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Thread: Importance of back movements

  1. #11
    Drew Wiley
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    Re: Importance of back movements

    Hmm, my back doesn't move as easily as it used to.... but if you're referring to my camera's back, I often make use of that when tilting the camera downward. If only front tilt is used to handle plane of focus distribution, it requires a far larger image circle than using or combining the rear tilt option, or requires a smaller f-stop, or counting on the less than ideal nether realm of the image circle rather than the center. Learning to use back tilt is therefore valuable. And of course, geometric perspective is affected differently, so that in itself becomes another correction tool, relative to front vs rear tilts or combination thereof. Swing is analogous. But Rise vs fall - either way, no difference. My 8x10 flatbed doesn't even have rear swing of height adjustment; but I like it that way for its overall simplicity and rigidity. My Sinar monorail does it all.

  2. #12

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    Re: Importance of back movements

    Horseman TooTed "focus plane rise" as one of their view camera movement features back in the day..
    https://www.kenko-pi.co.jp/horseman/e/L45.html

    On a Sinar Norma, simply move the front or rear frame as needed to re-frame the GG image and done. Similar for Sinar F or P.


    As for lens image circle, typical 4x5 table top lens focal length would be ~ 210mm, a modern Plasmat would have a larger image circle than most cameras have the ability to move their front / rear standards at table top image ratios.

    Don't forget the bellows factor compensation or under exposure assured.


    Bernice

  3. #13

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    Re: Importance of back movements

    For me, the only important rear movements are swing, rise and shift.

    Swing is useful for optimizing horizontal Scheimpflug. This can be convenient for architecture, for example.

    True shift happens on the rear, not the front. Though, front shift is often used and can be managed to simulate rear shift.

    Rear rise is useful, for example, in case there's insufficient front fall. Rear rise can also be used to effect pointing the camera down. (See Drew's comment.)

    As for tilt, front tilt is essential, and it's the only tilt that's needed. Keeping verticals parallel is a matter of keeping the back vertical, and without rear vertical tilt, it's thereby a matter of keeping the rail horizontal.
    Last edited by neil poulsen; 10-Jun-2021 at 04:03.

  4. #14

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    Re: Importance of back movements

    I look at all these movements in a different way.

    Two things really matter in image management: 1. The position of the back in relation to the subject and 2. The relative positions of lensboard to film plane.

    The position of the back determines the projection, i.e., how the 3D subject will be rendered on the film plane including relative sizes of near and far objects and rendering of parallel lines.

    The positions of the lens and film planes to each other dictate where the plane of sharp focus gets positioned relative to the film plane.

    So, you can change the position of the plane of sharp focus with either front or back movements, but if you use the back movements, you also end up changing the perspective rendering of the image. (Sidebar: Please, don't take me to task for this usage of the word, "perspective." It's a perfectly good and alternate use of the word and I haven't found a better one to use in cases like this.)

    If one wants parallel lines in a scene rendered parallel on the film, the film plane must be parallel to the plane those parallel lines lie in. That's true for either horizontal or vertical parallels (although we have a lot more tolerance for converging horizontal lines than vertical ones for some reason).

    So, why would we want to use back tilt: One reason would be to bring the back parallel to vertical lines in the subject after the camera had been pointed downward. Another would be to make a foreground object appear larger in relation to other objects in the scene than it would with the camera in "zero" position, say a near boulder that you wanted to dominate the frame, etc. And, one could always use back tilt to get the plane of sharp focus better onto the film, realizing, of course, that the image rendering will be changed accordingly and taking that into account.

    One reason back tilt gets used instead of front tilt is in cases where the required front tilt would move the image circle projected by the lens so much as to cause vignetting (a particular problem with lenses with limited coverage and front tilt/swing). Then, using a combination of front and rear tilt or rear tilt alone will prevent the vignetting (but change the image rendering, which may not be objectionable in many cases).

    Another reason for back tilt: some cameras don't have front tilts or swings. If you need them, you can imitate them by pointing the camera and then tilting/swinging the back. All that really matters is 1. the position of the back in relation to the subject and 2. the relative positions of lensboard to film plane.

    There are several "hacks" like this: pointing the camera up and then tilting the standards plumb again to get effective front rise, etc. All that really matters...

    Best,

    Doremus

  5. #15
    Land-Scapegrace Heroique's Avatar
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    Re: Importance of back movements

    Quote Originally Posted by Doremus Scudder View Post
    …if you use the back movements, you also end up changing the perspective rendering of the image.

    (Sidebar: Please, don't take me to task for this usage of the word, "perspective." It's a perfectly good and alternate use of the word and I haven't found a better one to use in cases like this.)
    Hey, wait a minute, I agree, but I’m still going to take you to task. Didn’t we clear this up long, long ago, in an eternal, never-ending thread about perspective? That is, “Geometric perspective” for certain back movements, “Viewpoint perspective” for certain front movements. A nice post Doremus. ;^)

  6. #16
    Alan Klein's Avatar
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    Re: Importance of back movements

    My Chamonix 45H-1 has asymmetrical tilt but only when you use the back standard. That makes tilting "easier" but it does add distortion but not noticeable on landscape pictures.

  7. #17

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    Re: Importance of back movements

    Quote Originally Posted by Heroique View Post
    Hey, wait a minute, I agree, but I’m still going to take you to task. Didn’t we clear this up long, long ago, in an eternal, never-ending thread about perspective? That is, “Geometric perspective” for certain back movements, “Viewpoint perspective” for certain front movements. A nice post Doremus. ;^)
    Thanks!

    As far as "perspective" is concerned: it's cleared up for me, but there are those who haven't seen that older thread and those who participated in the thread that never really accepted the consensus; just deflecting the "corrections" before they come.

    Best,

    Doremus

  8. #18
    Alan Klein's Avatar
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    Re: Importance of back movements

    So what's the best way to make the walls of buildings plumb (vertical)? I also have a asymmetric tilt using the back standard. How would that work with this issue?

  9. #19

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    Re: Importance of back movements

    Quote Originally Posted by Alan Klein View Post
    So what's the best way to make the walls of buildings plumb (vertical)? I also have a asymmetric tilt using the back standard. How would that work with this issue?
    You make the back plumb to the walls of the buiding

  10. #20
    Mark Sawyer's Avatar
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    Re: Importance of back movements

    Quote Originally Posted by Bob Salomon View Post
    You make the back plumb to the walls of the building
    ...and then use front rise to center the frame on the building. No other movements are necessary.
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

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