anymore from the axis around which the lens rotates... (in return the lens entrance pupil will move like if it is on a perimeter around it - think of a door that opens around an axis)...
3. Make sure that your image area's plane on the rear standard, is positioned on the same plane that intersects the tilt arc exactly at the middle of it (the "0" position), if it isn't, only use side and up down shifts on the rear standard and never tilts or swings... Other wise (in combination with 1&2 before) your image plane won't "receive" your lens cone projection as being a circle anymore, but at an angle...

Ideal situation is if you do position your lens entrance pupil in the center of the circle of which the tilt arc is part of the radius (and which the swing axis penetrates anyway), then do the same for the center of your light sensitive area and you have chosen a camera that has all its side and up down shift below the respective swing and tilt mechanisms on both standards... You can then do whatever you like with both standards and enjoy another level with your photography...

[Taija71A]

This Thread is definitely beginning to remind me of a 'Comedic Play'.
--
However, I do not recognize any of the 'Main' Characters from Shakespeare.
Where are Don Pedro, Dogberry, Leonato, Borachio or Benedick?

Also and 'More intriguingly' within these conversations...
We still are not laughing -- At any of the Jokes.

Why is that?
Perhaps, it really is... "Much Ado About Nothing".
--
The First Law of the View Camera (The Scheimpflug Principle)... Is now 'OLD NEWS'.
How about we talk about the Second Law (The Hinge Rule) of the View Camera -- Instead?

View Camera Focus and Depth of Field -- Part I.
http://www.trenholm.org/hmmerk/VCFaDOF1.pdf
_______

[Pere Casals]

I do not understand that:

No way! Distortions induced in an image captured as stereo (three axis perpendicular to each other), there is no way that can be corrected on a (two axis) plane...

My reasoning is next:

> We have an initial circular "circle of image" (say distortion free) projected on a "large" negative. (no movements)

> For simplicity let's think that diafragm is very closed and recorded field is inside DOF.

> Also let's think that negative is way larger than image circle.


If we do any tilt-swing with the camera standards we'll "linearly" distort this projected circle into an ellipse, that will be recorded in the negative. Any tilt-swing will always result in a projected ellipse. True... Does not?


> Then always we can find and tilt-swing inclination of the paper under te enlarger than will restore a circle on the paper, from the ellipse that was recorded in the negative... thus obtaining the same image (focus plane apart) that it would have been obtained without any tilt-swing done with the camera.


This is the reasoning I was thinking it was correct... I'm not sure of it... In any case, what is it incorrect in this reasoning??

[aluncrockford]

I do not understand that:





My reasoning is next:

> We have an initial circular "circle of image" (say distortion free) projected on a "large" negative. (no movements)

> For simplicity let's think that diafragm is very closed and recorded field is inside DOF.

> Also let's think that negative is way larger than image circle.


If we do any tilt-swing with the camera standards we'll "linearly" distort this projected circle into an ellipse, that will be recorded in the negative. Any tilt-swing will always result in a projected ellipse. True... Does not?


> Then always we can find and tilt-swing inclination of the paper under te enlarger than will restore a circle on the paper, from the ellipse that was recorded in the negative... thus obtaining the same image (focus plane apart) that it would have been obtained without any tilt-swing done with the camera.


This is the reasoning I was thinking it was correct... I'm not sure of it... In any case, what is it incorrect in this reasoning??

[aluncrockford]

I am curious as to who, of all the posters on this subject has actually used a 10x8 camera using all the movements needed to produce an outcome that satisfies a client . As someone who has worked as a photographer using 10x8 for advertising clients for the last thirty years I have to say that everything I have read here is not unlike a learn how to swim instruction book, might I suggest that if you are interested in using large format cameras with or without yaw free, then the best thing to do is actually take some pictures, personally I use a P2 in the studio and Deardorff on location both options are perfect , swapping them around would be less so

[Pere Casals]

then the best thing to do is actually take some pictures,

Yes... it's very, very important to practice... but knowing the theory (Scheimpflug, Hinge...) also helps

And the other thing that also helps is to see photographs from skilled people, and to understand how they creatively used movements, and the particularities of the lenses, the film, the process and the postprocess.

A lot to learn and to practice...

[Doremus Scudder]

Doremus - I think distortion in your example of non-parallel lens and film is really a magnification change across the image. ...

We're all probably in agreement about the same effects, it's just a difference in semantics.

I think we're just using terminology from different fields. With geometric projections as in mapmaking, a change of relative size of the projected image compared to the real subject is termed distortion. In a Mercator projection, for example, Greenland appears much bigger in relation to, say, Spain than it really is. The change in magnification due to the type of projection is termed distortion. Using swings or tilts on view camera results in a similar thing (the conic section being now an ellipse) and is therefore, "distorted." Similarly, a circular conic projection will have a different magnification at the edge of the film plane than at the center; it's a function of distance from the lens exit pupil. The distortion of objects at the edge of the image with very short focal-length lenses is a good example of this, but it exists in any lens.

To be clear, I'm not talking about lens aberrations here, just the inherent distortion in geometric projections. This distortion is always there in a conic projection and is greater the greater the difference in distance from the lens exit pupil. We have to keep in mind that we LF photographers are usually only using a part of the projected image, so the optical center of the image is often displaced from center on the film. This is simply cropping.

So, yaw-free or not, or whatever, it's really only the position of the lens plane and exit pupil relative to the film plane that determines any change in relative magnification of the image and, therefore, "distortion."

@aluncrockford: I don't shoot 8x10, but 4x5. Nevertheless, I use movements often and confidently and visualize my images in terms of planes of sharp focus and parallels. I think I've got a pretty good handle on the practical aspects of applying movements, using any of base, axis or asymmetric tilts/swings and with yaw and without. I'm trying to point out that there's really no such thing as distortion-free when using a camera of any kind.

Best,

Doremus