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  1. #21
    L Gebhardt's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    1.Situations where there is a lot of depth and multiple planes, and tilts and swings cannot be used:
    ·How do you decide where to focus?
    ·Do you use “conventional” depth of field rules?
    ·Do you focus on the near objects?
    ·Do you focus at a hyperfocal distance (ie focus on nothing)?
    ·Do you use Merklinger’s “object plane” method (usually resulting in an infinity bias)?
    ·Do you focus at infinity?
    ·How do you determine depth of field?
    ·Do you simply use the near-far focus method?
    In this case you can't really use tilts or swings unless one plane is much more important than another. But in most cases like this I find movements make the image look weird. For example adding a swing to get a receding wall in focus works, but if the objects on other planes are out of focus at different distances it's odd to my eye. So in this case I either find the subject and focus on that and let the rest stay blurry, or I focus on the subject and stop down enough to bring the rest into focus. Sure diffraction will rob you of some sharpness, but you can still make a pretty decent 16x20 print from a 4x5 at f/32 or higher. Only if there are two subjects at different distances do I focus between them (about a 1/3 of the way, but I do this by feel of the focus knob, not direct measurement so it's rough).

    I don't usually bother with DOF charts since all the lookups distract me and ruin the experience. I usually can see well enough on the ground glass with a loupe to know if I'm close. I then close down one more stop from experience. If in doubt close down more and deal with the diffraction blur later. I've learned the hard way that you can still get a good print when diffraction has blurred it (just at a smaller print size), but you can salvage a shot where there is awkward out of focus areas.

    I almost never focus at infinity, as you are wasting a lot of DOF that could let you open up a bit. The one exception would be if the subject really is at infinity (and there is nothing closer), in which case you could shoot that at what ever aperture you want.

    Quote Originally Posted by Michael R 1974 View Post
    2.Situations where tilt can be used:
    ·How do you decide where to focus?
    ·Do you determine the tilt angle?
    ·If you use Merklinger’s methods and the hinge rule, how do you determine where the plane of sharp focus should be? How far below the lens should the hinge line be? How do you estimate all the distance measurements involved? How do you decide on the angle the plane of sharp focus should take from the foreground to the background? Etc etc (there are so many variables in this).
    ·How do you determine what lies within the depth of field? The math might work nicely on a diagram, but in the field how do you really figure out where things are in the space in front of you?

    Thanks
    I determine which plane I want to focus on when I'm not looking through the lens. This lets you see in three dimensions and spot things away from the plane that will look odd if they get blurry as you move away form the plane (think trees with blurry tops). I usually tilt the lens and determine it by eye making sure the plane is in focus both near and far. I then look at the camera from the side and check if it confirms to the Scheimpflug principle. If it doesn't I know something is wrong. I then stop down enough to make sure all the trees and other things are sharp to the tips. Remember to check the tallest/farthest objects from the plane (in reality picture a wedge going out along the plane). These will be where the problems are. And I stop down one stop to account for my eyes and the loupe, as above. When using movements I am almost always trying to get the whole scene in focus. If not I generally find things look odd.

    I never bother with the math, and hadn't heard of Merklinger’s methods until this post. A simple visualization of the Scheimpflug picture works well for me. It's easy enough to see if you step to the side of your camera.

  2. #22

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    I'm surprised these haven't already been mentioned:

    http://www.largeformatphotography.in...-to-focus.html
    http://www.largeformatphotography.info/fstop.html

    I find the method described in the second article (How to Select the f-Stop) best for me. I have equipped my field cameras with millimeter scales and have taped a table of optimum f-stops to the camera body. Focus near-far, split the distance, set the f-stop based on the spread and shoot.

    This I modify a bit when the horizon is in the scene and things at infinity are important. In this case (as per Merklinger's advice), I cheat toward the infinity a bit, focusing about 20% farther back (shorter) than halfway. Sometimes I'll use a bit smaller f-stop in this case as well.

    For swings and tilts you use the same method with one caveat. When you reposition the plane of sharp focus with swings/tilts, the objects that are optically nearest and farthest in the scene are often counter-intuitive. For example, when using tilt to get a foreground object and a mountaintop in focus, the base of the mountain (even though it's physically closer) will become the farthest from the plane of focus. It takes a bit of practice to learn where the best positioning of the plane of sharp focus is for complex scenes. One way to tell if you have an optimum positioning is to measure the focus spread for various amounts of tilt/swing. The position with the least spread is the best and can use a larger aperture for the same amount of sharpness, which is usually more desirable.

    Hope this helps,

    Doremus

    www.DoremusScudder.com

  3. #23
    henk@apug's Avatar
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    How do you focus your camera?

    Quote Originally Posted by Doremus Scudder View Post
    I'm surprised these haven't already been mentioned:

    For swings and tilts you use the same method with one caveat.

    www.DoremusScudder.com
    I can not get my head around this: when you position the plain of sharp focus with a tilt
    and use a near and far point to do so then these two points are in focus when the tilt is correct,
    so there is no difference in distance on the camera for these two points.

    With a "zero" camera setup I totally understand the technique of near and far points because
    there "is" always a distance on the camera between those two points, then devide by two
    to set camera and multiply by 5 for aperture setting (5 in case of a 4x5 camera).
    But with a tilt the near and the far point are both in focus for the same distance on the camera
    when the tilt is correctly setup for the plane of sharp focus one has in mind.

    Could you please explain some more this method when using tilts ?

    Thank you !
    Last edited by henk@apug; 01-05-2013 at 04:11 PM. Click to view previous post history.

  4. #24
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    How do you focus your camera?

    ok, I got it
    I read links Doremus provided, answers are in there

  5. #25
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    Quote Originally Posted by Michael R 1974 View Post
    CPorter: Regarding the hinge rule, how do you personally estimate the distance J?
    I apologize for such a late response, I never saw this question, but I'll try to provide one here..........

    I step out from behind the camera and stand to the side and look at the far element and invision the plane of sharp focus to the near element, then continuing toward the camera past the near element, eventually the plane of sharp focus passes through the ground where it will intersect a vertical plane through the lens that is parallel to the film (or more simply just the height of the lens above the sharp plane of focus for the distance "j").

    It's a guess as to how many feet below the lens, through the ground, where the plane you want sharp is intersecting the "parallel to film lens plane", which also should be projected through the ground where the two meet at the "hinge". I've never nailed it the first time, but it has gotten me pretty close, then it has to be tweaked from there. One thing to remember is that when tilting the lens, the plane of sharp focus tilts more than the degree of tilt you actually gave the lens itself. So if your're only tilting the lens, say, 3 degrees, then you know that the plane of sharp focus is tilted more than 3 degrees. By how much is not important, just know that is the case.

    Howard Bond's "Focus-Check" procedure will get you there just the same, in fact, I have used the calculation to estimate tilt angle, then I have used Bond's procedure to do the tweaking. Sometimes I have just used Bond's focus-check to arrive at the plane I want in focus. It takes some practice, but when you understand it, it becomes second nature.....I would do a lot of practicing around the house/yard before I even put film in the camera.

    The last thing I think one should remember is that Merklinger states that DoF is maximized with an untilted lens, because an untilted lens does not present a "cone" shaped DoF region in front of and behind the plane that is sharply focused, narrow end of the cone is closest to the lens. When the lens is tilted, the subject should not have tall elements that are near the camera, they should be much closer to the "far" elements due to the cone shaped DoF. But of course, never using lens tilt in order to maximize DoF, means that you probably are not getting the most out of your LF camera system.

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