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Thread: Scheimpflug in Practice

  1. #1

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    Scheimpflug in Practice

    I'm pretty much brand new to all of this. I've read The Camera, and a bunch of stuff on the Internet about camera movements, so in theory I have some idea how all this works. In practice though, this is the first thing I've really tried shooting with a view camera, as kind of a test, and I'm curious how more experienced folks would approach it.

    My goal was to get the entire thing in focus, so conceptually I knew that I needed to swing the lens to the right to shift the plane of focus. My problem was that when it came to actually getting the right tilt to produce the right plane--especially combined with the fact that I needed the camera angled down to get it in view, as rise/fall weren't sufficient from that height--I found myself just kind of floundering around guessing at settings and never quite getting it right. Ultimately I did get the top part of the band a little more in focus than a normal camera would have allowed, but I totally lost the bottom.

    How would you approach this more methodically? I've been thinking it might help to try to visualize the intersection of the subject plane and the image plane and aim the lens plane at that, but even then that seems like it would be very imprecise. Do you actually take measurements of the angles involved in this kind of situation, or is there a more intuitive way to do it?

  2. #2
    jp's Avatar
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    Re: Scheimpflug in Practice

    My intuitive non mathematical way is that at infinity or long distances, the bellows draw = focal length and bellows will be at their minimum. Things get reversed as they go through the lens. Things low in a scene end up high inside the camera. Sky ends up at the bottom of the camera. Simple empirical pinhole / camera obscura stuff so far. Now add a lens that focuses.

    If the top of the lens is tilted down a bit like scheimpflug, there is a greater distance within the camera at the top so the focus distance will be shorter for things at the bottom of the scene. With some front standard tilt you can have top and bottom of the camera focus on different distances because the top and bottom of the lens are differnent distances from the film. Draw a line between those two distances in the scene and you have your plane of focus.

    Here's one https://flic.kr/p/DGE5NY I did indoors with my 8x10 and Kodak 305.. I have the foreground hose in focus and the corner of the couch which should have included my daughter's face, but the lens does not have a flat field as it was not made for 8x10 and/or she may have moved a little bit as it was not a kid friendly exposure time.

    In practice, the amount of tilt adjustment is much less than sales pictures for view cameras that look contorted. I reversed a front standard on my speed graphic and it's has very modest tilt and that's plenty for outdoor scheimpflug. My wooden B&J 8x10 seems like just a few small degrees of adjustment makes noticeable changes in the plane of focus. No measurement. Just learn to operate the adjustments of the front standard while viewing the ground glass, which is more about camera familiarity and inspector gadget arms than measurement and academics. With a precise SINAR camera you might learn certain lenses at certain distances need a certain adjustment and it might save you time to record angles, but it's not necessary and probably rarely practiced.

  3. #3

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    Re: Scheimpflug in Practice

    Quote Originally Posted by bieber View Post
    I'm pretty much brand new to all of this. I've read The Camera, and a bunch of stuff on the Internet about camera movements, so in theory I have some idea how all this works. In practice though, this is the first thing I've really tried shooting with a view camera, as kind of a test, and I'm curious how more experienced folks would approach it.

    My goal was to get the entire thing in focus, so conceptually I knew that I needed to swing the lens to the right to shift the plane of focus. My problem was that when it came to actually getting the right tilt to produce the right plane--especially combined with the fact that I needed the camera angled down to get it in view, as rise/fall weren't sufficient from that height--I found myself just kind of floundering around guessing at settings and never quite getting it right. Ultimately I did get the top part of the band a little more in focus than a normal camera would have allowed, but I totally lost the bottom.

    How would you approach this more methodically? I've been thinking it might help to try to visualize the intersection of the subject plane and the image plane and aim the lens plane at that, but even then that seems like it would be very imprecise. Do you actually take measurements of the angles involved in this kind of situation, or is there a more intuitive way to do it?
    You can do it with math but (even coming from a physics background) I don't think you'd ever get around to taking the picture.

    The plane of focus moves the same way as the lens board but a little more extremely than the lens board does. Tilt the lens board forwards, plane of focus tilts forwards. Swing the lens board to the left, plane of focus swings to the left. Generally, the plane of focus changes angle faster than does the lensboard, so you get a little bit more than you expect.

    Of course, on most camera+lens combos, moving the lens also throws the focus out of whack. So you have to refocus, which throws the movements out of whack...

