by Q.-Tuan Luong for the Large Format Page
In practice, what I personally use is procedure I (focus on far, tilt on near) when photographing mostly flat/planar subjects. When the subject is tall, most of the time I use procedure II, going directly to step 2 (spread focus between far and near). If this results in a very small aperture (f45 or worse), I might try the full procedure II (minimize focus spread with tilt) to get a larger aperture.
I recommend using a metric scale. It is also necessary for the optimal determination of the f-stop.
We all know that when a rigid camera is focused, all the objects which are at a same perpendicular distance from the film plane can be brought in focus at a time. For a rigid camera, the film plane and the lens plane are parallel (or equivalently intersect at infinity). So the subject plane must also be parallel to these two planes.
In a view camera, the geometric relationship between the film plane (the back standard) and the lens plane (the front standard) can be adjusted. This makes it possible to focus on virtually any plane, be it receding or slanted.
To use the Scheimpflug rule, here are a few points to keep in mind:
To adjust the tilt, use the following. To adjust the swing, replace "top/bottom" by "left/right".
Variations of this technique:
The procedure is described for tilt adjustment only. Same considerations as before apply for swing. The idea is simple: by successive trial and error, you will determine the tilt which is such that the focus spread is minimized (step 1). Then you determine the optimal focus point (step 2).
The idea behind step 1 can be used without applying the full procedure. For instance, you have a distant landscape with some tall trees in the foreground. Since this is not planar, you'll have to stop down. If you shoot without movements, focussing somewhere behind the trees, the trees and the horizon will be out of focus and require stopping down. If you tilt the lens, focussing somewhere on 2/3 the height of the trees, the bottom and top of the trees will be out of focus and require stopping down. Which of the two alternatives is the best ? The answer is given by measuring the focus spread for each of them, and seeing which one is the smallest.
One class of methods are based on measurements on the camera and computations. They require a calculator such as the Rodenstock tool or Bob Wheeler's Vade Mecum which runs on palm devices. Both are detailed in Bob Wheeler's Photographer's Aids: A survey. In particular, Bob Wheeler gives a in Notes on view camera geometry a practical rule for use in the field. Wheeler's rule states that the angle of tilt is 60*delta_focus/delta_GG, where:
There is also a method developed by Harold Merklinger in his book "Focusing the View Camera", and well summarized on his web site. This site in particular has a few brilliant animations which are very helpful in visualizing the Scheimpflug. Merklinger points out to a rule complementary to the Scheimpflug, called the "hinge rule". His method calls for the measurement of the distance J from the lens to the required plane of sharp focus, measured parallel to the film, and the use of a table to get the tilt value. Personally I think this a great geometric analysis, but that in practice it is not easy to apply because J is not that easy to estimate. For a discussion on the practical feasibility of this approach, see this QA forum thread and this one. If you want to try to use this approach, this Excel file might help.
For the historically inclined, Harold Merklinger's page has the 51-page Theodor Scheimpflug's 1904 British Patent. For the geometrically inclined, I sketched an elegant (I think) geometric proof of the Scheimpflug's principle using Desargues theorem. An essentially identical derivation is given in Bob Wheeler's excellent Notes on view camera geometry. Generally speaking, these notes are some of the best exposition of the math behind view camera operation that I have seen.
Subsequently, Emmanuel Bigler sent me a new derivation (Scheimpflug's rule: a simple ray-tracing for high school ?) which requires only high-school level (well, French high school from the 60s) geometry. He then goes on to show geometrically, using an absolute minimum of algebra how to derive the position of the slanted planes defining the DOF area (Depth of field and Scheimpflug's rule: a minimalist geometrical approach).
A number of great technical/mathematical notes can also be found on this page by professional mathematician and photographer Leonard Evens. Of particular interest is the thorough View Camera Geometry. Originally intended as a relatively short article for the American Math Monthly, it soon got too large for that, approaching book length at 105 pages (in the spirit of Wheeler's notes). It does address a whole lot of issues that arise in the use of a view camera from an analytic, mathematical point of view. That page has also the more focused, but formula-free (and therefore more accessible to those familiar with geometry) Depth of Field for the Tilted Lens.
Howard Bond describes with plenty of details his well-proven method in his article, Setting Up the View Camera (reproduced on this site). The idea of biasing the focus towards infinity in landscape photography is discussed by Harold Merklinger's The INs and OUTs of FOCUS, and in the article by Joe Englander, Apparent Depth of Field: Practical Use in Landscape Photography.
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