How to Focus a View Camera Part II

[tgtaylor]

According to Euclidean Geometry two unique points determine a line and three a unique plane in space. Suppose you have a high-end view camera such as the Toyo Robos, GX, or Sinar P, PII that provide for both base and/or axial tilts and wanted to set-up a unique plane of focus in space. How would you proceed? Would you determine the line of focus using base tilt, axial tilt, a combination thereof, or something else? What about those points falling in the foreground or background of the plane that you also want to be in focus?

Thomas

[Bob Salomon]

Assymetrical axis cameras like the Linhof Master GTL, Sinar P & P2 and the Toyo Robos all have 2 tilt points and one swing point on each standard. These cameras are yaw free as one of the tilt points on each standard is below the swing point.

A camera like the Linhof Kardan Bi has both a single tilt point and a single swing point on each standard. It is not yaw free.

Unless you rotate the camera body 45° around the monorail. When you do this the swing point becomes the tilt point and the tilt point now becomes the swing point. As the tilt point is now below the swing point the camera becomes yaw free.

The Sinar system had a single line on the gg that the subject was placed on. If the subject didn’t lie on that plane a front shift, or rear shift, was required to place the subject on that plane.

The Linhof system had a continuously variable that the subject would lie on thus setting up frequently in 1 or more fewer steps then a Sinar.

[Mark Sawyer]

According to Euclidean Geometry two unique points determine a line and three a unique plane in space. Suppose you have a high-end view camera such as the Toyo Robos, GX, or Sinar P, PII that provide for both base and/or axial tilts and wanted to set-up a unique plane of focus in space. How would you proceed?

You'd need to get into Cartesian Geometry.

[tgtaylor]

Mark - I'm afraid that your knowledge of analytic geometry is far less than your knowledge of photography which appears to be on par with the typical high school photography novice. At one time - maybe 10 years back - there were people on the internet that could answer that type of question, but not any longer!

Thomas

[Mark Sawyer]

Mark - I'm afraid that your knowledge of analytic geometry is far less than your knowledge of photography which appears to be on par with the typical high school photography novice...

I think quite a few typical high school photography novices are feeling quite offended...

[Graham Patterson]

[...] What about those points falling in the foreground or background of the plane that you also want to be in focus?

Thomas

Stop down as needed. A Plane is a Plane - stopping down is the only way to get a third dimension.

Since I don't have the luxury of axial controls on most of my cameras, it has to be iterative - initial focus, movements for primary adjustment, focus review, movements for secondary adjustment, focus review and depth of field calculation.

Then pack up, because the light has gone 8-(

[Jim Noel]

Mark - I'm afraid that your knowledge of analytic geometry is far less than your knowledge of photography which appears to be on par with the typical high school photography novice. At one time - maybe 10 years back - there were people on the internet that could answer that type of question, but not any longer!

Thomas

There are still some of us around who can answer the question, but most, like me prefer to not spend the time doing so. There are several treatises on the web dealing with the subject fully. look for Merklinger on Focusing the View camera.

[tgtaylor]

Nope - I read thru the various posts on the subject and everyone seems to be fuzzy about it. I'm probably the only person alive that can give a crystal clear answer to it but I'll keep it to myself.

Thomas

[Jerry Bodine]

Nope - I read thru the various posts on the subject and everyone seems to be fuzzy about it. I'm probably the only person alive that can give a crystal clear answer to it but I'll keep it to myself.

If that's true, then why did you start this thread, sir?

[Doremus Scudder]

Three points do indeed define a plane. When using swings and tilts together to bring an oblique plane into sharp focus, it is helpful to choose three key points to focus on and use the movements to bring all three into simultaneous sharp focus. Visualizing where the PoSF should lie and choosing your focus points is critical here.

Keep in mind that the plane of sharp focus is where the camera is in focus and that objects on either side of the plane can be brought into acceptably sharp focus with adequate depth of field. The distance on either side of the PoSF that is rendered acceptably sharp varies not only with the aperture size (smaller = more DoF) but also the distance from the camera (nearer = less DoF).

How much you need to stop down for a given subject to render it acceptably sharp in a final print depends on the focus spread between near and far in the scene (i.e., how deep the scene is), the degree of enlargement, and your own personal standards of sharpness. Diffraction at very small apertures limits sharpness for subjects with extreme focus spread/degree of enlargement. Finding the optimum compromise here is what "focusing a view camera" is all about for me.

In truth, however, we're talking about several different things: Focusing on a chosen point or points by racking the bellows in and out and using whatever magnifying device you like (inaccuracies are easy here...) Placing the PoSF using movements, which is more or less complicated depending on the subject being photographed and, finally, choosing an optimum aperture to render the desired amount of sharpness (or out-of-focus) in the scene. It seems this latter provokes most of the discussion. I like the near-far split method described in the article about choosing the optimum aperture on the LF home page.

I don't really think we need a lot of higher geometry to do the focusing job adequately...

Best,

Doremus