Talk:Perspective (graphical)

From Wikipedia, the free encyclopedia

This article falls within the scope of WikiProject Visual arts, an attempt to build a comprehensive and detailed guide to visual arts on Wikipedia. If you would like to participate, visit the project page, where you can join the project and/or contribute to the discussion.
??? Class: This article has not been assigned a class according to the assessment scale.

Contents


"An exact replication of the image perceived by the eye is only possible when the picture plane is a spherical surface or portion of a spherical surface (with the center of the sphere located at the observer's eye). The distortion that occurs is similar to the distortions that occur when attempting to represent the globe (approximately spherical) on a flat surface (see perspective projection distortion)."

This is simply untrue (see my comment also under 'Perspective projection distortion'). There seems to me to be much confusion arising from the notion that perspective in some way emulates the behaviour of the retina. It doesn't: it allows a canvas (screen, etc) to emulate a window on the world, when viewed from a given point (and if you move your viewpoint with respect to the canvas, the correct perspective will be a different linear perspective, not a queer 'spherical' one.

Whereas the subject per force narrows the usage of the word Perspective from the subjective to eye/photo-visualization,

And whereas, in doing so, it per force addresses the technological aspects of eye/photo perspective,

And whereas the explanation of this technology derives from the phenomenon of graphical Projection,

It is hereby suggested that this page title be changed from Perspective (graphical) to Projective Perspective.

You may wish to write an article about Projective Perspective, but the question is exactly as it is stated: how to achieve the illusion of real world by graphical means: drawing, painting, photography. And please don't delete someone else's writing, especially if you offer no replacement to the introduced terms and discussed issues. Mikkalai 07:56, 8 Feb 2004 (UTC)

Apologies for the deletions….still a bit clumsy with protocols in Wiki….mea culpa.

I didn't think much about the scope of the article; I merely spawned it from the chaotic Perspective article. Of course, there are quite a few valid separate articles that can be created: --Pat 18:52, 21 Feb 2004 (UTC)

  • perspective in technical drawing,
  • in painting,
  • in photography,
  • in computer imaging,
  • in psychology of vision.

Big job still to be done. Mikkalai 20:57, 9 Feb 2004 (UTC)

A better caption to Pietro Perugino's fresco than my fatuous one, anybody? Wetman 18:32, 13 Aug 2004 (UTC)

_________________________________________

The author of the Perspective article seems to associate the word with "Opinion", among other categories, and proceeds to address a number of subjects of which there is no end. Before he advances to that point the author makes the statement:

[In Visual arts and mathematics the word perspective is used in a technical sense to denote a way of representing three-dimensional objects in the plane (of painting, photoimage, drawing) aimed at proper rendering of depth relationships, see perspective as graphical representation.

From that statement one might advantageously narrow one’s attention to Perspective as a Graphical Representation or, as the title was apparently changed to, Perspective (graphical). Under that title, it is suggested that a preferred approach is to explain (the source of?) Perspective (graphical) phenomenon and leave technical how-tos and applications, say to painting, religious icons, etc., to others specializing in those areas. Pat Kelso

____________________________________________

"In most modern drawings/paintings the linear perspective is used: the further the objects are from the viewer, the smaller they are drawn and the closer they are positioned to the so-called vanishing point or points, so that the (drawing of the) most remote objects completely disappear in the vicinity of these points.
"Under the linear perspective the vanishing point or points are usually placed inside the painting with the illusion that it is "beyond" the drawing.
"Under the reversed perspective, or inverse perspective, or Byzantine perspective the further the objects, the larger they are drawn. (The latter name is because thes kind of perspective is observed in earlier Byzantine and Russian Orthodox icons.) Technically, the vanishing points are placed outside the painting with the illusion that they are "in front of" the painting."

‘Having difficulty with the above. E.g.,

The phrase “linear perspective” most commonly distinguishes between perspective in imaging and other perspectives as perspective in thought (opinion).

