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Thread: How does rear tilt affect front tilt?

  1. #21

    Re: How does rear tilt affect front tilt?

    Quote Originally Posted by Doremus Scudder View Post
    ) ends up placing "near" objects above the plane of sharp focus and "far" objects below it.
    Excellent, I've definitely come to rely on what Mr. Luong calls the "Hansma" approach--one question I did have was that he seems to advocate making all of your movements first and only then using the focal scales to get the 1/2 delta between near and far bellows length. Is that your workflow as well?

    Otherwise, I think the conceptual problem I'm having is that I want to turn that two-dimensional "plane-of-focus" into a 3-D wedge--ideally a splitting maul instead of a cheese knife--to sweep as much of the foreground into focus as possible.

    FWIW, here's a shot that illustrates some of the problems I encountered last time out. Forum member Andy Tymon has been gracious enough to serve as a one-man Morbidity and Mortality Committee for me, but it would be very useful to me if others might let me know their workflow as well.

    57baleen2401A by J Barnes, on Flickr

  2. #22

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    Re: How does rear tilt affect front tilt?

    I try to visualize where I want my plane of sharp focus to lie before doing anything. Then I pick focus points (near/far; right/left) on that plane and take note of which other objects outside that plane would constitute the near/far focusing extremes. (Note: I've got two kinds of near/far points; the ones to adjust the plane of sharp focus to and then the extreme out-of-focus near/far points used to determine the focus spread - hope that's not confusing).

    Then, I'll fist apply the movements I need, getting my focus points in sharp focus and then, only after that, check the spread (delta, if you like) between the near/far out-of-focus points and stop down accordingly (after placing the focus halfway between, of course).

    However, there are some cases where I'll find near points to adjust movements to and then just find the spread between that and the most distant point. For example: let's say I have an architectural shot; a tallish building with foreground. My focus points for applying movements will be the closest object in the foreground that I want in focus and the nearest tallest point of the building. I'll use front tilt to get these in sharp focus (keeping the back parallel to the building) ending up with the plane of sharp focus tilted away from parallel slightly. Then, I'll find the farthest point in the scene, find the focus spread, split the difference and stop down accordingly.

    I might have used this method for the shot you posted. With close-up shots, like yours, you may find that the focus spread is rather large. For tricky shots like this, I'll sometimes pick several different sets of focus points and out-of-focus near/far points and try each of them to see which gives me the least spread. However, you may find that you simply need to stop down a lot for the needed depth-of-field. I don't hesitate to stop down to f/45 if needed, just keeping in mind that I won't be able to print as large due to diffraction degradation.

    Hope this helps,

    Doremus

  3. #23

    Re: How does rear tilt affect front tilt?

    Quote Originally Posted by Doremus Scudder View Post
    For tricky shots like this, I'll sometimes pick several different sets of focus points and out-of-focus near/far points and try each of them to see which gives me the least spread. However, you may find that you simply need to stop down a lot for the needed depth-of-field.
    Well, the heat indices have been pushing triple-digits lately, so the whole "f/45 and be there" thing sounds like a plan

    Thanks so much for the detailed reply--the idea of having two sets of focus points clarifies things greatly!

  4. #24
    Vaughn's Avatar
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    Re: How does rear tilt affect front tilt?

    ...It's a bit of a long read, but well worth it. In short, however, you simply measure the distance difference between front and rear standards focused on the nearest and farthest object you want in sharp focus and choose your f-stop accordingly...
    After a few decades of focusing, I have included the above in my bag of tricks. In the past I have done something a little different that leads one basically to the same results: After determine near-and-far points and side points, I take a general guess of where to place the focus and I apply basic movements and adjust the focus a little to match. Then on the GG I watch my focus points as I start closing the aperture...if my focus points all become sharp to my eye at about the same time, I got the focus plane (including the amount of tilt, etc) in the right place. I get them all as sharp as my eyes can tell (pretty good), then check the aperture -- then close down one, but often two or more stops (contact printing). If my further points had come into sharpness on the GG before the near points, that would have told me to focus a little closer in...and so forth.

    It is sort of a visual way of doing what Doremus is suggesting. I have found Doremus' method much easier with my 11x14, as sometimes the focus points are too spread out to see at the same time (150 sq inches is a bit of real estate), or too dark under the redwoods to see much at f22, and so forth. So Doremus' method gets me very close to my final focus. But it would be easier to have some type of scale on the camera or take a ruler. I still try to double check using my old system...habit.

    I do not always place the plane of focus on its 'optimal' location. I might move the focus just a little to favor the composition...changing the image size to allow a branch to intersect a corner, for example, then and closing down enough to counter it. Or to put a razor sharpness on one portion of the image while letting the rest still be in focus....just not quite so focused, so to speak.
    "Landscapes exist in the material world yet soar in the realms of the spirit..." Tsung Ping, 5th Century China

  5. #25
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    Re: How does rear tilt affect front tilt?

