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Thread: View Camera Focusing and the Scheimpflug Principle

  1. #1

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    View Camera Focusing and the Scheimpflug Principle

    Okay, I actually did a search on this and couldn't find a satisfactory answer to this question. - have also consulted my books and it is unclear:

    When focussing any view camera, and applying the Scheimpflug law, why doesn't the entire scene, if done correctly, come into perfect, sharp focus on the GG? Even with many, complex movements? As in, you have correctly set the plane of focus to correspond with the important areas of the subject, which happens to NOT be parallel to the film plane. I've always been told and it seems to be this way in practice too, that you first focus on the far, make your movements for the near, then refocus until you have "split the difference" between the near and far. Neither will be in perfect focus, then stop down to bring everything relatively sharp for the shot. It seems to me tha if movements are properly applied, everything should be sharp already, even at a fairly large aperture.

    Which brings me to part two of this question: The Scheimpflug principle states that when the subject plane of [desired] focus, the lens plane (front standard) and the film plane (rear standard) are all allowed to form converging lines, then everything on the subject plane will be in focus. Or something to that effect.

    Here's a somewhat simplified example of what I'm asking here: It seems to me that if, for instance, you wanted to focus on a vertical wall, with the camera slightly pointed upward, and you left the front standard at zero and applied a little back tilt, you'd then have your converging lines, the "SP" would be satisfied and the wall would be able to brought into perfectly sharp focus at, say, f5.6. The building might be a little distorted in this example, but should still have wall in sharp focus, right?

    Why can't I seem to be ale to achieve this in practice? It seems to me that ANY TIME I have a little front std front tilt and rear standard back tilt, I should be satisfying the SP and be able to bring that part of scene into razor sharp focus?

    Frankly, I don't use that many movements in the type of photography I do. I.e., point camera at flat wall of building, level and zero everything, and trip shutter. Like I would with any non view camera. I've been discouraged from working with movements much, because of my frustrating lack of understanding on this focus issue.

    Thanks ahead for your collective wisdom and comments!

    Phil aka "Cletus"

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    Re: View Camera Focusing and the Scheimpflug Principle

    Maybe this too complicated a question? Is this like asking "how do I use my camera"?

    Maybe to simplify -

    If movements are used correctly, shouldn't the entire plane of focus be tack sharp on the GG without stopping down to f90?

    If there is front-forward tilt and rear-back tilt, isn't the requirement for the SP focus typically met?

  3. #3

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    Re: View Camera Focusing and the Scheimpflug Principle

    Quote Originally Posted by Cletus View Post
    Maybe this too complicated a question? Is this like asking "how do I use my camera"?

    Maybe to simplify -

    If movements are used correctly, shouldn't the entire plane of focus be tack sharp on the GG without stopping down to f90?

    If there is front-forward tilt and rear-back tilt, isn't the requirement for the SP focus typically met?
    If you knew precisely where the plane of focus should be, and you moved the front and rear standards the correct amount to make the planes intersect, the plane of focus would fall on the GG perfectly, the first time, every time. Since none of these conditions obtain, you go back and forth, checking the GG with a loupe, until you get it where you want it. Simply tilting the front and back is not correct - the three planes must intersect.

    If you are having to stop down to f;90, you aren't getting the Scheimpflug movements right. Put a map on the table top, set up the camera above and to one side of the table. You will find that you can have the entire frame filled with a part of the map, at about lifesize on the GG, and the map will be perfectly sharp at maximum aperture, the map being a 2 dimensional object. If your subject is 3 dimensional, you still have to stop down the get the parts outside the plane (which by definition is 2 dimensional) of focus.
    Last edited by E. von Hoegh; 7-Aug-2012 at 08:23.
    One man's Mede is another man's Persian.

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    Re: View Camera Focusing and the Scheimpflug Principle

    Quote Originally Posted by E. von Hoegh View Post
    If you knew precisely where the plane of focus should be, and you moved the front and rear standards the correct amount to make the planes intersect, the plane of focus would fall on the GG perfectly, the first time, every time. Since none of these conditions obtain, you go back and forth, checking the GG with a loupe, until you get it where you want it. Simply tilting the front and back is not correct - the planes must intersect.

    If you are having to stop down to f;90, you aren't getting the Scheimpflug movements right. Put a map on the table top, set up the camera above and to one side of the table. You will find that you can have the entire frame filled with a part of the map, at about lifesize on the GG, and the map will be perfectly sharp at maximum aperture, the map being a 2 dimensional object. If your subject is 3 dimensional, you still have to stop down the get the parts outside the plane (which by definition is 2 dimensional) of focus.
    In your example, move to the side of the camere, about 10 ft away. Draw a line through the rear standard where the film plane is; draw a line through the front standard where the lens board is. Project these who lines downward until they meet.

    If the point where these two lines meet isn't part of the wall then you'll never get your subject in focus (this presumes a non-telephoto lens for reasons I can't be bothered to go into).

    If you want the wall in focus with the camera pointed slightly up, the lens board plane, the film plane and the wall should all converge somewhere some distance below ground level.

    Tim
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    Re: View Camera Focusing and the Scheimpflug Principle

    One man's Mede is another man's Persian.