 - the "linear" in linear perspective
   refers to the fact that more distant
   objects diminish in size in a
   linear fashion (if you graph the
   drawn size of a 1-foot object vs.
   the distance from the viewer, the
   points will align into a line)
 - although I have never personally
   seen a non-linear perspective,
   it is possible to do so (for
   example, the points in the graph
   mentioned above could form a
   parabola)


“…the smaller they are drawn and the closer they are positioned to the so-called vanishing point or points, so that the (drawing of the) most remote objects completely disappear in the vicinity of these points.”

The closer the that object appears to the horizon line (not, vanishing points) in space the smaller the drawing of the object will appear. The nearness of the object to the horizon line within the frame of the picture has no bearing on it size. Many objects frequently crossover the horizon line within the frame of the picture without effect to their sizes.

"Under the linear perspective the vanishing point or points are usually placed inside the painting with the illusion that it is ‘beyond’ the drawing.”

Don’t follow. Please explain use of “inside” and “beyond”.

"Under the reversed perspective, or inverse perspective, or Byzantine perspective the further the objects, the larger they are drawn. (The latter name is because thes kind of perspective is observed in earlier Byzantine and Russian Orthodox icons.)

I have misgivings that reverse, inverse and Byzantine perspective needs be addressed under ‘linear perspective’. Sizes in these seem more a matter of emphasis than trying for an illusion of depth. Reverse Perspective is often the term used to describe the condition wherein the station-point is located between the picture plane and the object of projection.

“Technically, the vanishing points are placed outside the painting with the illusion that they are "in front of" the painting.”

Don’t follow again. Please explain use of “outside” and “in front of”.

Please forgive my opaqueness. Pat Kelso

______________________

deleted: "Axonometric perspective is in between the two others: the relative sizes of depicted objects do not depend on the distance to the actual ones."

Note Axonometric is a form of Orthographic Projection. Pat 18:52, 21 Feb 2004 (UTC)


The follosing piece is cut out of Perspective

Perspective can be drawn in an instinctive way (as in the visual fine arts such as painting, sketching, etching, etc.) as well as in a quantified, technical way (technical graphics using drafting instruments).
It is widely held that perspective as a means of graphic representation was discovered by Brunelleschi during the Renaissance period. However, it is likely that other civilsations knew the technique, for example, there is a particular painting in the Ajanta caves in India that employs a similar method.

IMO it must be incorporated into this artice.Mikkalai 20:41, 21 Feb 2004 (UTC)


______________________

...Don’ t quite follow …….. are you saying to restore the cutout above?

From Perspective projection distortion re Brunelleschi:

The physiological basis of foreshortening went undefined until the year 1000 when the Arabian mathematician and philosopher, Alhazen, in his Perspectiva, first explained that light projects conically into the eye. A method for presenting foreshortened geometry systematically on a plane surface was unknown for another 300 years. The artist Giotto may have been the first to recognize that the image beheld by the eye is distorted---that to the eye, parallel lines appear to intersect (in the manner of receding railroad tracks) whereas in "undistorted" nature, they do not.

From other sources:

One of the first uses of perspective was in Giotto’s ‘Jesus Before the Caïf’, more that 100 years before Brunelleschi’s perspectival demonstrations galvanized the widespread use of convergent perspective of the Renaissance proper.

I suggest a confusion factor in the past discussions of perspective is distinguishing between ‘foreshortening’ and ‘perspective projection’. Note that both words are needed: all ‘foreshortening’ is not perspective projection but all ‘perspective projection’ is ‘foreshortening’. Artists use both, generalized 'foreshortening' often intuitively, specialized 'perspective projection', mechanically. The technically trained usually use the later except when sketching. As you noted 'foreshortening' but not 'perspective projection' is found on Indian caves. I suggest that Wiki consider narrowing its use of the term ‘perspective’, as it relates to visual matters, to ‘perspective projection’. Accordingly suggest Perspective (graphical) be moved to Perspective projection. Or better still, create a new catagory of, say, 'Visual arts foreshortening' under which all perspective subjects and presumably, also photography would appear.

