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Thread: How does rear tilt affect front tilt?

  1. #71
    Alan Klein's Avatar
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    Re: How does rear tilt affect front tilt?

    Quote Originally Posted by Doremus Scudder View Post
    Well, here's what I would do (a bit different approach than Vaughn and Kiwi).

    Since it's a building, I'd want the verticals parallel, so I'd set up the camera with the back level and check the verticals against the grid on my ground glass, adjusting the tripod tilt to get them right.

    Then I'd use a little bit of front tilt, using the nearest point on the ground at the bottom of the frame as the near reference point and the nearest point on the barn roof (likely the lower edge of the roof) as my far reference point. This would tilt the plane of sharp focus just a bit. I've found that this tiny bit of tilt normally allows me to use a larger aperture than not using movements.

    That focus position after the tilt was applied, i.e., with the ground at the bottom of the frame and the edge of the roof both in focus would then become my "near" focus point; I would note the position of the standards on the camera bed/rail.

    Then I'd look for the farthest point from that plane to use as my "far" focus point. That would probably be where the ground meets the base of the tree line far left, or maybe the distant hill behind the trees. I'd check both of them, focus on whichever one was most distant and then note the position of the standards on my camera bed/rail (I have mm scales on all my cameras just for this).

    I'd then note the difference between the "near" focus point position and the "far" focus point position. Just for fun, let's say that it's 3 mm. I'd set the focus exactly halfway between the two extremes, that is, at 1.5 mm shorter than the "near" position.

    Then, I'd check the handy table I have taped to the side of my camera that would tell me that for a focus spread of 3 mm, I need to use f/32.2. I'd set my aperture to the closest setting to that depending on the shutter speed (since speeds are in whole stops, I might have to choose a slightly smaller aperture).

    Then "click."

    BTW, the fact that you're using a 75mm lens for the shots you're posting means that with these, there will be very little focus spread between near and far, likely a mm or less. So, you don't have real depth-of-field issues with that lens. Try checking near/far positions in such scenes with a 210mm or 300mm lens and you'll quickly get into focus spreads of 4-6 mm or more.

    Best,

    Doremus
    I reviewed your various posts. Let's take this one step at a time if that's OK with you. See picture below for annotations. If I understand correctly, you first focus on A and then tilt for B focus. Note the spot on the rail. Then refocus from A to C. Note the spot on the rail. Move the standard so the final focus is halfway between A and C on the rail. Pick the f stop from the setting chart.

    Some questions regarding this photo's adjustments:
    1. When you refocus to C from A, doesn't B tilt point go out of focus? Are you supposed to re-adjust it into focus?
    2. Should the procedure be different if you use asymmetrical tilts with the back standard vs. the more traditional approach of using the front stand for tilting with a few iterations?
    3. Let's say there a large tree extending from the bottom to top in the foreground on the right. Then I understand that tilting won't work. The top ofm the tree will be out of focus. So you have to use only DOF calculations with an appropriate F stop. Where would you put the center focal point?
    Attached Thumbnails Attached Thumbnails Focusing.jpg  

  2. #72

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    Re: How does rear tilt affect front tilt?

    Quote Originally Posted by Alan Klein View Post
    I reviewed your various posts. Let's take this one step at a time if that's OK with you. See picture below for annotations. If I understand correctly, you first focus on A and then tilt for B focus. Note the spot on the rail. Then refocus from A to C. Note the spot on the rail. Move the standard so the final focus is halfway between A and C on the rail. Pick the f stop from the setting chart.
    Not 100% exactly, although you're basically correct. The far reference point for the tilt is close to "A," but likely more toward the near corner; anyway, whichever tall thing is closest. For "B" I'd pick an object way down on the foreground close to the edge of the frame. This is to make sure the plane of sharp focus starts out as close to the camera as possible, because in this particular case we're combining the position of the plane of sharp focus with with "near" focus point.

