scheimpflug -> little help?

Discussion in 'Large Format Cameras and Accessories' started by game, Nov 9, 2007.

  1. game

    game Member

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    hi there,

    I have been restling the scheimpflug principle for a few occasions now, and I do get the idea, but cannot seem to find any links that show some 'real-life' examples instead of the mathematical drawings.

    What I am trying to do is photographing a room, and have the chair that in the front of the room and the table that's in the back to be sharp both. That should be possible, right?!

    but if I focus on the chair, tilt my lens untill the table is sharp than the chair is not any longer.

    what's is going on? Don't need full explaination, I am willing to think for myself, but some help would be appreciated!!

    thanks a lot, kind regards game
     
  2. Jordan.K

    Jordan.K Subscriber

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    game,
    I think you may want to tilt less and stop the lens down more. Too much tilt will only result in selective focus issues as far as I know. When you stop the lens down you most likely won't be able to tell that both are in focus through the ground glass because it will be too dark to see. Focus on one of the object and then stop down to about f45, this may achieve the results you are looking to get.
     
  3. MurrayMinchin

    MurrayMinchin Membership Council Council

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    Lens board vertical - plane of focus vertical. Tilt the lens board - the plane of focus becomes slanted away from the camera.

    Tilting the lens works great for flat subjects like table tops or flat desert areas, but stick something tall like a tree or chair in the frame and it goes out of focus. When you tilt the lens and use a small aperture, think of the plane of focus as a wedge, with the pointy end at the camera...this means your chair might still be out of focus no matter how small an aperture you use.

    Murray
     
  4. David H. Bebbington

    David H. Bebbington Inactive

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    What kind of camera are you using? If it has an on-axis tilt, it will maintain focus (at the center of the screen) when you tilt the front, otherwise you will need to re-focus. What lens are you using? With any tilt movement, there is a point where you run out of lens coverage, with a wide-angle lens you reach this point fairly soon. However, assuming the chair is not too close (say, not closer than 1.5 meters), it should be possible to get deep focus from the front to the back.

    Regards,

    David
     
  5. Soeren

    Soeren Member

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    I played around with my Sinar yesterday with some extreme tilt on front and back. I managed to get our kitchen faucet, some flowers and part of the roof next door only slightly above the faucet in focus. I was a bit surpriced how much it took.
    I tilt the front at the same time I do the focus back and forth, back and forth, until I find the right angle and point of focus.
    Somebody may know the easier way so Im all ears/eyes
    Kind regards
    Søren
     
  6. Lukas Werth

    Lukas Werth Member

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    In my early days of view camera use, I remember I fumbled around until the picture on the ground glass looked alright, often using too much tilt, and without a real clou of how exactly the plane of sharp focus is placed, and what can be and cannot be done by stopping down. Then I got Harold Merklinger's "Focussing the view camera". Not an easy read for me, but I found it extremely helpful. Since then I have a much more systematic grasp on focussing, know what to expect, and focuss in much shorter time.
    He explains what he calls the "hinge rule", a crucial elaboration on the scheimpflug rule.
     
  7. Ole

    Ole Moderator Staff Member Moderator

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    Harold Merklinger's book is available for download from HERE. That, and the rest of the "stuff" on that address is recommended reading.

    Next, remember that you can only get one plane in focus, but you can put that just about wherever you want.

    And then it depends on where the tilt axis is compared to the rear(?) node of the lens you are using. Unless the tilt axis passes directly through the node, you will get focus shift and will need to apply tilt, refocus, tilt, refocus repeatedly until you get it right. Even cameras with axis tilt may need this "fine tuning" of focus, since the lens node may not be exactly on the axis. A very few cameras have adjustable offsets, but even if mine is one of them I rarely bother to "pre-tune" the tilt axis.
     
  8. c6h6o3

    c6h6o3 Member

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    Remembering that all you can do is shift where the plane is critical focus is, do this:

    1) Determine two points (nearest and farthest) with which you want your plane of critical focus to intersect.

    2) Focus on the far point. Lock down the focus.

    3) Tilt the standard (front one for less distortion, rear one if you want near objects to loom larger) until the near point is in focus. Don't worry about the far one going out of focus (yet). Lock down the standard.

    4) Refocus on the far point. Lock it down.

    5) Repeat steps 2 through 4 until both points of your plane are in focus with the lens wide open.

    6) Stop down the lens until the depth of field brings everything around the plane of critical focus into acceptable focus.

    Doing it this way allows you to quickly get everything in focus without having to imagine the Schiempflug line. A good mnemonic for remembering which way to tilt a standard is this: "the front faces, the back backs away". In other words, in your case you would tilt the front standard toward the plane you want (forward) to "face it" and tilt the rear one toward yourself to "back it away". I never think about where the Schiempflug line is anymore.

    Remember, this won't get you any more depth of field. It just changes the position of the line around which the depth of field wraps. Hope this helps.
     