Pat Kelso 01:07, Mar 20, 2004 (UTC)

I'm a newbie here at Wikipedia, and I don't wish to burst into the midst of the tea party, but I've seen no mention at all of atmospheric perspective. BillHealey 22:45, Oct 16, 2004 (UTC)

[edit] Merge

I've just merged all the information from Linear perspective in to Perspective (graphical). It's a real mess right now, but I'll be cleaning it up over the next few days. I'm also going to be re-writing a lot of the information so it's actaully understandable to a unexperienced person. Since no one has touched either article in a year, I hope no one will mind. Zhatt 22:51, 13 October 2005 (UTC)

I made linear perspective redirect here, rather then have the same information on two pages. Tried to clean up the whole One-point et cetera sections. There is certainly no reason to have the information on another page, when it works well as part of the general perspective page. Sir Isaac Lime 14:19, 5 March 2006 (UTC)

[edit] Van Eyck

The article references Van Eyck, but it doesn't say which one. Wikipedia already has two, and both painters, so which one is it? The name should also be a link. -Volfy 04:11, 26 October 2005 (UTC)

Nevermind, fixed it -Volfy 04:16, 26 October 2005 (UTC)

[edit] Cleanup Tag

I added a cleanup tag to this article as it's not following the manual of style in some areas and it's not really telling the reader what perspective is. It talks a lot about where it comes from, how to make it and why it works, but not what it is.

I've been drawing for some time now, and one of my favorite things to do is a strong perspective, but I don't understand half of what's being said in this article. The average person should be able to read this article and have a good understanding of the concept of perspective. I mean, there's barely even mention of the horizon in this article!

I also recreated the linear perspective article as all the content that was once that article has been edited out of this one.

A lot of work needs to be done on these articles. Maybe I'll be able to start on some of it later.

Zhatt 20:01, 8 February 2006 (UTC)

Sorry, a lot of the content that I thought was edited out was, in fact, and old vandal. I reverted, but there's still a lot to be done. Zhatt 20:17, 8 February 2006 (UTC)
I've removed the tag - it looks to me like these issues have been addressed. --OpenToppedBus - Talk to the driver 13:42, 18 April 2006 (UTC)

[edit] variscalar

Removed the following text:

freehand sketching aided by instruments.A photograph automatically shows a scene with correct perspective for the location of the camera. It follows that an artist wishing tp paint a picture of the scene with true perspective needs only to draw an accurate copy of the photograph. If his painting is to be of a different size from that of the photograph he must accurately scale it up or down. This may easily be done by using a Proportional Divider, sometimes called a Variscaler, set to give the scaling ratio which is required to fit the scene on to his painting support

As I see it, the problems are:

  • A photograph is not technically correct perspective, it is simply what looks most correct to us. A photograph is technically spherically warped (as can bee seen when multiple photos are put together to make a larger picture.)
  • It is not technically constructing perspective, it is simply copying a previous perspective construction. In the same vein, a xerox machine could be listed if you use it to make copies of a perspective drawing.

I moved it to its own item (cut down), but even that may be unnecessary. Sir Isaac Lime 21:39, 22 April 2006 (UTC)

[edit] Merge (Perspective Projection)

(copied this over from Talk:Perspective_projection after merging --Allefant 19:29, 7 July 2007 (UTC))

Perspective projection and Perspective (graphical) seem to basically be about the same subject, I think they should be merged (i.e. take what contents is useful from the shorter one and work into the longer one), and decide which name to keep. I also did some literature search and fixed some factual errors with proper references in some of the smaller projection pages (i.e. linked from that views template) recently, so likely there's also still mistakes in the bigger articles (perspective and orthographic projection) - hopefully this can all be cleaned up eventually. --Allefant 20:36, 4 July 2007 (UTC)

