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Tilted plane focus

Tilted plane focus is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tilted plane focus rather than just read about it. In short: Tilted plane photography is a method of employing focus as a descriptive, narrative or symbolic artistic device. It is distinct from the more simple uses of selective focus which highlight or emphasise a single point in an image, create an atmospheric bokeh, or miniaturise an obliquely-viewed landscape.

Tilted plane focus — main illustration
Tilted plane focus — illustration

Key takeaways

  • Tilted plane focus belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Tilted plane focus to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Tilted plane focus from memory before moving on to harder problems.

Reference excerpt

Tilted plane photography is a method of employing focus as a descriptive, narrative or symbolic artistic device. It is distinct from the more simple uses of selective focus which highlight or emphasise a single point in an image, create an atmospheric bokeh, or miniaturise an obliquely-viewed landscape. In this method the photographer is consciously using the camera to focus on several points in the image at once while de-focussing others, thus making conceptual connections between these points.

Limits to focus in imaging Focus is relative to spatial depth. Selective focus in photography is usually associated with depth of field. A pinhole camera generates an image of infinite relative focus, from a point just outside the camera opening out to infinity. Lenses focus more selectively so that, for objects near the lens, the distance between lens and sensor or film is increased and is shortened for more distant objects, to a point beyond which all is in focus. In telephoto lenses this point may be tens or hundreds of metres from the camera. Wide-angle lenses distinguish differences in depth only up to a short distance, beyond which all is in focus.

Depth of field Depth of field is an effect that permits bringing objects into focus at varying distances from the camera, and at varying depth between each other, into the field of view. A short lens, as explained above, will bring objects into focus that are relatively close to the camera, but it will also keep focus at greater distances between objects. A telephoto lens will be very shallow in its gamut of focus. Reducing the size of the aperture of the lens deepens the focus. At a pinhole size this will increase in effect, though the closer the objects are to the camera, the shorter the distance between focused objects.

Plane of focus Because focus depends on the distance between lens and the sensor or film plane, focus in the space in front of the camera is not on a point but rather on a plane parallel to the film plane. Spherical construction of lenses, rather than the ideal parabolic construction which is rarely and expensively achieved, means that this plane is slightly concave—more so in simple single element lenses and increasingly so with lenses of lower quality construction and materials. Compound lenses are built to correct this "spherical aberration" or "curvature of field".

Tilting the plane of focus

Varying the distance between the lens and sensor or film plane across the field of view permits focussing on objects at varying distances from the camera. One means of achieving this is to tilt the lens and/or the sensor or film plane in relation to each other. This will mean that individual points in the picture plane will focus on different points of depth, with the effect that the plane of sharp focus will tilt. This technique is based on the principle of Scheimpflug which, traditionally, is combined with small aperture to increase the gamut of focus beyond that achievable by depth of field alone. Usually no out-of-focus artifacts are desired in the image resulting from Scheimpflug adjustments. Here the converse is true. With the lens at full aperture, the photographer selects points in depth in the scene on which to focus and throws other points out-of-focus. This increases the contrast between the sharp and blurred areas and the selected application of focus and blur remains apparent to the viewer.

Tilted plane focus on smaller formats A view camera permits full, incrementally calibrated control over this technique, though it is possible to achieve with other cameras and formats. It is possible to achieve similar effects on a 35mm camera or digital single-lens reflex camera (DSLR) using a special tilt-shift lens, or by manually holding a lens that is removed from its mount.

History

Julia Margaret Cameron was a strong advocate of this use of selective focus. For example, in "Prayer and Praise", produced in 1865, there is a deliberate placement of focus at more than three points: on the face and parts of the body of the foreground child; and faces of mother and father; while a second child's face is thrown radically out of focus.

References

Notes

Citations

Bibliography Robin Gower (1991) Professional Photography, Australia, October, p. 15 Greg Neville (1990) 'A World of Fragments and Isolated Parts', The Age Melbourne, 9 August 1990, p. 14 Glenda Thompson (1990) 'The Bulletin/Mumm Cordon Rouge Champagne Photographic Awards', The Bulletin, Sydney, 6 November, p. 94-98

See also Angle of view Bokeh Circle of confusion Deep focus Depth of field Depth-of-field adapter Depth of focus Focus (optics) Frazier lens (very deep DOF) Hyperfocal distance Miniature faking Perspective distortion Shallow focus Tilt-shift photography View camera

Illustrations

Tilted plane focus: Example of tilted plane focus: here used for emphasis and metaphor, a 135mm lens at full aperture (f3.5) with extreme tilt and swing permits focus on specific details such as the foreground sack and slaughtered dingoes through to a section of the tennis-court mesh and the distant tethered goat. Shot on a 1963 Linhof Technica III 4"x 5" drop-bed field camera.
Example of tilted plane focus: here used for emphasis and metaphor, a 135mm lens at full aperture (f3.5) with extreme tilt and swing permits focus on specific details such as the foreground sack and slaughtered dingoes through to a section of the tennis-court mesh and the distant tethered goat. Shot on a 1963 Linhof Technica III 4"x 5" drop-bed field camera.
Tilted plane focus: Tilt-lens photo of a model train, shot with a DSLR camera with a 1.6x crop factor. The lens was swung towards right, in order to keep the plane of focus along the train. The sensor plane, the lens plane and the plane along the train all intersect to the right of the camera.
Tilt-lens photo of a model train, shot with a DSLR camera with a 1.6x crop factor. The lens was swung towards right, in order to keep the plane of focus along the train. The sensor plane, the lens plane and the plane along the train all intersect to the right of the camera.
Tilted plane focus: "Prayer and Praise" Julia Margaret Cameron, British, Freshwater, Isle of Wight, 1865. Albumen print 11 1/16 × 8 15/16 in. Note that the camera in this instance is tilted down toward the scene from a point above the subjects' heads. It is this angle which has forced the plane of focus obliquely into the scene, and direction of the adult models by the photographer would be necessary to ensure focus where it is placed precisely on their eyes
"Prayer and Praise" Julia Margaret Cameron, British, Freshwater, Isle of Wight, 1865. Albumen print 11 1/16 × 8 15/16 in. Note that the camera in this instance is tilted down toward the scene from a point above the subjects' heads. It is this angle which has forced the plane of focus obliquely into the scene, and direction of the adult models by the photographer would be necessary to ensure focus where it is placed precisely on their eyes

Worked examples

Example 1 — a first encounter with Tilted plane focus

Start with the simplest possible case. Write down what Tilted plane focus claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tilted plane focus before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tilted plane focus ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tilted plane focus

In research
Tilted plane focus appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Tilted plane focus in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Tilted plane focus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Photographic techniques, Science of photography, so understanding it makes those chapters shorter.
In everyday life
Look for Tilted plane focus outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Tilted plane focus in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Tilted plane focus means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Tilted plane focus out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tilted plane focus in simple terms?

Tilted plane photography is a method of employing focus as a descriptive, narrative or symbolic artistic device. It is distinct from the more simple uses of selective focus which highlight or emphasise a single point in an image, create an atmospheric bokeh, or miniaturise an obliquely-viewed lands…

Why does Tilted plane focus matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tilted plane focus?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tilted plane focus.

Tags

  • Photographic techniques
  • Science of photography

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