Is this correct?

[William W]

Be fair Bill I did mention that later. . .

Huh?

I was not being unfair nor picking nits: I merely wanted clarity of your meaning, for archival purposes of this thread.

I still do not see where you attributed the reference of a 100mm Lens to using it on a Full Frame camera . . .

"Exactly Bill but the problem is that some crop and show this aspect, others talk about it more technically and it all seems to help cause confusion where as the basics are very simple to understand and easy to demonstrate - all people need to remember is that circa 100mm will give something akin to an eye perspective and that departures will not do that as they get further away. The effects in this context are as expected, for shortening etc. This is the useful practical aspect of the effect. Some tutorials start of by saying it's bunkum, that really does help people.

John
-"

I hope you had a nice meal.

WW

[ajohnw]

Huh?

I was not being unfair nor picking nits: I merely wanted clarity of your meaning, for archival purposes of this thread.

I still do not see where you attributed the reference of a 100mm Lens to using it on a Full Frame camera . . .



I hope you had a nice meal.

WW

Sorry Bill took it the wrong way. I mentiond 100mm equivalent on crop some where. If not I had better edit it.
Edit seems I didn't. I'll leave it as it is.

Good meal. Drank a Speckled Hen with it. Next decision at home was wine, Glenburgie, Glayva or Mount Gay rum - last one won.

John
-

[William W]

Thanks. No Problem.
(I probably would have chosen the Scotch)

[AB26]

if you sat for an exam set by any respectable institution and a question was asked about "Perspective" - I believe that you would be marked incorrect.

WW

William,

I don’t really mind failing your test. I would be more concerned about failing a comprehension test on what the author has written and what he is trying to explain to me.

Kind regards.

PS. Take note, he is not talking about lens distortion, he talks about perspective distortion.

[AB26]

Nononono....

Perspective is not defined in that way, and a lens will not distort it. Look at this image of a toy car in a parking lot. [/IMG]

Now I challenge you Urban to take the same shot, lying flat on the ground, using a 28mm lens with the toy car close to you and see the difference. The perspective will change.

[Inkanyezi]

Now I challenge you Urban to take the same shot, lying flat on the ground, using a 28mm lens with the toy car close to you and see the difference. The perspective will change.

You might know that I need not lie flat on the ground to take ground level shots. Only the camera has to be there. The toy car shot indeed was not taken with the camera as low as possible, but on a small tabletop tripod.

Of course it may be placed on the ground, but perspective will not change, as long as the vantage point is the same. However a 28 mm lens will have a narrower field of view, so the framing would be different. I could take it with a 28 mm, but to see what the 28 mm would do from the same vantage point, you need only crop the image to the 28 mm angle of view.

If however I use a 28 mm lens and take it with the same framing, I have to move away from the toy car, and distance hence will change. When the distance changes, the perspective is different, but it is not a function of the lens. With a longer distance to the first little car, perspective will become a bit compressed compared to the image I took with the 17 mm lens.

[AB26]

perspective will become a bit compressed compared to the image I took with the 17 mm lens.

Is that not perspective that is distorted?

[Inkanyezi]

perspective will become a bit compressed compared to the image I took with the 17 mm lens.

Is that not perspective that is distorted?

No, perspective will not be distorted, just different from a different vantage point.

The lens does nothing to perspective. Only the distance.

You might appreciate it by thinking of your viewing distance to the image on your screen or printed on paper. When you look at a print, you usually do it from a certain distance.

• If your viewing distance for the image gives you the same viewing angle as the angle of view of the lens, perspective will be correct.
  -
• If your viewing distance is longer, so that your angle of view is narrower than the angle of view of the camera, you might think that the perspective is exaggerated, but it is only your vantage point regarding the image that is longer than the camera's vantage point regarding the subject.
  -
• If your viewing distance is shorter, so that your angle of view is more wide than that of the camera, you might regard the perspective as compressed.

So if you look at a wide angle shot from very close to the image, perspective will look perfectly normal, and if you look at a tele shot from a longer distance, its perspective will not be compressed, but perfectly normal. In this latter case however, you will see the image very small, and bringing it closer will throw the perspective off, creating what you would see through a telescope. But the perspective in the image is only governed by the distance to the elements of the subject.

[AB26]

Urban,

Before this discussion turns into an argument.