    Quote Originally Posted by Doremus Scudder View Post
    I try to visualize where I want my plane of sharp focus to lie before doing anything. Then I pick focus points (near/far; right/left) on that plane and take note of which other objects outside that plane would constitute the near/far focusing extremes. (Note: I've got two kinds of near/far points; the ones to adjust the plane of sharp focus to and then the extreme out-of-focus near/far points used to determine the focus spread - hope that's not confusing).

    Then, I'll fist apply the movements I need, getting my focus points in sharp focus and then, only after that, check the spread (delta, if you like) between the near/far out-of-focus points and stop down accordingly (after placing the focus halfway between, of course).

    However, there are some cases where I'll find near points to adjust movements to and then just find the spread between that and the most distant point. For example: let's say I have an architectural shot; a tallish building with foreground. My focus points for applying movements will be the closest object in the foreground that I want in focus and the nearest tallest point of the building. I'll use front tilt to get these in sharp focus (keeping the back parallel to the building) ending up with the plane of sharp focus tilted away from parallel slightly. Then, I'll find the farthest point in the scene, find the focus spread, split the difference and stop down accordingly.

    I might have used this method for the shot you posted. With close-up shots, like yours, you may find that the focus spread is rather large. For tricky shots like this, I'll sometimes pick several different sets of focus points and out-of-focus near/far points and try each of them to see which gives me the least spread. However, you may find that you simply need to stop down a lot for the needed depth-of-field. I don't hesitate to stop down to f/45 if needed, just keeping in mind that I won't be able to print as large due to diffraction degradation.

    Hope this helps,

    Doremus
    I'm new to LF. So my Chamonix camera has asymmetrical tilt only with the back standard. You focus on the far point at the rear standard axis line and then tilt the back standard to focus the near focal point. So if I was to split the difference afterwards as you do and move the standard (rear?) (front?) focus point halfway between near and far focus points, wouldn't I have destroyed the whole point of the camera's asymmetrical tilt?

    Let's say I do the same thing the standard non-asymmetrical LF way by using a number of iterations of rear focus and front standard tilt. Again, if I move the standard to the middle, wouldn't I lose the whole process?

    What am I missing?

  6. #26

    Re: How does rear tilt affect front tilt?

    Quote Originally Posted by Vaughn View Post
    Then on the GG I watch my focus points as I start closing the aperture...if my focus points all become sharp to my eye at about the same time, I got the focus plane (including the amount of tilt, etc) in the right place.
    Very helpful, Vaughn--and I definitely envy your ULF GG...going to 5x7 from 4x5 was a game changer for me, so I can imagine what twice the acreage must be like.

    One thing I'm curious about, given what I've seen of your subjects, is how often you use tilt/swing--I'm still a little chary given how often I have vertical elements (i.e. trees, and lots of 'em) in the frame.

  7. #27

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    Re: How does rear tilt affect front tilt?

    Quote Originally Posted by Alan Klein View Post
    I'm new to LF. So my Chamonix camera has asymmetrical tilt only with the back standard. You focus on the far point at the rear standard axis line and then tilt the back standard to focus the near focal point. So if I was to split the difference afterwards as you do and move the standard (rear?) (front?) focus point halfway between near and far focus points, wouldn't I have destroyed the whole point of the camera's asymmetrical tilt?

    Let's say I do the same thing the standard non-asymmetrical LF way by using a number of iterations of rear focus and front standard tilt. Again, if I move the standard to the middle, wouldn't I lose the whole process?

    What am I missing?
    Alan,

    I think you are confusing applying tilts/swings (i.e., positioning the plane of sharp focus) with determining the optimum f-stop from near and far points that you want to be in sharp focus.

    Yes, you need focus points to apply your tilts and swings too, but they are not the same ones Applying tilts/swings is a different thing than finding a focus spread in order to determining the optimum f-stop.

    With asymmetrical movements, one of the focus points is always on the axis line, which you focus on with the main focusing (i.e., bellows extension) The other point is one you choose on the opposite side to swing/tilt into focus. This is how you get near/far or right/left objects in the same plane of focus. However, this isn't finding the focus extremes to determine your f-stop.

    Once you have applied your movements, THEN you look for objects that are outside the plane of sharp focus. You want to choose the nearest and the farthest point from that plane that you want in sharp focus. THESE are your focus points for finding the optimum f-stop. You focus on one extreme, note the position of the standards on the rail/camera body, then focus on the other extreme and note that position. The distance between the two extremes (the focus spread) will tell you what your optimum f-stop should be (having a mm scale or ruler on your camera helps a lot to determine this. All my cameras have mm scales taped on.)

    For the final shot, you focus, i.e., position the standards, exactly halfway between the two extremes on the rail/camera body (NOT focus on an object halfway between those extremes in the scene! - Just pay attention to the actual physical distance between standards).

    If you read the article on determining the optimum f-stop that I linked to above, you will find everything you need to know about which f-stop to choose for whatever focus spread you have.

