"Cropping/Zooming does not affect perspective" fallacy, distilled.

[Lee Jay]

"the art of drawing solid objects on a two-dimensional surface so as to give the right impression of their height, width, depth, and position in relation to each other when viewed from a particular point."

"the technique or process of representing on a plane or curved surface the spatial relation of objects as they might appear to the eye"

Note, "particular point" and "to the eye". Perspective is entirely fixed by the "particular point" of "the eye".

This "one point" and "two point" perspective thing in drawing has only to do with what objects are in the frame and if you choose some of them to be parallel or not (thus eliminating a vanishing point) and has nothing to do with the "perspective" we talk about with photography, which has nothing to do with what's in the frame and only to do with where the camera was located.

 

[dmartin92]

On the bus PC1 in Paris, down by Porte Dauphine, where Edith Piaf used to live many years ago, there is a street from where you can see the Eiffel Tower. I see it from the bus PC1 from time to time. The bus passes by this street.

I am always a bit surprised by how close the Eiffel Tower looks. The two sides of the street crop the Eiffel Tower in a narrow box, and it looks quite close.

Much closer than it really is.

There are no lenses or cameras cropping the Eiffel Tower, only the sides of the street.

And the Eiffel Tower looks quite close. Closer than it is.

 

[tko]

Before you disprove something make sure you understand the argument you are tying to disprove.

The reason for the confusion is simply that "perspective" has a different meaning in geometry vs. the one in art and graphics.

It might help if you'd define the two meaning, because I don't think many would agree with you. And the point you are addressing (word definitions) has nothing to do with the common photography argument.

Perspective:

1.) Projecting solid objects on a two-dimensional surface so as to give an impression of height, width, depth, and position in relation to each other when viewed from a particular point.

2. A particular attitude toward or way of regarding something.

Definition #2 certainly doesn't apply, that leaves #1 as the only working definition. In your example, nothing has changed in relation to each other, so there is no change in perspective.

So far we are batting 100% on TKO's theorem. Any post that has the word fallacy in the title is itself a fallacy.

 

[WunWegWunDarWun]

Before you disprove something make sure you understand the argument you are tying to disprove.

The reason for the confusion is simply that "perspective" has a different meaning in geometry vs. the one in art and graphics.

It might help if you'd define the two meaning, because I don't think many would agree with you. And the point you are addressing (word definitions) has nothing to do with the common photography argument.

Perspective:

1.) Projecting solid objects on a two-dimensional surface so as to give an impression of height, width, depth, and position in relation to each other when viewed from a particular point.

2. A particular attitude toward or way of regarding something.

Definition #2 certainly doesn't apply, that leaves #1 as the only working definition. In your example, nothing has changed in relation to each other, so there is no change in perspective.

See my thread with tkbslc about it as this is a good point and is the one that actually got me thinking on the subject at the time but if we adopt this defnition we have no excuse to not treat the field of view itself as an element of the scene and so preserving perspective would also mean preserving "height, width, depth, and position" in relation to the field of view - or in other words to preserve framing and composition.

So far we are batting 100% on TKO's theorem. Any post that has the word fallacy in the title is itself a fallacy.

Have you considered starting a thread about it ?

 

[Lee Jay]

See my thread with tkbslc about it as this is a good point and is the one that actually got me thinking on the subject at the time but if we adopt this defnition we have no excuse to not treat the field of view itself as an element of the scene and so preserving perspective would also mean preserving "height, width, depth, and position" in relation to the field of view - or in other words to preserve framing and composition.

That would mix two topics that can be separately changed - point of view (also called "perspective") and framing.

This example changes perspective without changing framing of the main subject:

https://www.dpreview.com/forums/post/41415412

--
Lee Jay

 

[J A C S]

How about posts with the fallacy repeated in the title?

