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Thread: Importance of back movements

  1. #41
    Alan Klein's Avatar
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    Re: Importance of back movements

    Doremus. I'm still confused how you get the wall's lines plumb and parallel yet do the tilt for maximum DOF.

  2. #42

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    Re: Importance of back movements

    Quote Originally Posted by Alan Klein View Post
    Doremus. I'm still confused how you get the wall's lines plumb and parallel yet do the tilt for maximum DOF.
    Alan,

    Don't confuse tilt/swing for purposes of optimizing the position of the plane of sharp focus with positioning the back for rendering parallel vertical or horizontal lines in the scene parallel on the film.

    To reiterate: the position of the back in relation to the parallel lines in the subject determines how they will be rendered on the film.

    If the back is positioned plumb, then it should be parallel to the vertical axis of a building (assuming the building is plumb) and the vertical lines in the building will be rendered parallel on the film.

    Keeping horizontals parallel is just the same as keeping verticals plumb and parallel, just 90░ different: For horizontal parallels, the back needs to be parallel to the horizontal axis of the wall (or whatever) you want to be rendered "square" on the film.

    It works the same both vertically and horizontally. That's really all there is to it.

    Often, we position the back plumb so vertical lines are rendered parallel, but don't worry about the convergence of horizontal lines in a wall, etc. That's just fine. However, if you want parallel horizontal lines on a wall to be parallel on the film (for whatever reason), then the camera back has to be parallel to the horizontal axis of the wall.

    Note here that using front tilt or swing after you lock down the camera back in your desired position does not affect the image rendering. It will move the plane of sharp focus around in the scene. This may or may not be desirable.

    If you use back tilt or swing at any point, you'll affect the image rendering. Maybe you do this on purpose, e.g., swing the back to get more convergence of horizontal lines, etc. Just don't do it accidentally after you've got the back in the position you want it in relation to the subject both vertically and horizontally.

    Some examples:

    Imagine a tall building that we want the verticals to not keystone on. We set up the camera with the back plumb, i.e., parallel to the verticals axis of the building. Then we use front rise to frame the image. For many of these type of shots, we keep the lens standard in "zero" position too, i.e., parallel to the back and the fašade vertically. So it's just a matter of setting up the camera plumb, framing with front rise and making the exposure.

    But in scenes where there is a lot of foreground and an important foreground object that needs to be sharp, then tilting the front a bit (not the back; it's already where we want it: plumb) can sometimes position the plane of sharp focus more optimally, and keep us from having to stop down into diffraction degradation too far.

    Let's say we have a horizontal brick wall, and we want all the vertical and horizontal lines to be parallel on the film. Then we set up with the camera back plumb (that takes care of the vertical axis) and also parallel horizontally to the wall. This latter requires that you pan the camera and watch the ground glass until you find the position where all horizontal lines are parallel (a gridded ground glass helps here). Then you lock down the back and don't touch it.

    If we don't have our desired framing after you've moved the back into a position horizontally parallel with the wall, we can a) move the camera to get the framing we want, or, b) we can use shift, framing the image horizontally just like we did using front rise to frame the tall building in the first example.

    Everything on the wall will be in focus as long as the film plane and lens plane are parallel to the wall both horizontally and vertically. However, what if we want to intentionally render the sides of the wall out of focus and have just a stripe of sharp focus in the middle? Then we'd use front swing to move the plane of sharp focus around to get the effect we want.


    Final example:

    Set up to make an image of a similar brick wall, but this time we can't position the camera directly in front of where we'd like it to be; we have to set up off to one side.

    Okay, we set up with the back plumb (taking care of the verticals) and point the camera at the wall at an oblique angle. At this point, the parallel lines in the wall will converge slightly. So we have to make a decision regarding back position and the rendering of those horizontal parallel lines (forget focus for now). We have lots of choices: We could leave the image as it is, but maybe that's not what we want.

    So, one thing we could do is emphasize the convergence. This would mean swinging the back away from parallel to the wall until we got the degree of convergence we wanted. Of course, then the entire wall is not going to be in the plane of sharp focus. So, we lock down the back and use front swing (in the opposite direction as we swung the back) to position the plane of sharp focus onto the wall (Scheimpflug principle here.) Done and make the shot. Notice that you can't use your asymmetrical back movements here to position the plane of sharp focus since the back is positioned to get the composition you want first and any further back movement would destroy that.

    However, maybe we don't want more convergence in the wall; maybe we want those horizontals to be parallel on the film instead. What to do?
    Well, we could simply pan the camera so that the back was parallel with the wall horizontally and then use shift to frame the image, as described above...

    == OR ==

    We could leave the camera pointed where it already is and simply swing the back parallel to the wall. Of course, then the entire wall is not going to be in the plane of sharp focus. So, we lock down the back and use front swing to position the plane of sharp focus. This time, we'll need to bring the lens plane parallel with the film plane, so the swing will be in the same direction as the back swing.

    And, our final camera configuration will be, as far as the relation of lens standard and camera back, the same as if we'd used shift. This is how we get effective shift on field cameras that don't have shift movements: point the camera at the scene and then swing both the back and the lens parallel to the wall.

    And remember, once we get the camera back positioned where we want it for image perspective, we can still move the plane of sharp focus around with front tilts and swings. So, if in any of the above scenarios, a bit of tilt or swing helps to position the plane of sharp focus more optimally, then we should use it.

    Hope this helps,

    Doremus

  3. #43
    Alan Klein's Avatar
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    Re: Importance of back movements

    Thanks
    I have to spend some time experimenting with different scenes and movements.

  4. #44

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    Re: Importance of back movements

    YES!

    Spend some reading time with this chapter lifted from the Linhof view camera book. Explains view camera movements and lots more:
    https://www.largeformatphotography.i...ong-amp-Linhof


    Bernice


    Quote Originally Posted by Alan Klein View Post
    Thanks
    I have to spend some time experimenting with different scenes and movements.

  5. #45
    Alan Klein's Avatar
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    Re: Importance of back movements

    Quote Originally Posted by Alan Klein View Post
    Here's a digital capture of a shot I did today with my 4x5, My Chamonix has asymmetrical tilts allowed with the rear standard. Your comments appreciated.


    Camera standards all started at default positions and leveled. Plumb, etc. My camera was too high so the first thing I did was to lower the front standard to get the wheel into the picture.

    My camera has asymmetrical using the rear standard. Normally the read standard is just to tilt. In this case I did the following:

    So first I focused on the axis line (green) where the X is in the white window. I then swung the rear standard so the right side was further away and the left side closer to help with the angle of the wall receding on the left. I played with the focus and angle a couple of times until it seemed it was all in focus. Then I tilted the front forward just a bit to help with the focus of the wheels where the x is on the blue line.
    Here's the actual Provia 100 4x5 taken.
    Attached Thumbnails Attached Thumbnails 1600-007.jpg  

  6. #46
    Alan Klein's Avatar
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    Re: Importance of back movements

    Here's an Ektachrome converted to BW.


    Dey Farm Wheels
    by Alan Klein, on Flickr

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