lens shift

Discussion in 'Beyond the Basics' started by den9, Aug 26, 2010.

  1. den9

    den9 TPF Noob!

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    does this make sense?
    Technorama Shiftadapter

    i understand tilt and ****, but wouldnt this be no different then raising the tripod 10mm or so?
     
  2. Helen B

    Helen B TPF Noob!

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    No, it's not the same. If you raise the tripod 10 mm all that happens is that your field of view rises 10 mm. If you use lens rise (shift vertically upwards) then the field of view looks up at an angle. even though the film/sensor plane may be perfectly vertical. It's easier to describe graphically than in words, so try reading the Wikipedia entry on lens rise and fall.
     
  3. den9

    den9 TPF Noob!

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    so if i shift the lens up 10mm ill get the top of the building, and if i raise the tripod ill get the top of the building, but converging lines, even if the camera is dead level and flat?

    if i had that camera and wanted to get shoot that building shown on the original link, how do i determine how high to set my tripod?

    thanks for helping me out, this is very important to me.
     
  4. Helen B

    Helen B TPF Noob!

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    Imagine a camera mounted perfectly level on a tripod. The lens axis (the line through the middle of the lens) is perfectly horizontal. At one end (the camera end) it passes through dead centre of the image and at the other end it passes through the front of a building, at a point which is at exactly the same height as the camera. It is dead centre in the field of view. In our imaginary case we see that with the camera level, we are cutting off most of the building's roof.

    Because the film/sensor plane is perfectly vertical, there is no convergence of the buildings vertical lines.

    Now, if I raise the tripod column 10 mm all that happens is that I see 10 mm more of the building's roof.

    If, instead of raising the camera, I simply raise the lens while keeping the back stationary the lens axis will remain horizontal, but the line between the centre of the film/sensor and the "centre" of the lens will rise up above the vertical. It is this line that defines the field of view. Therefore the camera is now looking up, and 10 mm of lens rise translates into a much greater rise in the field of view.

    Suppose you have a 50 mm lens, and you raise it 10 mm. On a building 50 m (about 150 ft) away the field of view will rise 50 000/ 50 x 10 = 10 000 mm, or 10 m (about 30 ft). The film/sensor is still vertical, so building verticals will remain straight and vertical in the image.

    How does that sound?

    Best,
    Helen
     
  5. den9

    den9 TPF Noob!

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    I sort of understand, your saying its the same effect as tilting to lens up to get the whole building, without converging lines. But doesn't this camera just shift up and down, not tilt? It took me awhile to understand the canon tilt shift lens, but this linhof seems like it justs goes up and down, no tilting though. It just doesn't make sense to me, its driving me nuts.
     
  6. Derrel

    Derrel Mr. Rain Cloud

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    "Shift" is not the same as tilt, so den9 your intuition is treating you well. Shifting the lens's position while maintaining the same,identical "film position" is a well-regarded way to make stitched panoramic photographs. Rest assured, the folks at Linhof know what they're doing, and Linhof 617 users are technically-minded,serious landscape and architecture shooters who will be wetting themselves at the prospect of having a shift version of this well-regarded camera.
     
  7. Helen B

    Helen B TPF Noob!

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    Tilt doesn't have much effect on the field of view, just on the plane of sharp focus. It is shift (rise and fall when in the vertical direction) that affects the field of view. That is why many lenses for architectural use only have shift, such as this Schneider PC Super Angulon:

    [​IMG]

    We prefer to hold the lens in the same position while shifting the back - this keeps the point of view the same for each shot.

    Best,
    Helen
     
    Last edited: Aug 27, 2010
  8. den9

    den9 TPF Noob!

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    so for converging lines, you need to keep the camera level to avoid them

    and tilting has nothing to do with fixing converging lines, just shifting? correct?

    and with the linhof 617 it doesnt have converging lines anyway, if its straight correct?

    and the shift plate adaptor is just so you can make stitching photos better?
     
  9. Helen B

    Helen B TPF Noob!

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    Yes, unless you want to correct them in post. Specifically you need to keep the film/sensor plane vertical. That does not always mean that the camera itself has to be level - some cameras have rear tilt. Rear tilt affects both converging lines and plane of focus; lens tilt only affects plane of focus.

    Correct. Ideally tilting only affects the plane of focus, not the perspective or the field of view. There may be a slight change in the field of view if the lens is not tilted about the rear (second) nodal point or because the entrance pupil is not coincident with the rear nodal point - but these should be slight changes in field of view. Shifting affects field of view, thus allowing the back to stay vertical while the camera 'looks up'. Shifting itself does not change converging lines - ie as you shift a lens you do not see any change in the verticals of a building, only in field of view.

    Only if the camera back is vertical (= camera is level: Technorama does not have rear tilt).

    Not quite. The shift plate adapter primarily allows the camera to 'look up' while the camera is level. It also allows perfect stitching, because it holds the lens stationary while the back moves up and down.

    Best,
    Helen
     
  10. den9

    den9 TPF Noob!

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    so if the camera is horizontal, and you take a skyline picture from across a river, will you need to shift up to prevent converging lines?

    what does shifting down do?

    why doe it not create converging lines when vertical?

    have you ever checked out horst hamanns new york vertical book?

    will you buy me a linhof 617 with a 72mm lens?

    thank you so much for all the help! some reason im assuming you own or have experience with this camera?
     
  11. den9

    den9 TPF Noob!

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    damn i just thought of another thing

    how can you tell how much shift you need since you arent looking through the lens, and since the view finder doesnt raise up, how do you know you are getting the building in the shot?

    this camera is very confusing and expensive, but some day i will get one.
     
  12. Helen B

    Helen B TPF Noob!

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    If the camera is horizontal you do not need shift to prevent converging verticals. You only need shift to move the field of view up (or down) to get the framing you would like.

    It moves the field of view downwards.

    It would, if the camera was not level. The vertical angle of view is so great that you may not need to shift in order to get the top of a building in when the camera is level. You just crop out the bottom part of the picture.

    No, but I'll check it out.

    I would like to be able to!

    Not with the 617 with shift adapter. I've used the plain 617, and other similar roll film cameras that have shift systems. I have used large format cameras with tilt and shift for over thirty years, and I have both shift and tilt-shift lenses for my 35 mm / digital SLRs.

    That's really what the ground glass back is for. Some cameras link the lens shift to a viewfinder angle shift.

    Best,
    Helen
     

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