Talk:Scheimpflug principle/Archive 1

Illustrations

I think this page could use images to illustrate the Scheimpflug rule. I'm new to wikipedia so maybe someone else could figure out how they are added?

Thanks! C — Preceding unsigned comment added by 1p2o3i (talk • contribs) 18:06, 26 November 2006 (UTC)

Edit of 25 April 2007

I've made a first attempt at cleaning things up a bit. A few specific comments:

• I changed "focus plane" to "plane of focus" for two reasons: 1), the latter gets roughly twice as many hits on a Google search, and 2), more important, it seems less likely to be confused with "focal plane" (which apparently was the case with the previous link).
• I revised the description of the macro photograph, because it doesn't employ the Scheimpflug principle.
• I eliminated mention of claims that the Scheimpflug principle creates infinite DoF, because it didn't seem relevant—focus and DoF are separate issues. If someone insists on restoring this comment, a link to at least one source would be helpful (I'll quickly concede, of course, that I don't have a verifiable source for "anti-Scheimpflug").
• I retained the wording "oblique tangent", with some reservations (I understand "oblique" and "tangent", but quite honestly, I still don't quite understand "oblique tangent" ...)
• I retitled "References" to "External links" because none of the links technically meets WP criteria for verifiable sources. I think removing these links would be a great mistake, however, because I'm not sure there are any sources that would strictly qualify. Moreover, though self-published, Merklinger has been widely cited and discussed, and his diagrams remain the best available. Wheeler includes fairly complete derivations, so the reader can verify his results for herself. The "Tilt and Shift" link also includes considerable useful information, such as a clear demonstration that increasing tilt decreases angular DoF.
• I don't think WP is the best place to be creating new terms, but in the case of the axis about which the PoF rotates, there may be no choice, as there simply is no standard term. "Counter axis" seems unintuitive, "hinge line" seems a bit informal, and planes intersect at lines, so "pivot point" doesn't seem quite right, either. Things generally rotate about axes, so "rotation axis" or "PoF rotation axis" seem the most descriptive, if not especially elegant. "Pivot axis" might be another possibility.

I think diagrams of the PoF rotation and the wedge-shaped DoF would be helpful; I have both, but they need some minor reformatting. They won't quite match the current diagram, but a slight hodgepodge may be preferable to nothing. An image similar to the text closeup, but with the PoF coincident with the paper would also seem useful; I have a round tuit here somewhere that I just need to get ... JeffConrad 09:27, 25 April 2007 (UTC)

I've removed the cleanup tag. The editor (Vanderdecken) who added the tag gave no specifics, but the edits of 25–26 April 2007 made substantial changes, and there has been no subsequent comment, so I'll assume that most of the concerns have been addressed. This hardly is to suggest that the article would not benefit from additional work. JeffConrad 22:25, 13 May 2007 (UTC)

Change to Depth of Field section

I changed the phrase "smaller lens f-number" to "larger lens aperture," because, as a photographer, I feel this phrasing better conveys the idea that the wedge-shaped DoF allows a photographer to create photographs that utilize a greater DoF than would be available using parallel planes of focus (ie, with cameras that do not allow movement of the lens and image planes). Though it is purely a semantic difference (a smaller f-number = a larger aperture), I, myself, tend to think in terms of aperture size; thus, for increased DoF, I would think to use a "smaller aperture," rather than "larger f-number." —Preceding unsigned comment added by 71.38.145.27 (talk) 18:37, 21 February 2008 (UTC)

Phonetics

Can we get a pronounciation guide on this article for "Scheimpflug"? 82.10.108.49 (talk) 22:00, 10 April 2008 (UTC)

Diagram description

The text doesn't explain what the "Lens object focal plane" in the diagram represents, nor does it mark "J" or theta from the equation on the diagram. It would be helpful if the equation and the diagram used the same symbols.

RobertSeber (talk) 16:04, 9 June 2008 (UTC)

What sort of explanation of "lens object focal plane" are you looking for? The linked article gives a reasonable description, though perhaps it doesn't address your question.

RobertSeber (talk) 06:37, 10 June 2008 (UTC) It seems to be a line floating in space. I understand what the "lens plane" is (a line through the lens), but not what the "lens object focal plane" is.

