Tilt / swing lens placement question...

[Sim2]

Hallo all,
If this is in the incorrect forum, do please relocate it!

Question: If using a normal lens for tilt or swing, mounted on a panel, does it matter if the lens mount is on the tilt/swing axis or should the center of the lens be on the axis? (with the lens mount recessed from the axis plane).

Hope this is understandable – I will endeavor to clarify queries, if needed!

Thanks in advance.

 

[AgX]

It practically does not matter.
The image will slide off the the film format anyway, unless the lens has enough coverage.
Locating the lens center off the the til/swing axis will only enlarge the problem.

However axis location at the rear standard does matter with tilt/swing.

 

[Sim2]

Thanks for your reply.
I am making an assumption that a lens will have some excess coverage on at the film plane.
Thinking about how to elaborate the question is proving tricky but... there would be no (intended) rise/fall or shift of the lens. I think there could be 2 centers of the lens.
The diameter of the lens or any lens elements, will have a central point i.e. where the radius is located – in my example, this will not alter by rise/fall or shift.
Looking at the lens from the side, i.e. a cross section, in lens (simple) diagrams there is a point where the rays of light entering the lens converge before widening to exit the lens. I shall call this Center 2! There must be a technical term for this but *brain fade*.
If the normal lens has its mount located at the axis of the swing/ tilt, the Center 2 would be in front of the swing/tilt axis.
If the Center 2 manages to be located at the axis of the swing/tilt, the normal lens mount will be behind the swing/tilt axis.
Do these two options give different results? Would they both work?

*thinking of doing a drawing...*

 

[E. von Hoegh]

I assume you're talking about view cameras. First - your lens must have a sharp image circle significantly larger than the diagonal of the film you are using. Second - front tilts & swings control plane of focus, so on or off axis, it doesn't matter so much. However, rear movements (film plane) control both plane of focus AND perspective; so on axis movements at the rear are very convenient. Front movements, tilt/swing, place more demand on lens coverage than rear tilt/swing.

 

[Sim2]

Thanks for your replies, I'm not sure that I am able to explain my query properly. My theoretical thoughts would get an answer if I can try it out for real!
*looks for toolbox*
Thank you for considering my query.

 

[jim10219]

To answer your original question, it mostly matters for ease of use. If the physical axis of tilt or swing is not located at the optical axis of the lens, then it may make altering those adjustments a bit less intuitive, and cause you to have to refocus the lens every time you do. However, in the end, you can probably still come away with the same shot. Now, another problem is if location of the physical axis is off from the optical center axis, then you run the risk of running out of image circle quicker to project onto the film plane. This is assuming you don't have rise/fall/shift controls as well to compensate for the lenses movements away from physical center.

 

[AgX]

It will matter under certain exact circumstances. If you got a viewcamera and predetermin lens settings by setting the groundglass first.
So if your camera has rear axis exactly within the ground glass plain and you focus on a subject exactly on that axis and then swing the ground glass until a second subject is in focus too, read the tilt/swing, set to neutral the groundglass and tilt/swing the lens according to that reading, you need axis at the lens to be located in optical center.