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    Re: View Camera Focusing and the Scheimpflug Principle

    The Scheimpflug Principle is not a theory, its a useful tool. Sometimes I can get lost and confused under the dark cloth when I don't seem to be able to find the plane I'm looking for, but it always is grounding to move away and look to the side of the camera to see if the 3 planes converge in a reasonable way. Like many things, practice seems to work wonders.
    John Youngblood
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    Re: View Camera Focusing and the Scheimpflug Principle

    There are cameras that are designed to make it easy, but they depend on a subject that has an obvious desired focus plane. Few scenes have all the subjects you want sharp in a single plane. So you have to make a decision about what to include in the focus plane, and then adjust the movements to achieve that. Then, use depth of field to bring the remainder into acceptable sharpness. The depth of field will be a wedge-shaped zone that is narrower the closer the focus plane is to the camera, so the tilts must be more precisely adjusted for near objectives where depth of field is less.

    For landscapes, where you are mostly trying to run the focus plane along the ground, you can focus on the near object and then tilt (with base tilts) outward to bring in the distant object. But you will still probably have to readjust several times as you zero in on getting the focus plane exactly where you want it. It is possible to get it right.

    In the picture below, I applied a small amount of downward tilt and a bit of swing. I picked three points on the trunk of the tree to be in precise focus, and they are in precise focus (three points always fall on one plane). I had to fiddle with the tiny adjustments quite a bit to get them just right. I was trying to avoid too small an f-stop because there was a breeze and those leaves were just dancing. But I wanted all those major tree branches to be sharp. The main subject was pretty close to the camera and thus depth of field was narrow even at a small f-stop.


    Japanese Maple in Autumn

    I positioned the camera so that the leaves at the left edge were in the focus plane.

    I bet I spent over half an hour fiddling with the tilt and swing adjustments, using a loupe on the ground glass to check the settings, until my main three points were all perfectly focused. The reward for that effort was an f/16 aperture, and the reward for that was a 1-second shutter speed using Velvia 50. Had I used f/32, I'd have had to find a 4-second period when those leaves were still. Not happening that day.

    The lens on this was a 121mm f/8 Super Angulon on 6x12.

    In summary: The only time you have to compromise on tilts and swings is if you have subject material you want to be in focus that is not all on the same plane. Then, you have to find a plane that gets close (with "close" having a more demanding definition in the near field) and then stop down to obtain the necessary depth of field. But if you can identify a flat focus plane, then keep adjusting until it's in good focus even wide open.

    Rick "the compromise is in deciding where to put the focus plane, not the movements needed to make that focus plane sharply focused" Denney

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    Re: View Camera Focusing and the Scheimpflug Principle

    There are three planes involved in focusing a view camera. Initially all three are parallel:
    one through the film, one through the lensboard, and one through the subject.

    The SP enables you to change the plane of focus, that initially went vertically through the subject,
    to intersect the other two planes.

    Simple description (leaving the back vertical):
    Tilting the lensboard forward moves the BOTTOM of the plane of focus toward the camera.

    Tilting the lensboard relative to the back DEFINES the plane of focus, which intersects the other two planes at their common line.

    For this to work in practice you must consider depth of field (DoF), which varies with the distance from the camera.
    Viewed from the side (with from tilt), the region of proper focus looks like a wedge with its apex at the camera,
    getting larger as distance increases.

    The f-stop controls DoF, but now it's relative to the tilted plane of focus, no longer front-to-back.

    - Leigh
    If you believe you can, or you believe you can't... you're right.

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    Re: View Camera Focusing and the Scheimpflug Principle

    To just do a roughly close adjustment without precises measurements of intersections and such, I look at what I am going to photograph be it table top or landscape in envision how I want the plane of focus to lay and then from experience I know that the plane of focus moves about twice as much as the plane of the lens board. It is a rough estimate but gets you close enough to start fine tuning with the loupe.

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    Re: View Camera Focusing and the Scheimpflug Principle

    Thank you for the practical advice -

    E., I will definitely try the "Map Trick" as an exercise to help me illustrate your point. I do understand there must be three basic planes that must intersect - that being the Film, Lens and Subject planes.

    In my example of the camera pointed up at the wall, this was my assumption:

    Since the camera is not level (and the wall is), the wall forms the flat, 2D subject plane, with a line extending straight down toward the center of the earth. Tilting the front standard back slightly, so the top of the front standard is further from the wall than the bottom of the front standard - remember the camera is not level, it's pointed up at an angle - forms the lens plane, whose line will eventually converge with the subject plane line. Finally, adding some back tilt to the rear standard, the film plane line will now converge with the other two and come to a "point" somewhere, probably meeting somewhere below ground level, ultimately.

    Doesn't this still satisfy the SP requirements? Isn't the actual location of the node of the three converging lines irrelevant? This was the crux of my question I guess. It seems to me, when I've tried to experiment with this, and even though the three planes seem to eventually meet, I am still unable to get my 2D subject plane into sharp focus. There could be other factors affecting this as well and looking at the camera from the side to determine the approximate location of the convergence makes a lot of sense to me. It never occurred to me to do that.

    rdenny - Nice photo of the tree and nice way to illustrate your example, BTW.

    Anyway - Collectively, you have all confirmed my suspicion that a 2D plane, regardless of it's orientation, should be able to be brought into sharp focus using movements correctly. That whole issue with me is based on some MIS information I received some time ago, when just learning how to manipulate a view camera and it's always bothered me that it didn't sound correct. Also, I do understand that a 3D plane, as opposed to 2D one, will need a certain amount of DoF to compensate for what can't be brought into tack sharp focus.

    I plan to refer back to this thread while doing some test shots on the table tomorrow!

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