 

[WunWegWunDarWun]

See my thread with tkbslc about it as this is a good point and is the one that actually got me thinking on the subject at the time but if we adopt this defnition we have no excuse to not treat the field of view itself as an element of the scene and so preserving perspective would also mean preserving "height, width, depth, and position" in relation to the field of view - or in other words to preserve framing and composition.

That would mix two topics that can be separately changed - point of view (also called "perspective") and framing.

This example changes perspective without changing framing of the main subject:

https://www.dpreview.com/forums/post/41415412

This is titled "interesting focal length demo" I thought that under canonical wisdom focal length does not change perspective since the camera does not change position or orientation which it doesn't appear to do in that gif.

 

[Lee Jay]

See my thread with tkbslc about it as this is a good point and is the one that actually got me thinking on the subject at the time but if we adopt this defnition we have no excuse to not treat the field of view itself as an element of the scene and so preserving perspective would also mean preserving "height, width, depth, and position" in relation to the field of view - or in other words to preserve framing and composition.

That would mix two topics that can be separately changed - point of view (also called "perspective") and framing.

This example changes perspective without changing framing of the main subject:

https://www.dpreview.com/forums/post/41415412

This is titled "interesting focal length demo" I thought that under canonical wisdom focal length does not change perspective since the camera does not change position or orientation which it doesn't appear to do in that gif.

You can't be serious.

The camera was moving like crazy and focal length was changing to keep the main subject framed the same.

 

[WunWegWunDarWun]

See my thread with tkbslc about it as this is a good point and is the one that actually got me thinking on the subject at the time but if we adopt this defnition we have no excuse to not treat the field of view itself as an element of the scene and so preserving perspective would also mean preserving "height, width, depth, and position" in relation to the field of view - or in other words to preserve framing and composition.

That would mix two topics that can be separately changed - point of view (also called "perspective") and framing.

This example changes perspective without changing framing of the main subject:

https://www.dpreview.com/forums/post/41415412

This is titled "interesting focal length demo" I thought that under canonical wisdom focal length does not change perspective since the camera does not change position or orientation which it doesn't appear to do in that gif.

You can't be serious.

The camera was moving like crazy and focal length was changing to keep the main subject framed the same.

Yeah I see this is explained in the thread, I'm still not sure how it's related to original point though, per my definition the framing is being changed as well - the only thing that remains invariant is the fact that there is a stone structure in the middle - but nothing about it shape, size or surrounding content.

 

[sybersitizen]

See that one point (one pixel) crop of the image above? Feel free to discuss the perspective.

 

[WunWegWunDarWun]

See my thread with tkbslc about it as this is a good point and is the one that actually got me thinking on the subject at the time but if we adopt this defnition we have no excuse to not treat the field of view itself as an element of the scene and so preserving perspective would also mean preserving "height, width, depth, and position" in relation to the field of view - or in other words to preserve framing and composition.

That would mix two topics that can be separately changed - point of view (also called "perspective") and framing.

This example changes perspective without changing framing of the main subject:

https://www.dpreview.com/forums/post/41415412

This is titled "interesting focal length demo" I thought that under canonical wisdom focal length does not change perspective since the camera does not change position or orientation which it doesn't appear to do in that gif.

You can't be serious.

The camera was moving like crazy and focal length was changing to keep the main subject framed the same.

Yeah I see this is explained in the thread, I'm still not sure how it's related to original point though, per my definition the framing is being changed as well - the only thing that remains invariant is the fact that there is a stone structure in the middle - but nothing about it shape, size or surrounding content.

Actually the framing changes per the conventional definition as well, what stays the same is only the frame-relative size of the face of the stone structure parallel to image plane.

 

[Lee Jay]

See my thread with tkbslc about it as this is a good point and is the one that actually got me thinking on the subject at the time but if we adopt this defnition we have no excuse to not treat the field of view itself as an element of the scene and so preserving perspective would also mean preserving "height, width, depth, and position" in relation to the field of view - or in other words to preserve framing and composition.

That would mix two topics that can be separately changed - point of view (also called "perspective") and framing.

