focusing confusion

[nwilkins]

If you read the title of this post it will probably come as no surprise that I am a newcomer to LF. I have been doing some reading and I thought I was pretty much understanding what happened with tilts/swings.

But then I read the following (from Howard Bond's checklist):

"a tilted plane of focus moves parallel to itself when the focus knob is turned, just as it does with a rigid camera. Choose two targets that are in a plane that is parallel to the one you want to make sharp. After these target images have been made sharp with the help of a swing or tilt, turn the focus knob to move the focus to the desired plane. "

I thought that when you focused the camera it rotated the angle of the plane of focus along the hinge line? Or am I getting that wrong?

Thanks in advance,

Nick

[Heroique]

Hi Nick,

I'll try to offer a very, very simple answer, but you might also consult AA's The Camera for a great overview about LF focusing + very helpful illustrations.

Once you visualize your best plane of focus, you can "get there" (that is, move your camera's plane of focus to coincide with this "best" plane of focus) by using, say, front swings/tilts and/or the focusing knob. Using front swings/tilts moves the plane differently than the focusing knob. You normally hear the words "hinge lines" and "rotation" for the former, and "parallel movement" for the latter. It might take both to arrive at the best plane of focus, but a neutral camera (no movements, just focusing with the knob) can get you there, too.

Using DOF to satisfy your focus needs is a related (and very important) focusing issue.

[ic-racer]

am I getting that wrong?

You are getting that wrong . Keep reading and practicing.

[Bob Salomon]

Read pages 10 to 12.

http://linhof.com/wp-content/uploads...rge_format.pdf

[nwilkins]

You are getting that wrong . Keep reading and practicing.

so changing the distance between the film and lens does not change the angle of the plane of focus? Really?

[nwilkins]

Read pages 10 to 12.

http://linhof.com/wp-content/uploads...rge_format.pdf

thanks Bob but I didn't see anything about the effect that focusing has on the plane of focus in that pdf

[nwilkins]

okay I am realizing I didn't make myself very clear. so I'll try and explain again. I'm sorry for the confusion. new post coming in a minute here

[nwilkins]

Okay here goes:

I understand what happens to the plane of focus when I tilt the lens. It is now no longer parallel to the film plane. It now extends away from the camera at some angle, and is the shape of a cone.

Everything I have tried out on the ground glass (and read about) seems to indicate to me that changing the distance between the film and lens (let's call this x) changes the angle of the plane of focus. so at a given x the plane of focus might be parallel to the ground, but at a different value for x the plane of focus might start at the ground but move higher as it extends away from the camera.

So I thought that this was the rotation of the plane of focus (around what the Merklinger website calls the hinge line).

Is this correct? ic-racer says no but if it isn't correct then I am more confused than ever.

[Heroique]

…the shape of a cone.

You might try "wedge," not "cone."

I am more confused than ever.

Do you have a local library?

Excellent books on technique with awesome illustrations:
1) The Camera by Ansel Adams
2) View Camera Technique by Leslie Stroebel
3) Using the View Camera by Steve Simmons

You might also use the site's search function. Below are some really cool terms to learn about, from our very own armchair and practitioning experts:

Geometric plane
Film plane
Lens plane
Plane of focus
Best plane of focus
Front movements, back movements
Scheimpflug rule (or principle)
Geometric perspective
Viewpoint perspective
Depth of field (DOF)

[Bob Salomon]

Try it this way.
The depth of field, when shooting at normal distances, runs 1/3rd toward the camera - from the point focused on - and 2/3rds away from that point.

You use your tilts/swings to capture the plane of focus desired. You ensure the apparently sharp area desired by focusing 1/3rd into the desired area and stop down so the entire desired surrounding area is also sharp. Remembering that most lenses are diffraction limited to f22 so you usually do not want to exceed that stop.

Scheimpflug/DOF calculators like Rodenstock's help you to easily compute the proper angles and apertures to capture these shots easily and in expensively by measuring the difference between the near and far points desired when you focus on those points. You might want to look this pocket sized double sided calculator up. It works for all formats from 35mm to 810.