Let’s start from the very beginning.

Nononono....

Perspective is not defined in that way,

You disagree with the definition of perspective.

That is how the English Dictionary defines perspective and in the HAT (Handwoordeboek vir die Afrikaanse Taal) (the bible of the Afrikaans Language) it is defined in the exact same way.

If there is a different definition of perspective we are not talking about the same thing here and we will stay on different pages throughout the discussion.

[Adrian]

Surely perspective is a simple concept? There are many different dictionary definitions, but they have a similar perspective..(sorry about that).

All that we are really saying is that when we see, we compare objects in relationship to each other. So if you hold your finger in front of your face it will look large, but if you hold it up at arms length it will look smaller. Your finger has not changed and nor has your eyesight, but the distance between your finger and your eye has changed.

Introducing an inanimate third object into the scene, such as a camera, can logically have no effect whatsoever on the perspective of the finger.

[Inkanyezi]

Urban,

Before this discussion turns into an argument.

Let’s start from the very beginning.

You disagree with the definition of perspective.

Definition of perspective:
"the art of representing three-dimensional 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."

That is how the English Dictionary defines perspective and in the HAT (Handwoordeboek vir die Afrikaanse Taal) (the bible of the Afrikaans Language) it is defined in the exact same way.

If there is a different definition of perspective we are not talking about the same thing here and we will stay on different pages throughout the discussion.

There are many different definitions, as you may clearly note in most dictionaries.
For example Merriam-Webster:
http://www.merriam-webster.com/dictionary/perspective
or The Free Dictionary:
http://www.thefreedictionary.com/perspective

There are also very good articles in Wikipedia regarding perspective:
http://en.wikipedia.org/wiki/Vanishing_point
http://en.wikipedia.org/wiki/Perspective_%28visual%29
http://nl.wikipedia.org/wiki/Lijnperspectief
http://nl.wikipedia.org/wiki/Project...jk_perspectief

Perspective is perceived, regardless of any two-dimensional representation.
It is there, whether you make an image or not.
When you look at a scene, you will perceive perspective.

So we could re-phrase the simplified approach you outlined here:

Definition of perspective:
"the art of representing three-dimensional 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."

Re-phrasing it, correcting the obvious flaws, it becomes:

One aspect of perspective is that it can be regarded as "an art of representing three-dimensional objects on a two-dimensional surface so as to give an impression of their height, width, depth, and position in relation to each other."

A camera lens will capture the image as it appears from its vantage point, the point where its entrance pupil is located. A rectilinearly imaging camera lens will not alter perspective in any way when it records an image on a two-dimensional surface. All straight perspective lines will be straight and those that are parallel will meet at the same vanishing point. No distortion of perspective will take place when you capture an image with a lens that does not distort straight lines.

However, when taking images with a wide angle lens, a nearby object may fill substantial part of the image area, while more distant objects fill relatively small parts of the image area. Their relative distance from the camera varies more than the same objects with the same framing, when shot with a narrow angle. In the toy car image, the distance to the toy is a couple of decimetres, while the distance to the other cars is several metres. If I could back off to use a tele lens with the same framing of those objects, the toy car would take up much less of the image area, as it would then also be several metres from the camera, and the relative distance difference would be small. In neither case will the perspective be distorted.

Using the wide angle lens at close distance can accentuate, or as some put it "exaggerate", perspective, and using the narrow angle tele lens at a large distance may subdue perspective, making it closer to isometric projection, but there is no way to avoid perspective as long as you use a photographic lens on a camera to register your image, and no rectilinearly reproducing lens will distort it.

If you would prefer sticking to a more flat-worldly take on perspective, quite clearly, we are not talking about the same thing.

[William W]

William,

I don’t really mind failing your test. I would be more concerned about failing a comprehension test on what the author has written and what he is trying to explain to me.

There was absolutely no miscomprehension by myself in the interpretation of the author’s meaning and uses of the word “perspective” in the passage that is linked in the OP. That is quite obvious upon reading (my initial) post #3, an extract here:

“What the author is doing is using the term ‘perspective’ in a NON TECHNICAL sense and he is also confusing FIELD OF VIEW and transposing that term to a relationship to FOCAL LENGTHS for different CAMERA FORMAT.”

WW

[William W]

PS. Take note, he is not talking about lens distortion, he talks about perspective distortion.

