Perspective (was Re: Has ultrawide angle become an overused cliche?)
in [Digital Cameras]
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From: David Ruether on 9 Aug 2010 16:53 "Bruce" <docnews2011(a)gmail.com> wrote in message news:74o06692o0kh4bf29glsnj8lvno7guev9l(a)4ax.com... > On Mon, 9 Aug 2010 12:23:08 -0400, "David Ruether" > <d_ruether(a)thotmail.com> wrote: >>Ah, the above reminds me of my teaching days.......! ;-) I found it >>easy using a blackboard and chalk, drawing a "lens", a "stick figure", >>and a "film plane" to show the effects of keeping FL constant, changing >>FL, keeping the film plane constant in size relative to the FL or changing >>that, and the effect of changing the lens opening size on an out of focus >>image on the film plane using drawn sections of "cones" of light... >>Fun! > It is fun, especially if you have a receptive audience. But it takes > only one Neil Harrington to spoil the party. ;-) 8^) >>(But the most fun was getting people to "see" that they don't see >>straight lines off the center of their vision that are strait in the subjects >>they look at - in other words, we don't see in rectangular perspective...;-) > It's fascinating how the eye and brain work together. The eye "sees" > like a fisheye lens, but the brain corrects it to rectilinear. It is > rather like the Nikon 10.5mm fisheye, with software "correcting" the > results to rectilinear ... ;-) Ah, but the brain *doesn't* correct it to rectilinear perspective! THAT'S what's so much fun to show people (that the way they think they see isn't the way they really do see...;-). There are simple exercises that permit people to attend to their off-center field of vision, and once that is accomplished, it is easy to see under some conditions of high color or tone contrast the clear curvatures of the fisheye perspective type. Also, logically there can be no 180-degree rectangular perspective image (the image plane would be infinitely large, and the "lens" FL would be zero), although we do see slightly more than 180 degrees horizontally, so there cannot be anything near a 180-degree fisheye-to-rectangular perspective conversion. For more, with an image approximation of how we do see, go here -- http://www.donferrario.com/ruether/seeing_and_perspective.htm (There are more articles on perspective, here -- http://www.donferrario.com/ruether/articles.html .) --David Ruether www.donferrario.com/ruether d_ruether....@....hotmail.com
From: Shiva Das on 9 Aug 2010 17:26 In article <3vGdnRvgvJ9_q_3RnZ2dnUVZ_oudnZ2d(a)giganews.com>, "Neil Harrington" <nobody(a)homehere.net> wrote: > "Shiva Das" <shiv(a)nataraja.invalid> wrote in message > news:shiv-BDD52B.12332709082010(a)reserved-multicast-range-NOT-delegated.example > .com... > > In article <2010080817520211272-savageduck1(a)REMOVESPAMmecom>, > > Savageduck <savageduck1@{REMOVESPAM}me.com> wrote: > > > >> On 2010-08-08 16:37:50 -0700, Bruce <docnews2011(a)gmail.com> said: > >> > >> > On Sun, 8 Aug 2010 16:43:55 -0400, "Neil Harrington" > >> > <nobody(a)homehere.net> wrote: > >> >> "Bruce" <docnews2011(a)gmail.com> wrote in message > >> >> news:ugar46dfhpou4nimibd86jm53iqo459f99(a)4ax.com... > >> >>> On Mon, 26 Jul 2010 09:54:10 -0400, Shiva Das <shiv(a)nataraja.invalid> > >> >>> wrote: > >> >>>> In article <5k2r46pe2t2t7tsjn802pa3o5v7lla946f(a)4ax.com>, > >> >>>> Bruce <docnews2011(a)gmail.com> wrote: > >> >>>>> It also doesn't help when people associate perspective with the > >> >>>>> lens's > >> >>>>> focal length. Perspective is purely a function of viewpoint and > >> >>>>> its > >> >>>>> relationship with the subject. The focal length of the lens is > >> >>>>> irrelevant. > >> >>>> > >> >>>> In "Photographic Lenses: Photographer's Guide to Characteristics, > >> >>>> Quality, Use and Design" Ernst Wildi has two sets of photographs > >> >>>> using > >> >>>> progressively longer lenses from 38mm to 500mm Hasselblad lenses > >> >>>> (20mm > >> >>>> to 255mm equivalentin 35mm film format). > >> >>>> > >> >>>> The first sequence, one shot per lens, is taken standing in the same > >> >>>> spot looking at the same scene. The second sequence is of a lovely > >> >>>> lady > >> >>>> on the beach and he moved the camera to