    What I was trying to point out to Creation Bear above is that when you apply, say, a lot of tilt, the plane of sharp focus can be horizontal in the scene. In that case, "nearer" objects are above the plane of sharp focus and "farther" ones are below the plane of sharp focus. So, if you have this configuration, the "nearest" object would be the one that is closest to the camera and above the plane of sharp focus (this could be a flower sticking up from the foreground). The "farthest" would be the one below the plane of sharp focus farthest from the camera (this could be the base of a mountain where it meets the plain if you've positioned your plane of sharp focus halfway up the mountainside. - Note that the peak of the mountain would then be above the plane of sharp focus and actually "closer" to the camera optically!).

    Hope that clears things up.

    Doremus

  8. #28
    Alan Klein's Avatar
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    Re: How does rear tilt affect front tilt?

    Quote Originally Posted by Doremus Scudder View Post
    Alan,

    I think you are confusing applying tilts/swings (i.e., positioning the plane of sharp focus) with determining the optimum f-stop from near and far points that you want to be in sharp focus.

    Yes, you need focus points to apply your tilts and swings too, but they are not the same ones Applying tilts/swings is a different thing than finding a focus spread in order to determining the optimum f-stop.

    With asymmetrical movements, one of the focus points is always on the axis line, which you focus on with the main focusing (i.e., bellows extension) The other point is one you choose on the opposite side to swing/tilt into focus. This is how you get near/far or right/left objects in the same plane of focus. However, this isn't finding the focus extremes to determine your f-stop.

    Once you have applied your movements, THEN you look for objects that are outside the plane of sharp focus. You want to choose the nearest and the farthest point from that plane that you want in sharp focus. THESE are your focus points for finding the optimum f-stop. You focus on one extreme, note the position of the standards on the rail/camera body, then focus on the other extreme and note that position. The distance between the two extremes (the focus spread) will tell you what your optimum f-stop should be (having a mm scale or ruler on your camera helps a lot to determine this. All my cameras have mm scales taped on.)

    For the final shot, you focus, i.e., position the standards, exactly halfway between the two extremes on the rail/camera body (NOT focus on an object halfway between those extremes in the scene! - Just pay attention to the actual physical distance between standards).

    If you read the article on determining the optimum f-stop that I linked to above, you will find everything you need to know about which f-stop to choose for whatever focus spread you have.

    What I was trying to point out to Creation Bear above is that when you apply, say, a lot of tilt, the plane of sharp focus can be horizontal in the scene. In that case, "nearer" objects are above the plane of sharp focus and "farther" ones are below the plane of sharp focus. So, if you have this configuration, the "nearest" object would be the one that is closest to the camera and above the plane of sharp focus (this could be a flower sticking up from the foreground). The "farthest" would be the one below the plane of sharp focus farthest from the camera (this could be the base of a mountain where it meets the plain if you've positioned your plane of sharp focus halfway up the mountainside. - Note that the peak of the mountain would then be above the plane of sharp focus and actually "closer" to the camera optically!).

    Hope that clears things up.

    Doremus
    Sorry, I'm still confused. The bold part. Do you refocus a second time? Doesn't that eliminate the original far focus and tilt focusing you just completed if you set the focus in the middle between the far and near focus points? I don't understand this procedure.

  9. #29

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    Re: How does rear tilt affect front tilt?

    Quote Originally Posted by Alan Klein View Post
    Sorry, I'm still confused. The bold part. Do you refocus a second time? Doesn't that eliminate the original far focus and tilt focusing you just completed if you set the focus in the middle between the far and near focus points? I don't understand this procedure.
    Invest a few dollars on the Rodenstock pocket Scheimpflug/depth of field calculator and it will all become crystal clear. Fits a shirt pocket, no batteries and will also give you exposure corrections and the proper focus point between near and far points.

  10. #30

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    Re: How does rear tilt affect front tilt?

    Quote Originally Posted by Alan Klein View Post
    Sorry, I'm still confused. The bold part. Do you refocus a second time? Doesn't that eliminate the original far focus and tilt focusing you just completed if you set the focus in the middle between the far and near focus points? I don't understand this procedure.
    First you set/tilt the focus plane to make your optimal focus. Then you assess how much DOF you need by measuring the focus spread. That is focusing closer and farther away from your focus plane to see what you want included in your DOF. There could be things that's not in the focusing plane but that you want to be sharp.
    Depending on the focusing spread your optimal focusing plane can be offset from your initial focusing plane (not refocused, just offset, you don't look on the gg for this, just measure and move on the rail). Example, you might want to include something in the foreground in your DOF but your far focus plane is already at the infinity. In that case you need to shift the focus plane closer to even out the DOF between far and near objects.
    If you don't do that you need to stop down too much to get that DOF for the foreground object and add unnecessary diffraction.

    It's all about balancing sharpness from DOF and unsharpness from diffraction.

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