This example changes perspective without changing framing of the main subject:

https://www.dpreview.com/forums/post/41415412

This is titled "interesting focal length demo" I thought that under canonical wisdom focal length does not change perspective since the camera does not change position or orientation which it doesn't appear to do in that gif.

You can't be serious.

The camera was moving like crazy and focal length was changing to keep the main subject framed the same.

Yeah I see this is explained in the thread, I'm still not sure how it's related to original point though, per my definition the framing is being changed as well - the only thing that remains invariant is the fact that there is a stone structure in the middle - but nothing about it shape, size or surrounding content.

The framing of the main subject is (almost) constant, but the point of view (the "perspective") changes and that changes the relative sizes of the foreground and background objects relative to the main subject.

 

[Lee Jay]

See my thread with tkbslc about it as this is a good point and is the one that actually got me thinking on the subject at the time but if we adopt this defnition we have no excuse to not treat the field of view itself as an element of the scene and so preserving perspective would also mean preserving "height, width, depth, and position" in relation to the field of view - or in other words to preserve framing and composition.

That would mix two topics that can be separately changed - point of view (also called "perspective") and framing.

This example changes perspective without changing framing of the main subject:

https://www.dpreview.com/forums/post/41415412

This is titled "interesting focal length demo" I thought that under canonical wisdom focal length does not change perspective since the camera does not change position or orientation which it doesn't appear to do in that gif.

You can't be serious.

The camera was moving like crazy and focal length was changing to keep the main subject framed the same.

Yeah I see this is explained in the thread, I'm still not sure how it's related to original point though, per my definition the framing is being changed as well - the only thing that remains invariant is the fact that there is a stone structure in the middle - but nothing about it shape, size or surrounding content.

Actually the framing changes per the conventional definition as well, what stays the same is only the frame-relative size of the face of the stone structure parallel to image plane.

Framing refers to the image plane, which is infinitely thin (which is what a "plane" is). the framing of all the foreground (in front of the image plane) and the background (behind the image plane) cannot remain constant if location changes and framing of the main subject stays the same.

 

[Lee Jay]

Here is an example of a two-point perspective image:

And here is a crop of it that makes for a one-point perspective image:

No, that's still two-point. I'll draw it for you if you don't see it.

The reason for the confusion is simply that "perspective" has a different meaning in geometry vs. the one in art and graphics.

When discussing perspective of photos 99% times we actually mean the later

Wrong. We never mean the one discussed in art and graphics.


--
Lee Jay

 

[WunWegWunDarWun]

See my thread with tkbslc about it as this is a good point and is the one that actually got me thinking on the subject at the time but if we adopt this defnition we have no excuse to not treat the field of view itself as an element of the scene and so preserving perspective would also mean preserving "height, width, depth, and position" in relation to the field of view - or in other words to preserve framing and composition.

That would mix two topics that can be separately changed - point of view (also called "perspective") and framing.

This example changes perspective without changing framing of the main subject:

https://www.dpreview.com/forums/post/41415412

This is titled "interesting focal length demo" I thought that under canonical wisdom focal length does not change perspective since the camera does not change position or orientation which it doesn't appear to do in that gif.

You can't be serious.

The camera was moving like crazy and focal length was changing to keep the main subject framed the same.

Yeah I see this is explained in the thread, I'm still not sure how it's related to original point though, per my definition the framing is being changed as well - the only thing that remains invariant is the fact that there is a stone structure in the middle - but nothing about it shape, size or surrounding content.

The framing of the main subject is (almost) constant, but the point of view (the "perspective") changes and that changes the relative sizes of the foreground and background objects relative to the main subject.

Well I'd describe it as framing that changes in lockstep with the perspective to preserve the size of the image-plane-parallel facing side of the subject but this doesn't essentially change anything.

 

[Gerry Winterbourne]

Here is an example of a two-point perspective image:

And here is a crop of it that makes for a one-point perspective image:

In those two photos above? No it does not. The objects, their angle, and their spacing are all the same size in relation to each other in both frames.