Agreed. I think the [Perspective projection]] should probably just be merged & redirected into Perspective (graphical), just as linear perspective was. They all discuss the exact same thing. The "projection" template actually seems to be the main thing that Perspective projection has that Perspective (graphical) does not. The template, however, seems less important than the information that is already at the head of the article (the diagram of perspective & the table of contents). Perhaps it should be slipped into the "basic concept" section?Sir Isaac Lime 14:47, 5 July 2007 (UTC)
Yes, I think there's actually no information in the current Perspective projection text which is not already here, also the figure doesn't seem to fit the paragraph besides it. The list of concepts likely isn't that useful either as they are already used in the article (I think they all are), and that external spanish link should go away anyway. So the merge should be rather trivial. Whether or not Template:Views is really needed is another question - I'd just place it on Perspective (graphical) initially, and if it's not liked, maybe it should eventually be phased out from all articles who currently have it. --Allefant 15:21, 5 July 2007 (UTC)

Ok, I merged it now, and did not keep any contents. --Allefant 19:29, 7 July 2007 (UTC)

[edit] External links

I removed most of the external links. World of Escher is a commercial site that sells posters or something, two other links had only Spanish text. In general I see little point in putting examples of various types of perspective into the external links. If more illustrations would be helpful, they should be taken from free images and integrated into the article.—Graf Bobby 16:35, 23 July 2007 (UTC)

[edit] Foreshortening

This section is a little bit unclear. The image could use an example of a projection where foreshortening does not occur. SharkD (talk) 02:11, 21 December 2007 (UTC)

[edit] Roman Perspective

I believe the historical section jumps too quickly from classic Greece to the Middle Ages. There are several examples of Roman frescoes with excellent one point perspective: http://www.didaskalia.net/studyarea/visual_resources/rometemp3d.html Others can be found with a search for Skenographia or house of Augustus.

I have tested sight lines on a couple, and they demonstrate that the Romans had a fine understanding that the lines should meet at one point at eyelevel.

Carpets (talk) 14:26, 26 January 2008 (UTC)

It would be great to have more info on Roman perspective. Are there any articles you can find that discuss Roman perspective?Sir Isaac Lime (talk) 15:12, 26 January 2008 (UTC)

Not really, but here are links to one page each of three articles on the subject:

http://links.jstor.org/sici?sici=0075-4269(1999)119%3C161%3AVVOTSO%3E2.0.CO%3B2-O http://links.jstor.org/sici?sici=0002-9114(197210)76%3A4%3C454%3ARPPATA%3E2.0.CO%3B2-9 http://links.jstor.org/sici?sici=0002-9114(194504%2F06)49%3A2%3C134%3ATFOARS%3E2.0.CO%3B2-B

Alan M.G.Little seems to be the „expert“ on the subject. Here is a blurb about his book:

http://209.85.135.104/search?q=cache:DW2N1hfmz30J:www.jenniferreut.com/ppsite/perspace.htm+roman+perspective&hl=en&ct=clnk&cd=21

This is all the following site says about Vitruvius: http://www.dartmouth.edu/~matc/math5.geometry/unit11/unit11.html

“Vitruvius' Ten Books on Architecture which appeared about 25 B.C., was the only book on architecture to survive from antiquity. It profoundly influenced Renaissance architecture and thinking, including that of Alberti, who quoted Vitruvius in his Della pittura. Vitruvius wrote, Perspective is the method of sketching a front with the sides withdrawing into the background, the lines all meeting in the center of a circle. Unfortunately he didn't elaborate on that. Elsehere, Vitruvius' reference to Greek and Roman stage design, implied an understanding of the vanishing point.” That is from the 2nd chapter of his first book: http://www.lih.gre.ac.uk/histhe/vitruvius.htm From the Roman frescoes, Vitruvius only explained in one sentence what the artists already understood and practiced. No, I don’t want to edit the article, so anyone who agrees please do so. Carpets (talk) 13:36, 27 January 2008 (UTC)