keep her the same size in > >> >>>> each > >> >>>> image. > >> >>>> > >> >>>> It does a great job of showing how focal length and distance affect > >> >>>> perspective. > >> >>> > >> >>> > >> >>> Yes, that is the classic method of demonstrating that perspective is > >> >>> independent of focal length. > >> >>> > >> >>> It is to be found in many books on photography, yet people still keep > >> >>> making the same mistake over and over again, thinking that > >> >>> perspective > >> >>> is dependent on focal length. > >> >> > >> >> But perspective *is* largely dependent on focal length. > >> >> > >> >> The the other poster mentioned ". . . how focal length and distance > >> >> affect > >> >> perspective." > >> >> > >> >> Focal length is not "irrelevant." Both are important: focal length > >> >> *and* > >> >> camera position. A shot taken with a wide-angle lens has wide-angle > >> >> perspective, which (assuming there are enough objects arranged in the > >> >> scene > >> >> to establish perspective at all) is easily recognized by anyone > >> >> looking at > >> >> the resulting photo. To say that focal length is irrelevant is to deny > >> >> what > >> >> anyone can see with his own eyes. > >> >> > >> >> (Sorry for being more than a week late in replying to this, but I only > >> >> saw > >> >> the thread just now. The misunderstanding is important enough to > >> >> correct. > >> >> The "many books" that support the idea are mistaken, as are the > >> >> several > >> >> people who have repeated it over the years.) > >> > > >> > > >> > The "misunderstanding" is entirely yours, Neil. It is a very common > >> > misunderstanding. However, it doesn't matter how many people repeat > >> > it, nor how many times, it is still wrong. There is no such thing as > >> > "wide angle perspective". > >> > > >> > Perspective is purely a function of viewpoint and its relationship > >> > with the subject. The focal length of the lens is irrelevant. > >> > > >> > >> OK. > >> I tried the following; > >> D300s on tripod 2 shots, position of tripod unchanged, aim point > >> unchanged, distance between camera and subject constant, lenses > >> changed, EXIF included; > >> > >> Shot #1 Tokina 11-16mm f/2.8 @ 11mm (16mm FF equiv.) > >> < http://homepage.mac.com/lco/filechute/_DNC3876w.jpg > > >> > >> Shot #2 Nikkor 16-200mm VRII @ 35mm (52mm FF equiv.) > >> < http://homepage.mac.com/lco/filechute/_DNC3877w.jpg > > >> > >> Side by-side comparison; > >> < http://homepage.mac.com/lco/filechute/Merc-comp-01.jpg > > >> > >> It is tough to say that that this is not a demonstration of focal > >> length perspective change. > >> The view point is constant, the relationship between the subject (the > >> car) and the camera remains unchanged. Yet the eye tells the viewer > >> there is a dramatic change in perspective, in this case created > >> entirely by a change of focal length. > > > > Nope. > > > > <http://www.flickr.com/photos/52865695(a)N03/4875633691/> > > > > All I did was crop the 11mm photo to the same field of view as the 35mm > > photo. There is absolutely no difference in the perspective. > > Cropping the photo changes its perspective. How? Vanishing point angle and location: the same Angle of view: the same Sensor to subject distance: the same Perspective: the same. And by perspective I mean what Albrecht Durer, Johannes Vermeer, Leonardo da Vinci, and Michelangelo Buonarote meant by perspective: the geometrical reconstruction of a stationary point of view looking at an image projected on a stationary picture plane (in the case of Durer a glass plate, in the case of Vermeer a Camera Oscura). _Move_ any of these components and you change the perspective. _Change_ the magnification -- changing the size of the picture plane, using a different focal length lens -- and you have _not_ changed the perspective. The whole point of cropping the wide angle shot is to show that the geometric perspective is identical. Are you saying that if I hadn't cropped the wide angle shot that suddenly its vanishing point(s) would _move_? That the distance to the subject would _move_? That the geometric ratios of the various parts of the picture would _move_? Perhaps the car's tires would suddenly become square?