They can't be "all the same size in relation to each other in both frames" because one frame contains objects that the other doesn't - some of those objects define the leading lines that determine perspective type.

Here's a copy of your large picture with the cropped version overlaid. I had to adjust the pixel dimensions to make them match, so the two are very slightly mismatched for size.

However, as you see they are identical in their perspective - if they weren't you'd see a distinct difference in the shape of the building.

So whatever reasoning you try to apply (and, frankly, I think your reasoning is warped) the plain evidence is that you are mistaken in saying they have different perspective.

--
---
Gerry
___________________________________________
First camera 1953, first Pentax 1985, first DSLR 2006

Galleries by Gerry Winterbourne

www.pbase.com

[email protected]

 

[WunWegWunDarWun]

See my thread with tkbslc about it as this is a good point and is the one that actually got me thinking on the subject at the time but if we adopt this defnition we have no excuse to not treat the field of view itself as an element of the scene and so preserving perspective would also mean preserving "height, width, depth, and position" in relation to the field of view - or in other words to preserve framing and composition.

That would mix two topics that can be separately changed - point of view (also called "perspective") and framing.

This example changes perspective without changing framing of the main subject:

https://www.dpreview.com/forums/post/41415412

This is titled "interesting focal length demo" I thought that under canonical wisdom focal length does not change perspective since the camera does not change position or orientation which it doesn't appear to do in that gif.

You can't be serious.

The camera was moving like crazy and focal length was changing to keep the main subject framed the same.

Yeah I see this is explained in the thread, I'm still not sure how it's related to original point though, per my definition the framing is being changed as well - the only thing that remains invariant is the fact that there is a stone structure in the middle - but nothing about it shape, size or surrounding content.

Actually the framing changes per the conventional definition as well, what stays the same is only the frame-relative size of the face of the stone structure parallel to image plane.

Framing refers to the image plane, which is infinitely thin (which is what a "plane" is). the framing of all the foreground (in front of the image plane) and the background (behind the image plane) cannot remain constant if location changes and framing of the main subject stays the same.

In some frames of that animation there are people on the beach near the stone structure, in others there aren't (because they are outside the field of view) , I'm not sure how that can mean that the framing remains the same.

 

[WunWegWunDarWun]

Here is an example of a two-point perspective image:

And here is a crop of it that makes for a one-point perspective image:

No, that's still two-point. I'll draw it for you if you don't see it.

If you mean the street between the church and the office building feel free to imagine it also cropped, do the internal walls of the building also make it a two-point perspective ?

The reason for the confusion is simply that "perspective" has a different meaning in geometry vs. the one in art and graphics.

When discussing perspective of photos 99% times we actually mean the later

Wrong. We never mean the one discussed in art and graphics.

I think you do, in every discussion about portrait fl, equivalency etc. - the graphic meaning isn't limited to classification by vanishing points.

 

[Tom Axford]

The reason for the confusion is simply that "perspective" has a different meaning in geometry vs. the one in art and graphics.

When discussing perspective of photos 99% times we actually mean the later

Wrong. We never mean the one discussed in art and graphics.

"We" being the royal "we", I presume!

 

[richiebee]

...did you manage to shoot that image without convergence?

I didn't, it is a random creative-commons photo demonstrating two-point perspective, but it could have been achieved by any of the standard ways - keystone correction, lens shift or just shooting from the height equal to the middle of building.

Since the perspective has been artificially manipulated, how can your post have any integrity?

A. which one of the above mentioned methods do you consider artificial and what makes it artificial relative to the others ?

keystone correction and tilt shift are both manipulated based on an interaction, based on content and desired result. Manipulation rather than artificial is the key word.

Photographing from half way up the building is not manipulation. It’s changing the composition. However, we can tell from the photograph that that wasn’t the case.

B. The post could have just as easily use a drawn sketch

Which also wouldn’t have proved anything.