    A and B are reference points for the tilt, but remember, applying the tilt and swing is a separate step from focusing, so just keep in mind that that it's not always the case that the focus position after applying movements will equal your "near" focus point. More often, you'll have to apply the tilt and then find another "near" point to use as one of your two focus points.

    Note now, that after you've applied the tilt, that you are focused on a very near foreground object. This serves as the near focus point, so, yes, we note that position on the camera bed and find a far point to focus on. Your point "C" may not be ideal either (although pretty close - I'm picking nits here). Since we've applied tilt, the farthest point from the plane of sharp focus will be the farthest point below the plane of sharp focus, and is likely the horizon line, not treetops. So the most distant hills behind the trees and as low as possible is where I'd place that "far" point.

    But, you've got the method down. Note the point of the far focus on the camera bed and note the difference between your near and far focus on the camera bed. The final focus is halfway between the two extremes on the camera bed. The difference between near and far is what you use to choose the optimum f-stop; you consult your chart for this.


    Quote Originally Posted by Alan Klein View Post
    Some questions regarding this photo's adjustments:
    1. When you refocus to C from A, doesn't B tilt point go out of focus? Are you supposed to re-adjust it into focus?
    Yes, the tilt point will go out of focus! That's because the plane of sharp focus will move farther back in the scene and change position just a bit, allowing your depth of field to encompass both your near and far focus points. This is the desired outcome. So no, don't fiddle with the tilt/swing after setting it initially.

    Quote Originally Posted by Alan Klein View Post
    2. Should the procedure be different if you use asymmetrical tilts with the back standard vs. the more traditional approach of using the front stand for tilting with a few iterations?
    No difference at all. It doesn't matter whether you use front or rear tilts/swings or whether they are base, axis, asymmetrical or whatever The final relationship of film plane to lens plane is all that matters; you could hang them from skyhooks and move them around with telekinesis and it still wouldn't matter. Remember though, that the back position determines the rendering of perspective in the scene. If you don't want the verticals in that barn to converge, you want to make sure that the back is set up parallel to those lines, i.e., level and plumb, and then use front tilt to move the plane of sharp focus around.

    Quote Originally Posted by Alan Klein View Post
    3. Let's say there a large tree extending from the bottom to top in the foreground on the right. Then I understand that tilting won't work. The top of the tree will be out of focus. So you have to use only DOF calculations with an appropriate F stop. Where would you put the center focal point?
    With the near/far-split-the-difference focus method, you don't really do any depth-of-field calculations. The "central focal point" (I'm assuming you mean where the standards are finally positioned) is the same as before. You simply find near and far focus points, note the extremes and position the focus on the camera bed halfway between them. Of course, you've noted the distance difference between near and far points, so you consult your chart to find the optimum f-stop to use for that focus spread. No worries.

    There's one more thing to cover, just so you don't get confused. The scenario above, in which the position of the plane of sharp focus ends up equaling the near focus point, works only when you've used two very near objects as reference points for applying the tilt (or swing). This is very often not the case, so let's look at a situation that's a bit different:

    Imagine a wheat field that stretches up a hill to a distant oak tree, which is silhouetted against the sky. Of course, we want to apply tilt to lay the plane of sharp focus at the average position of the wheat field. But there are those pesky stalks of wheat in the foreground that are, say, three feet tall as well as a tall oak in the distance. Where should our reference points be? (Note: I use "reference points" to refer to the points we bring into focus for applying movements and "focus points" for the two points we use to determine near/far focus spread and then our final focus position.)

    Remember the wedge of depth of field that surrounds the plane of sharp focus when we tilt? That means, even in the foreground, the depth of field will be above and below our plane of sharp focus once we tilt, and we want to use every bit of it, especially close to the camera.

    So, we want to pick reference points for our tilt that are halfway up our near and far objects. So then, halfway up that distant oak tree for the far reference point; maybe a branch halfway up. And, for our near focus point, we want a point halfway up that near wheat stalk (so both the top or the bottom of it are included in the depth of field).

