From: Neil Harrington on

"bugbear" <bugbear(a)trim_papermule.co.uk_trim> wrote in message
news:1KOdnRFZo9HplfzRnZ2dnUVZ7vWqnZ2d(a)brightview.co.uk...
> Neil Harrington wrote:
>
>> 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.
>
> I suggest you look up the term "parallax" and consider
> its implications before continuing.

I'm very familiar with the principle of parallax but am not sure what
relevance you are attaching to it here.


From: Neil Harrington on

"Mike Warren" <miwa-not-this-bit(a)or-this-csas.net.au> wrote in message
news:xn0gxprtj84ue1005(a)news.aioe.org...
> 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.

I think it is, but admittedly haven't taken any polls. :-)

> 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.

Yes. Not only difference in apparent size, but also in shapes and angles.
For example, there is the familiar ultrawide-angle "distortion" of people's
heads making them appear egg-shaped when near the edge(s) of the frame.
("Distortion" in quotes because it isn't really a distortion at all, but
only a matter of the viewer's eye being in the wrong place for seeing the
picture in correct perspective.) That is really just another example of
wide-angle perspective.

>
> 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.

I understand what you mean and agree that that, too, is a matter of
perspective. But perspective is more than just that.


From: Peter on
"Savageduck" <savageduck1@{REMOVESPAM}me.com> wrote in message
news:2010080818434227544-savageduck1(a)REMOVESPAMmecom...

>
> Damn! I should have thought of doing that.
>
> So it seems the eye is easily fooled by focal length changes. Thanks for
> the proof you provided, I kind of takes the wind out of my sails, but
> there it is.
>

The concept of WA perspective is confused with slight changes in the
alignment of the focal plane to the subject. You can change the perspective
by simply changing that alignment. With a WA lens the change is more readily
apparent because it is closer to the subject. You can get a similar effect
using a PC lens or a view camera with a shift-tilt back.


--
Peter

From: Neil Harrington on

"Shiva Das" <shiv(a)nataraja.invalid> wrote in message
news:shiv-663310.19271109082010(a)reserved-multicast-range-NOT-delegated.example.com...
> 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

I don't. I also don't read Italian, which is what that text appears to be
in. But in any case, the illustration in that article is of a camera
obscura. (With a "b.")

>
>
> 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.

You are probably wise to do so. You might want to instead spend the time
brushing up on the difference between Latin and Italian.


From: Neil Harrington on

"bugbear" <bugbear(a)trim_papermule.co.uk_trim> wrote in message
news:1KOdnRBZo9FzlfzRnZ2dnUVZ7vU3AAAA(a)brightview.co.uk...
> Neil Harrington wrote:
>> "Shiva Das" <shiv(a)nataraja.invalid> wrote in message
>
>>> <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.
>
> OK. Would you please define, as clearly, carefully and explicitly
> as you can, what you mean by "perspective"

<groan>

If we're going to start getting into arguments about lengthy definitions of
rather ordinary terms, this will have to wait until I get back as I'm going
out of state in a little while.

But briefly, in the sense we are using the term here, perspective is the
rendering on a two-dimensional surface of the shapes and apparent
relationship of objects (or parts of a single object) in a three-dimensional
world.

>
> For extra merit, try to avoid circular logic.

That is to be expected and required, and should not be given extra merit.