    The process I'd use to shoot your watch, with the intent to lay the plane of focus down parallel to the table to get all the watch in focus, is this:

    1) Set everything up.
    2) Focus on whatever's dead-center in the ground glass.
    3) Confirm that the two opposite ends of the watch strap are more unsharp than I'm willing deal with.
    4) Think "OK, I need to tip the plane of focus forwards to get it to lay down flat on the table. That means I need to tip the lens board forwards"
    5) Tip the lensboard forwards MUCH LESS than I think I'm going to need to. If I think I'm going to need 45* of tilt, I start with maybe 10-15*
    6) Everything is now out of focus
    7) Focus on whatever's in the dead-center of the ground glass.
    8) Confirm that the two opposite ends of the watch strap are more unsharp than I'm willing deal with but that the region of acceptable sharpness in the middle got a little bigger (since the plane of focus is now slightly tipped).
    9) Think "OK, that helped, so I'm moving in the right direction but I need a little more"
    10) Tip the lensboard forwards MUCH LESS than I think I'm going to need to.
    11) Everything is now out of focus
    12) Focus on whatever's dead-center in the ground glass.

    etc.


    At first, tiny movements of the lens board and a dozen cycles through the "which way, small tilt, refocus, check it" loop is the fastest way to get where you need to go. It's really easy to think you need to move the lens more than you actually do and overshoot. You end up frustrated and wondering why it doesn't work the way the book says. With some practice, it's pretty easy to get down to 2-3 cycles the adjust-focus-check loop to get it dialed in.

  4. #4
    Vaughn's Avatar
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    Re: Scheimpflug in Practice

    I would not have used any swing...it does not seem to be needed in that example...just front (and/or back) tilt.

    Once I think I have the plane of focus where I want it, and if I still have unfocused areas with the lens wide open, I close down the lens slowly watching the out of focus areas. If both near and far areas come into focus as the same time (same aperature), then I know I am focused properly. If the front comes into focus first, then I move the focus back until I can get far and near to come into focus at the same aperature.
    "Landscapes exist in the material world yet soar in the realms of the spirit..." Tsung Ping, 5th Century China

  5. #5

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    Re: Scheimpflug in Practice

    Thanks for the tips, everyone. Another interesting thing this brings up is, in a scenario like this where the object is both tilted horizontally at an angle and pretty flat vertically, how do you decide between using tilt or swing? Do you just go for whichever one is closest to the natural focal plane? Or is tilt inherently easier to work with than swing?

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    Re: Scheimpflug in Practice

    Quote Originally Posted by bieber View Post
    Thanks for the tips, everyone. Another interesting thing this brings up is, in a scenario like this where the object is both tilted horizontally at an angle and pretty flat vertically, how do you decide between using tilt or swing? Do you just go for whichever one is closest to the natural focal plane? Or is tilt inherently easier to work with than swing?
    Tilt and swing are identical. Roll the camera 90* and one becomes the other without anything changing.

    If the camera is plumb in roll (level left-to-right) and the table top is level and the camera is just pitched down to see the watch, you'd need pure tilt. If you've got both pitch and roll in the camera position, or if the table top is not at right angles to reality, then you'll need some combination of swing and tilt together to get the plane of focus to match the plane of the table top.

    Now, that assumes that your goal is to lay the plane of focus down on the table top. I think that's how most people would approach the problem.



    However, with the specific cast of the watch, there's a second, less obvious, way to tackle it. You can also swing the plane of focus until it lies parallel to the strap. If you do that, you can get the whole watch in focus by using the swing movement to get the opposite tips of the strap in focus and then stopping down until the Depth of Field is fat enough to keep the entirety of the watch case sharp. The potential downside (or potential awesomeness) to doing this is that the plane of focus would slice through the table. This means that, while the watch would be sharp, the table down and to the left (relative to your picture) of the watch and up and to the right of he watch would be out of focus. With the all-white table you used, this won't be apparent. However, if the watch were resting on something with texture, pattern, or print, you'd see this weird cockeyed slice of sharpness the watch would be lying in. This would be either horrible or awesome.

  7. #7
    Vaughn's Avatar
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    Re: Scheimpflug in Practice

    Mentally place a flat plane over the surface you are photographing -- in your example, it is parallel to the same plane the watch is laying on. I do not see this plane as titled right/left, even though the object goes right to left in the scene.

    If the watch was on a textured surface, using swing would throw some of that texture out of focus.
    "Landscapes exist in the material world yet soar in the realms of the spirit..." Tsung Ping, 5th Century China

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    Mark Sawyer's Avatar
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    Re: Scheimpflug in Practice

    Scheimpflug works in theory, but it seldom works in practice. There's always something sticking up or out where it shouldn't be. God made the world that way just to torment large format photographers.