    So we set our tilt using those points and then, after the tilt is locked down, start looking for near and far focus points. Let's say that there is a head of wheat sticking up a little higher than the rest in the foreground, i.e., above the plane of sharp focus and closest to the camera. This will be the near focus point, which we now have to focus on because it is not in the same place as our plane of sharp focus. No matter, use the main focus knob to focus this near point and note its position on the camera bed.

    Now we need a far focus point. Since the plane of sharp focus is laying fairly flat in this scenario, the far focus point will be the most distant point below the plane of sharp focus. This will likely be the top of the distant hill at the base of the oak tree (NOT the top of the tree; that's above the plane of sharp focus and, therefore, "closer" than objects below the plane of sharp focus as far as the film is concerned). Note the position of the far focus point on the camera bed.

    Now all you have to do is set final focus halfway between the extremes and choose your f-stop based on the focus spread.

    Once you understand the basic principles of this method, it's really easy to use. It's just the counter-intuitive stuff involving tilts and swings in relation to what's "near" and "far" to the camera that can trip us up in the beginning.

    Hope this helps,

    Doremus

  3. #73
    Alan Klein's Avatar
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    Re: How does rear tilt affect front tilt?

    Doremus; Need time to digest. It's a lot. Thanks. Alan

  4. #74

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    Re: How does rear tilt affect front tilt?

    Quote Originally Posted by Alan Klein View Post
    Doremus; Need time to digest. It's a lot. Thanks. Alan
    Yeah, it's not hard, just a lot. Separating the steps helps. Practice just focusing the camera without messing with movements first. Then practice applying the movements without bothering about focusing and shooting. Then combine the two.

    Really, the only hurdle is visualizing the plane of sharp focus and the surrounding wedge of depth-of-field when tilt or swing is applied. If you have a good book on view camera movements (e.g., Stoeble) then there will be illustrations. There are also lots of illustrations on the web (just Google on depth of field and tilt), but be aware that many of them are erroneous in one way or other (e.g., one page I looked at stated that tilting the lens makes foreground objects "loom." Wrong! Tilting the back does that, but tilting the lens doesn't...).

    Anyway, keep at it, you'll master it eventually.

    Best,

    Doremus

  5. #75

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    Re: How does rear tilt affect front tilt?

    Quote Originally Posted by Doremus Scudder View Post
    Here's the pdf. Hope it helps.
    Awesome! I'm threatening to bust out the 4x5 for the first time in about 5 years, and was trying to remember this procedure. A very timely thread for me!

  6. #76
    Drew Bedo's Avatar
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    Re: How does rear tilt affect front tilt?

    I have not read most of the eight pages of this thread, so I may be redundent of just ignorent here . . . .But


    There are whiole books on this suff. Adems wrote three of them.

    Steve Simmons has a good book out (again).

    Kodak had a good book on LF .

    I have used a Kodak 2D in 8x10. It has no front tilt. I have at times tilted the whole camera down some and tilted the rear standard back to the virticle . . .simulating front tilt. Works for the table top stuff I did that way.

    Anolther thought regarding Near-Far issues: Some compositions just cannot be photographed as we see it with our inner eye.
    Drew Bedo
    www.quietlightphoto.com
    http://www.artsyhome.com/author/drew-bedo




    There are only three types of mounting flanges; too big, too small and wrong thread!

  7. #77

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    Re: How does rear tilt affect front tilt?

    I'm sure there are Drew,

    at the time when I asked the original question, I was in the Eastern Sierras on a camping trip. No photo books around, and very spotty cellular coverage. Basically only enough to post the question while I was in a small town and check a few days later when I had coverage.

    I'm glad it has generated a healthy discussion and it seems to be something others besides myself have had questions about. I've learned a lot, and am experimenting and practicing more at home before my next trip.

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