  9. panastasia

    panastasia Member

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    Start with: "focus on the near, tilt towards the far" - refocus if necessary and correct linear distortion w/rear standard) - then stop down. That's about as simple as I can say it for starting out. Some people do it the other way around, so I don't believe there's any golden rule.
     
  10. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    It's hard to give advice on this scene without seeing what it looks like. Without using the camera, do you see all the things that you want in focus falling in approximately the same plane? If not, then tilting may not be the right approach.

    Generally, if you have a relatively tall vertical object in the foreground (relative to whatever is in the background), this is when it's better to stop down for DOF rather than using tilt to manipulate the plane of focus. If the plane of focus is passing through the tall vertical object, then it won't be in focus.
     
  11. Allen Friday

    Allen Friday Member

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    Yesterday, I posted two images in the critique gallery for which I used the scheimpflug technique. They are Scenic By-way #1 and #2.

    I recommend that you start with a flat suface like a table top or road and practice getting it sharp and then move on to three demensional objects. With front tilt, you lay the plane of focus down toward the horizontal, and you have to use a smaller f-stop to bring three-d objects into focus. Try getting the table top in focus first.

    Allen
     
  12. game

    game Member

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    Thanks guys, this is what I wanted!!!

    great, kind regards
     
  13. epatsellis

    epatsellis Member

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    Soeren,
    Without being critical, might I ask if you're familiar with how the Sinar tilt/DOF calculator system works? On most (all?) Sinar cameras, there is a tilt calculator built in, which gets you there quickly, as well as a reasonably accurate (though I tend to stop down an additonal stop) DOF calculator.
     
  14. walter23

    walter23 Member

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    The way I usually deal with scheimpflug in practice is as follows. When you have your first object (or point) in focus, the relative position on the ground glass of a second object that you want in focus, combined with the direction you have to focus to get it in focus ("out" or "in", if focusing with the front standard) tells you what kind of movement to apply.

    For this example, remember that the ground glass is an upside down and backwards representation, but when I say "top" I mean the actual top of your ground glass and when I say "right" I mean the actual right side of your glass - not the position of those objects in the real world beyond the camera.

    So, for example, on the ground glass you've got an object on the left that is in focus, and an object on the right that is not in focus. To get the object on the right focused, you have to focus the front standard out (increase extension) because in this example that object is closer to you. You can use that information to say "okay, move the right side of the front lensboard "out"" (because the right-most object required a focus adjustment "out"). This is just a mental shortcut that happens to fit how the movements work out (that "right most" object on your GG is actually to the left in reality, and since it is closer to you moving the right side of the lens board "out" is the correct movement).

    If I have an object on the bottom that is in focus, and an object on the top that is out of focus but that can be brought into focus by focusing the front standard "back" (decreasing extension), then I tilt the top of the lens board back. Note that the inverse relationship works just as well; in the same scenario I could say that to get the bottom object in focus I have to focus "out", and therefore I have to tilt the bottom of the lens board out. This is the same movement as tilting the front back (because that puts the bottom of the lens board relatively "out").

    In this way you can focus on one important object in your focus plane, switch your attention to the other object and adjust focus for it (while noting which way you focus), and then use this principle to apply a slight tilt or swing. Test it again and see which way you need to move, and with a few iterations you can get it perfect.

    This isn't really the technically correct way to look at the scheimpflug principle optically, but it's a shortcut that always works.
     
    Last edited by a moderator: Nov 11, 2007
  15. Bruce Osgood

    Bruce Osgood Membership Council Council

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    What I know of the Scheimpflug Principle is that when you work hard enough to focus everything by eye and it works, you have proven the Scheimpflug Principle.
     
  16. CPorter

    CPorter Member

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    Something that I have learned since my entry into LF and dealing with lens tilt is that the plane of focus tilts more than the tilt given to the lens and so it can be easy to apply too much tilt. I have been quite frustrated at times by providing too much tilt and then having to go back and forth with it more than it seems I should.
     
  17. epatsellis

    epatsellis Member

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    Chuck,

    Exactly right, in theory, it tilts at double the rate of the lens tilt. Ole has made mention of Merklinger's work, you should read it, quite fascinating stuff. It can help you get your head around some of the more arcane and not so obvious parts.


    erie
     
  18. Soeren

    Soeren Member

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    Nothing wrong with being critical. No I don't know how it works or what it is or how to get it :smile: But since Im a beginner Im open for suggestions and good advice.
    Kind regards
    Søren
     
  19. Steve Smith

    Steve Smith Subscriber

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    When researching Shheimpflug, also look up 'The Hinge rule'.

    The two need to be applied together: http://www.trenholm.org/hmmerk/HMbooks4.html

    The Sheimpflug rule on its own only gives one point which the plane of focus passes through making its angle ambiguous. the Hinge rule gives a second point. A straight line through both of these points is the focus plane.


    Steve.