    It's perhaps the best example of Yogi Berra's old observation, "In theory, practice and theory are the same thing. In practice, they're not."
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  9. #9

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    Re: Scheimpflug in Practice

    Hi!

    You can have a look at the two diagrams below

    https://www.flickr.com/photos/43175600@N00/6245674051/

    https://www.flickr.com/photos/43175600@N00/6246188810/

    An important thing to keep in mind is that for landscape photography, tilt angles required for a proper Scheimpflug setting are small.
    For example, with a 150 mm lens, located at 5 feet above ground [1.5 m], tilting by 6° brings ground level to sharp focus, this is a small angle!
    So, do not start with a tilting angle of 30° like in this legendary advertising picture, you'll have really hard times to find the proper focus ;-)

    However, tilt angles can be high with long focal lengths, for taking pictures of objects located close to the camera, like for pictures of objects for catalogues in the good old days whre the LF camera was the proper tool for this kind of commercial photography.


    My goal was to get the entire thing in focus

    Another thing to remember is that tilting + Scheimpflug changes the shape of the portion of object space considered as sharp to a wedge, so objects outside the wedge will not be seen sharp.

    For example, for this kind of "tunnel-style" picture, again taken from an advertising image (for a local well-known French product), tilting the lens or the film plane will be useless to achieve "infinite depth of field".

    You can find a nice Scheimpflug simulator by Tim Parkin here

    http://static.timparkin.co.uk/static/focus/

    See this discussion with examples on the British LF forum.
    http://www.lf-photo.org.uk/forum/vie...php?f=3&t=2859

    Yes, simulation will be useless in the field, but at least a simulation at home can tell you what is possible, or not, to achieve in the field, in the real, non-mathematical world.

  10. #10

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    Re: Scheimpflug in Practice

    Quote Originally Posted by Vaughn View Post
    Mentally place a flat plane over the surface you are photographing...
    Vaughn's point here is right on. It's really important to mentally determine the where you want the plane of sharp focus to be; only then can you really decide what movements you need.

    So, if the plane you want to focus on is not parallel to the back, but displaced top-to-bottom (e.g., like a near/far landscape of flat ground), you need tilts. If the plane you want to focus on is displaced right-to-left (e.g., a wall is close on one side and stretches into the distance), you need swings. If the displacement is oblique, you'll need both swing and tilt.

    Once I've determined where I want the plane of sharp focus to be, I choose focus points: top and bottom of the ground glass for scenario 1, right and left of the ground glass for scenario 2 and both top/bottom and right/left for scenario 3.

    Before applying tilts or swings remember the old adage: "The back backs away from; the lens looks at" the plane you want to have in focus. Now, unless you have asymmetrical tilts/swings, my procedure would be:

    For top/bottom points, I always focus first at the bottom of the ground glass (usually the more distant point) since I use field cameras with base tilts a lot. With axis tilts it doesn't matter. Anyway, I focus on the first focus point then tilt lens stage or camera back in the proper direction (i.e., "backing" or "looking") till both my chosen points are equally out of focus. Then refocus on the first point and then focus on the second point. If you have to rack out the bellows to get point 2 in focus, you need to move back or lens stage in whatever direction is needed to make the bellows a bit shorter. Vice-versa if you have to shorten bellows extension to get point 2 in focus. A couple iterations of this and you'll have both your points in focus.

    The above works for left/right focus points too, just substitute "left/right" for "top/bottom."

    For an oblique plane of sharp focus, you'll have to make adjustments for both top/bottom and left/right. It doesn't matter which you start with, however your focus points need to be directly opposite each other on the ground glass (i.e., vertically and horizontally aligned for top/bottom and right/left respectively). Apply one movement (say tilt), then apply the second (swing) using the method above. Then go back and check.

    It's really easier and faster to do than to explain.

    The next step for me is finding the focus spread between the nearest and farthest objects I want in focus in the scene (like Mark points out, there are always pesky objects that don't lie in your chosen plane ). If you've applied tilts/swings you need to really remember that the "near" is not necessarily what is nearest to you and the camera, but what is in front and/or above the plane of sharp focus and the "far" is what is behind and/or below the plane of sharp focus. I find the focus spread and note the bellows extension for each extreme. I then position focus exactly halfway between the two extremes and use the total distance to find the optimum f-stop to keep everything acceptably sharp (as described in the article on the LF home page, "choosing the optimum f-stop").

    Hope this helps,

    Doremus

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