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Thread: how to calculate swing

  1. #1

    how to calculate swing

    To all,
    I am relatively new to large format and have been using a method described in this forum to calculate the amount of tilt required which I really like for field use: angle of tilt= (60)X(focus spread) divided by (the distance on the ground glass between the two points used for the distance spread).

    Can this same rule be used to calculate swing or is there another equally simple math way to calculate the amount of swing needed for a particular scene?

    Also, are tilt and swing completely indepenent of each other or is there some type of mutual interaction between the two.

    I apologize for my ignorance in this area but I am trying to read several books on this subject which are slowly becoming increasingly less opaque. Others understanding of these issue with more practical experience than myself would be greatly appreciated since reading books is primarily theory at this point for me.

    Thank you in advance,

    Dan Dumitru

  2. #2

    Join Date
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    how to calculate swing

    I am one of those forget the math and learn to look at the gg kind of guys. In my experience teaching workshops I find that beginners frequently tilt/swing too much. Sometimes it is just a skooch (kind of like a hair) and that the answer is almost always less than 10 degrees and often less than 5 degrees..I also recommend one of the gg brighteners tomake the image easer to see. This will help a lot.

    steve smmons
    www.viewcamera.com

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    how to calculate swing

    Dan: At the risk of also sounding rather non-technical, I will also add that having a ground glass, which shows you the effect of movements, has always been a simple technique which works quite well. For landscapes, the amount of tilt is usually a very small amount, contrary to what you might think from looking at manufacturer's ads, which prefer to show view cameras twisted into non-photographic pretzel positions. Learn about tilts and swings by watching what they do to the image on the ground glass. Find the amount which is the best compromise between near and far, stop down and check the ground glass to make sure the parts you want are in focus, then take the picture.

  4. #4

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    how to calculate swing

    Use the ground glass! In an average landscape scenario taken with a 90mm lens you would be looking at a tilt/swing of about 5 degrees. Remember a swing is basically a tilt on its side!

  5. #5

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    how to calculate swing

    Edward Weston didn't need no stinkin' tilts or swings.
    Wilhelm (Sarasota)

  6. #6
    Moderator Ralph Barker's Avatar
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    how to calculate swing

    I just think of swing as tilt, resting on its side. All of the same methods apply. The only complication I've encountered in combining them is working within the limits of the coverage of the lens, and compromises with focus. I decide which plane is more important, and do that (tilt or swing) first.

  7. #7

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    how to calculate swing

    I will risk actually trying to answer your question instead of telling you to do something entirely different. We all differ in what we find easy and what we find hard.

    Yes. The rule, usually called Wheeler's Rule, also works for swings. But you would apply it somewhat differently. When you do a pure tilt, you usually envision a near point in the foregound (at the top of the gg) and a far point in the background (lower on the gg). You then measure the vertical distance between them and use that in your formula. If you use it for a swing, you would choose a near point on the right of the gg, a far point to its left, or vice versa, and measure the horizontal distance between them to use in the formula. Whether you use right-left or left-right would depend on which way you were swinging. Generally you swing so that the lensboard moves on one side away from the image of the near point and on the other side towards the image of the far point. Drawing some Scheimpflug diagrams should make this clear.

    I've found what is for me a simpler form of Wheeler's Rule, which doesn't rely on an angle which may sometimes be hard to measure. I'll describe it for a tilt. Take that same ratio of distances you use but instead of multiplying it by 60, do the following. Measure the vertical distance from the top of the lens board to the axis on which the lens tilts forward. Multiply the ratio by that distance, and then tilt so as to move the top of the board the resulting distance forward.

    To answer your second question requires some background. A view camera generally allows you to tilt the lensboard about a horizontal axis and to swing it about a vertical axis. If the lensboard were entirely free to move, you could in principle rotate it about any axis at all, but because of the physical restraints of the mechanism, you can't do that. Fortunately, you can obtain such a rotation about some oblique axis by an appropriate combination of a tilt and a swing. If you had such an oblique axis in mind which you could describe quantitatively, then it would be possible to calculate what tilt and swing angle to use. But you rarely have such information available in the field. It would be more straight forward to try to visualize the desired exact plane of focus in the subject and the line where it intersects the (extended) film plane. Scheimpflug's Rule says the lens plane has to intersect that, so you would experiment with tilts and swings until you saw the (extended) plane of the lens board intersecting that Scheimpflug line.

    As to the advice about relying purely on the gg, I think this is easier for experienced view camera users than it is for beginners. There are in fact a relatively few common situations where you might be using a tilt or less often a swing. So by experience, you get a good feeling for how much to tilt or swing and you let what you see on the gg help you fine tune the action. Rules like Wheeler's Rule are useful when you are beginning because they get you pretty close to where you should be, and then you can fine tune the result on the gg. As you get more experience, you will find you use it less and less. but it is good to keep it in mind for tricky situations.

    I've covered some of this in my essay at www.math.northwestern.edu/~len/photos/pages/dof_essay.pdf.

  8. #8

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    how to calculate swing

    I suppose the mathematical calculation of swing will follow the same path as tilt, since it's the same movement turned 90 degrees.

    I have to go along with the majority, however: use the groundglass! You'll not run into many (if any) situations that demand more movement than can be delivered by most cameras. Those times when the camera doesn't have anough swing, chances are the lens you're using will run out of image circle anyway.

    It's easy to get wrapped up the elegant mathematics that describe LF photography, but that's a trap. The true beauty of large format photography is found under the darkcloth, for the time you spend there is profoundly yours alone.

  9. #9

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    how to calculate swing

    The pocket sized Rodenstock DOF/Scheipflug calculator computes tilt/swing on any format from 35 to 8 x10 with a level or inclined rail. No math required.

  10. #10

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    how to calculate swing

    Forget the calculations. Its a waste of time and energy. You need to be looking through the ground glass. If you are trusting the calcs to get it right, you are going to be disapointed sooner or later. Some will no doubt dispute this, but the human eye is more accurate than the calculations. The Scheimpflug stuff is merely a way of explaining things on paper. Totally unecessary for actual use.

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