From: Neil Harrington on 9 Aug 2010 18:15 "Shiva Das" <shiv(a)nataraja.invalid> wrote in message news:shiv-ED74C2.17262909082010(a)reserved-multicast-range-NOT-delegated.example.com... > In article <3vGdnRvgvJ9_q_3RnZ2dnUVZ_oudnZ2d(a)giganews.com>, > "Neil Harrington" <nobody(a)homehere.net> wrote: > >> "Shiva Das" <shiv(a)nataraja.invalid> wrote in message >> news:shiv-BDD52B.12332709082010(a)reserved-multicast-range-NOT-delegated.example >> .com... >> > In article <2010080817520211272-savageduck1(a)REMOVESPAMmecom>, >> > Savageduck <savageduck1@{REMOVESPAM}me.com> wrote: >> > >> >> On 2010-08-08 16:37:50 -0700, Bruce <docnews2011(a)gmail.com> said: >> >> >> >> > On Sun, 8 Aug 2010 16:43:55 -0400, "Neil Harrington" >> >> > <nobody(a)homehere.net> wrote: >> >> >> "Bruce" <docnews2011(a)gmail.com> wrote in message >> >> >> news:ugar46dfhpou4nimibd86jm53iqo459f99(a)4ax.com... >> >> >>> On Mon, 26 Jul 2010 09:54:10 -0400, Shiva Das >> >> >>> <shiv(a)nataraja.invalid> >> >> >>> wrote: >> >> >>>> In article <5k2r46pe2t2t7tsjn802pa3o5v7lla946f(a)4ax.com>, >> >> >>>> Bruce <docnews2011(a)gmail.com> wrote: >> >> >>>>> It also doesn't help when people associate perspective with the >> >> >>>>> lens's >> >> >>>>> focal length. Perspective is purely a function of viewpoint and >> >> >>>>> its >> >> >>>>> relationship with the subject. The focal length of the lens is >> >> >>>>> irrelevant. >> >> >>>> >> >> >>>> In "Photographic Lenses: Photographer's Guide to Characteristics, >> >> >>>> Quality, Use and Design" Ernst Wildi has two sets of photographs >> >> >>>> using >> >> >>>> progressively longer lenses from 38mm to 500mm Hasselblad lenses >> >> >>>> (20mm >> >> >>>> to 255mm equivalentin 35mm film format). >> >> >>>> >> >> >>>> The first sequence, one shot per lens, is taken standing in the >> >> >>>> same >> >> >>>> spot looking at the same scene. The second sequence is of a >> >> >>>> lovely >> >> >>>> lady >> >> >>>> on the beach and he moved the camera to keep her the same size in >> >> >>>> each >> >> >>>> image. >> >> >>>> >> >> >>>> It does a great job of showing how focal length and distance >> >> >>>> affect >> >> >>>> perspective. >> >> >>> >> >> >>> >> >> >>> Yes, that is the classic method of demonstrating that perspective >> >> >>> is >> >> >>> independent of focal length. >> >> >>> >> >> >>> It is to be found in many books on photography, yet people still >> >> >>> keep >> >> >>> making the same mistake over and over again, thinking that >> >> >>> perspective >> >> >>> is dependent on focal length. >> >> >> >> >> >> But perspective *is* largely dependent on focal length. >> >> >> >> >> >> The the other poster mentioned ". . . how focal length and distance >> >> >> affect >> >> >> perspective." >> >> >> >> >> >> Focal length is not "irrelevant." Both are important: focal length >> >> >> *and* >> >> >> camera position. A shot taken with a wide-angle lens has wide-angle >> >> >> perspective, which (assuming there are enough objects arranged in >> >> >> the >> >> >> scene >> >> >> to establish perspective at all) is easily recognized by anyone >> >> >> looking at >> >> >> the resulting photo. To say that focal length is irrelevant is to >> >> >> deny >> >> >> what >> >> >> anyone can see with his own eyes. >> >> >> >> >> >> (Sorry for being more than a week late in replying to this, but I >> >> >> only >> >> >> saw >> >> >> the thread just now. The misunderstanding is important enough to >> >> >> correct. >> >> >> The "many books" that support the idea are mistaken, as are the >> >> >> several >> >> >> people who have repeated it over the years.) >> >> > >> >> > >> >> > The "misunderstanding" is entirely yours, Neil. It is a very common >> >> > misunderstanding. However, it doesn't matter how many people repeat >> >> > it, nor how many times, it is still wrong. There is no such thing >> >> > as >> >> > "wide angle perspective". >> >> > >> >> > Perspective is purely a function of viewpoint and its relationship >> >> > with the subject. The focal length of the lens is irrelevant. >> >> > >> >> >> >> OK. >> >> I tried the following; >> >> D300s on tripod 2 shots, position of tripod unchanged, aim point >> >> unchanged, distance between camera and subject constant, lenses >> >> changed, EXIF included; >> >> >> >> Shot #1 Tokina 11-16mm f/2.8 @ 11mm (16mm FF equiv.) >> >> < http://homepage.mac.com/lco/filechute/_DNC3876w.jpg > >> >> >> >> Shot #2 Nikkor 16-200mm VRII @ 35mm (52mm FF equiv.) >> >> < http://homepage.mac.com/lco/filechute/_DNC3877w.jpg > >> >> >> >> Side by-side comparison; >> >> < http://homepage.mac.com/lco/filechute/Merc-comp-01.jpg > >> >> >> >> It is tough to say that that this is not a demonstration of focal >> >> length perspective change. >> >> The view point is constant, the relationship between the subject (the >> >> car) and the camera remains unchanged. Yet the eye tells the viewer >> >> there is a dramatic change in perspective, in this case created >> >> entirely by a change of focal length. >> > >> > Nope. >> > >> > <http://www.flickr.com/photos/52865695(a)N03/4875633691/> >> > >> > All I did was crop the 11mm photo to the same field of view as the 35mm >> > photo. There is absolutely no difference in the perspective. >> >> Cropping the photo changes its perspective. > > How? > Vanishing point angle and location: the same What vanishing point? There is no obvious one in this photo. Of course you may put a virtual vanishing point anywhere you like, but that makes it irrelevant in this case. > Angle of view: the same Of course. And angle of view = effective focal length. That's what you've done by cropping the photo. > Sensor to subject distance: the same Yes, but irrelevant. > > Perspective: the same. Of course, since you've effectively made the focal length the same. Same viewpoint + same focal length = same perspective. But only in your cropped example, not in the original photos. > > And by perspective I mean what Albrecht Durer, Johannes Vermeer, > Leonardo da Vinci, and Michelangelo Buonarote meant by perspective: the > geometrical reconstruction of a stationary point of view looking at an > image projected on a stationary picture plane (in the case of Durer a > glass plate, in the case of Vermeer a Camera Oscura). Obscura, I assume you mean. Anyway, that's what I mean by perspective too. Change the focal length and (in most cases) you change important elements of all that, thus change the perspective. If any painter had used a camera obscura projecting a wider angle image, the perspective would have changed accordingly. > > _Move_ any of these components and you change the perspective. Exactly. And that includes angle of view. > > _Change_ the magnification -- changing the size of the picture plane, > using a different focal length lens -- and you have _not_ changed the > perspective. The whole point of cropping the wide angle shot is to show > that the geometric perspective is identical. Are you saying that if I > hadn't cropped the wide angle shot that suddenly its vanishing point(s) Again, WHAT vanishing point? > would _move_? That the distance to the subject would _move_? That the > geometric ratios of the various parts of the picture would _move_? No, I'm saying that if you hadn't cropped the wide angle shot you wouldn't have changed its perspective. The entire picture contributes to the perspective, not just a tiny part. Explained at length elsewhere and I'm not going over it all again. > > Perhaps the car's tires would suddenly become square? Well, if they had, that at least might have provided you with a vanishing point.
From: Shiva Das on 9 Aug 2010 19:27 In article <crednS_gOehk4P3RnZ2dnUVZ_g-dnZ2d(a)giganews.com>, "Neil Harrington" <nobody(a)homehere.net> wrote: > > > > And by perspective I mean what Albrecht Durer, Johannes Vermeer, > > Leonardo da Vinci, and Michelangelo Buonarote meant by perspective: the > > geometrical reconstruction of a stationary point of view looking at an > > image projected on a stationary picture plane (in the case of Durer a > > glass plate, in the case of Vermeer a Camera Oscura). > > Obscura, I assume you mean. > You may assume what you wish. I meant exactly what I said: Camera Oscura. Brush up on it here -- I hope you read Latin: http://www.uniurb.it/Filosofia/bibliografie/Spinoza/camera.htm And since you have amply demonstrated that you do not understand the first thing about perspective, I will bow out of this waste of time of a discussion.
From: Mike Warren on 9 Aug 2010 21:16
Neil Harrington wrote: >"Mike Warren" <miwa-not-this-bit(a)or-this-csas.net.au> wrote in message >news:xn0gxodio8omm800i(a)news.aioe.org... >>I just performed a simple resize of the second image and laid it on >>top of the first: >> >>http://www.mike-warren.net/play/savageduck.jpg >> >>Perspective is unchanged. > >Perspective *of the resized overlay part* is unchanged, of course. All you >have done by resizing is to shrink the long-lens shot so that it matches >the homologous part of the wide-angle shot. Likewise, you could crop and >expand the same part of the wide-angle shot and (disregarding loss of >definition) the perspective *of that part* would then match that of the >long-lens shot. > >But perspective is established by the picture in its entirety, not a small >part. It is not valid to take a small part of a picture and say that >establishes the perspective of the whole picture. > >Wide angle shots are very obviously different in perspective than long >lens shots. The former create the effect of spatial expansion and the >latter create spatial compression -- which anyone can see, and the reason >they can see it is because of the difference in perspective. I don't get into arguments on the Internet so this likely will my last post on this subject. Like most UseNet arguments, this one revolves around a minor difference in definition of a single word. Your definition of "perspective" is not the most widely held one. The pictures I merged from SavageDuck would have been even more obvious if he had included some of the trees in the background in the narrower angle shot. It's seems to me that you already know this and are simply using a different definition of the word "perspective". Perspective relates to the difference in the apparent size of objects at different distances from the observer. The effect is not linear. This can be demonstrated by using 2 identical objects at different distances from the camera and changing the focal length and distance from the closer object. If you (or anyone else here) really doesn't understand this, I would be happy to provide a detailed explanation with accompanying pictures. -- - Mike |