Any definition I would give would be essentially the same as that in the linked article focal plane. Is the confusion between "object focal plane" and "front focal plane"? JeffConrad (talk) 07:28, 10 June 2008 (UTC)

Yes, that's my confusion. RobertSeber (talk) 07:59, 10 June 2008 (UTC)

The diagram and the article do use the same terminology; the diagram is just missing a couple of symbols :-). It's easier to add an equation and a sentence than it is to update a diagram, but having the symbols on the diagram seems reasonable, so I'll try to get them added. JeffConrad (talk) 22:21, 9 June 2008 (UTC)

Lensbaby

I've cleaned up the description of the Lensbaby SLR lens, but wonder if its mention here is appropriate. Although the Lensbaby has become fairly popular for creative selective focus, the effect it achieves is only marginally related to the Scheimpflug principle discussed in this article. It seems particularly strange to give it almost as much space as is given to view camera movements and tilt/shift lenses combined; however, I think mention in this context without some qualification would be very misleading. JeffConrad (talk) 21:25, 14 April 2008 (UTC)

I've put the Lensbaby material in the article Tilt-shift photography, for which I think it's more appropriate. To avoid unnecessary duplication, I think we should remove that material from this article, and will do so if no one objects. JeffConrad (talk) 08:51, 10 July 2008 (UTC)

Links to equipment manufacturers

I removed the link to the Arri tilt/shift bellows system because this article is about the Scheimpflug principle rather than the equipment. If the consensus is that we should include equipment links, then we should treat manufacturers equally by providing links to all. In the interim, I'll add the Arri link to the Perspective correction lens article. JeffConrad (talk) 21:46, 26 July 2008 (UTC)

Adjusting focus

Unclear: "When the lens and image planes are not parallel, adjusting focus..." what kind of movement of the lens adjusts focus, moving it back and forth along the axis perpendicular to the lens plane? Please clarify or link to appropriate article.

Thanks,

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--- —Preceding unsigned comment added by 99.226.153.169 (talk) 16:09, 30 July 2008 (UTC)

Focus is adjusted by changing the distance between the lens and image planes (specifically, the distance v′ in the text and in Figure 4), in the same manner as is normally done for a particular camera. On a view camera, focus is usually adjusted by moving the rear standard or camera back; it can also be done by moving the front standard. In either case, the motion usually isn't parallel to the axis of a tilted lens. On small-and medium-format cameras, focus is usually adjusted by moving the lens along its axis. It's possible to focus by moving the entire camera, as sometimes is done with small- and medium-format cameras in closeup work; this does not change the angle of the PoF, but it's by far the exception rather than the rule.

Strictly, the PoF rotation axis remains fixed only when focus is adjusted by moving the camera back. With a tilt/shift lens or adapter on a small- or medium-format camera, focusing is accomplished by moving the lens rather than the camera back, so the rotation axis moves slightly with focus. However, except for extreme closeups, the difference is usually insignificant. When the tilt is between the camera and the focusing mechanism (as on all current tilt/shift lenses), the focusing motion is at a slight angle to the line of sight, and there is a slight vertical motion as well as a change in v′, but again, the slight movement of the rotation axis is usually insignificant. JeffConrad (talk) 23:31, 30 July 2008 (UTC)

Scheimpflug and ophthalmology

I've made a quick cleanup of the lead section, but it probably could use further improvement and generalization. It might also help to have an entire section on this topic. JeffConrad (talk) 23:03, 3 May 2009 (UTC)

Key points of the Scheimpflug principle

This comment on 15 March 2010 mistakenly addressed both JayWarner's comment of February 2007 and Cjrlord's comment of 15 March 2010. The article has changed considerably since Jay's comment was made, but perhaps it's appropriate to now ask whether the article makes the following points clear, so I've moved it to a new section.

The practical implications of the Scheimpflug principle are fairly simple:

1. Tilting the lens plane rotates the plane of focus away from parallel to the image plane.
2. The distance to the axis of rotation is controlled by the tilt, and the angle of the plane of focus is controlled by the focus (i.e., lens-to-film distance).
3. The DoF is wedge shaped when the lens is tilted.
4. The angular DoF (i.e., the angle at the apex of the DoF wedge) is controlled by the lens f-number.
5. The DoF on plane parallel to the image plane is the same on each side of the plane of focus.

These points apply to swing as well as tilt, and also apply to these movements on the camera back.

Does the article clearly convey this, or are these points buried in the details? It seems to me that item 4 is more implied than stated. Should the article include a summary similar to this? JeffConrad (talk) 14:19, 16 March 2010 (UTC)