Already addressed. Here is an extract from Post#8:

Maybe he thinks that he is using the word technically correctly, but he isn't.

I think the author uses the word [perspective] twice -

“But print size aside, it's often easy to detect medium format images even when viewing on the web. It has a certain something, a signature look that is often recognizable but hard to articulate. It comes from the lack of perspective distortion. This makes photos look more natural, closer to what your eye sees in the real world.”


There is not any [Perspective Distortion].

> Of a Lens - there may be: Barrel Distortion; Pincushion Distortion . . . etc.

> Of a picture due to Camera Viewpoint there may be: Keystoning; Foreshortening, Convergence etc (the appearance of which might be exacerbated by the distortions of the lens which is used.)

Note the word ‘distortion’ is NOT usually used in conjunction with these terms like “convergence”, nor (pedantically/technically ) is the word “distortion” to be used with the word “perspective”.

The colloquial joining of the word “distortion” to “perspective is the source of a lot of confusion/misinformation: especially if the words are NOT defined at the outset.

*

“The key point as a result of that difference is that even though the field of view is wider, the geometry, or "look," of the 50mm focal length remains. You don't get the exaggerated perspective that wide angle lenses usually produce on 35mm cameras.”
One cannot “exaggerate” perspective: it simply just is.

Both the above uses of the word "perspective" are colloquial and are outside of the context of the Technical use of the word “Perspective” for Photography and allied Subjects (such as Optics, Technical Drawing etc.).

(My bold and underlined for emphasis now, of what had already been stated previoulsy in this thread)

WW

[William W]

Urban,

Within the context of "perspective" that we two are discussing, you mention several times that Perspective is only contingent on Camera Distance.

It is also contingent on Camera Elevation, relative to the Subject.

There are two elements to Camera Viewpoint (or as you mention Camera "Vantage" Point) and the second is Camera Elevation, which is often overlooked - because it doesn't often matter.

But - for one simple example: let's assume we take two Portraits of a young child who is standing close to us and we use a 35mm lens on a 135 Format Camera.

For the first shot we stand up tall and let's assume we are 6ft tall - the foreshortening (of the Subject) will be most apparent in a particular sense as the Camera Elevation is much higher than the Child.

Then we move the camera to a lower elevation, but keep the same Camera Distance to the Child - the Perspective will change.

Not just apropos using Wide Angle Lenses - A similar consideration is employed when reckoning the optimal CAMERA ELEVATION for (TV Cameras) when covering Sporting Events - I am most familiar with Cricket and there is much consideration as to how high the Camera Towers are relative to their distance from the Wicket.

WW

[Inkanyezi]

I think elevation is a function of choosing the perspective, quite clearly, as it defines the height of the horizon.

However, in the example of taking a child from above, there's another element included, as the camera will certainly be tilted downward substantially. The "horizon" when the lens does not tilt or shift, will always be in line with the optical axis of the lens - hence we will have a horizon somewhere below the ground, behind the head of the youngster when we point the camera down. Understandably, the distance to the head is short, and the distance to his feet is larger.

So elevation and tilting the camera will define the vanishing point/line that the photographer chooses for that particular image. Often we use restitution to change that afterwards. It was done in the past when enlarging, and now it is done in PP software. Such a correction has been applied in the image of the toy car in the parking lot, as vertical lines were converging to a point somewhere below the ground, because the camera was pointed down. The sofware control is called "perspective".

[William W]

Thanks for clarifying that.

The example of the Child’s Portrait was a (purposely) an extreme example. Yes there are other elements – especially of SD to the Child’s Feet and the Child’s head.

The example of the TV Towers Height was much less so extreme, but relevant.

There are other examples where subtle uses of Camera Elevation affect Perspective at the same Subject Distance.

One example, for Portraiture: some of us will still often drop to Waist Level for the Full Length Shot (and use a Normal FL) and then move to Eye Level for the Half shot and Bust Shot (using a Moderate Telephoto FL). This technique was more often used with Medium Format SLR and TLR Cameras in the past: but I still see a few others do it today, using DSLRs.

WW

[Inkanyezi]

There are other examples where subtle uses of Camera Elevation affect Perspective at the same Subject Distance.

One example, for Portraiture: some of us will still often drop to Waist Level for the Full Length Shot (and use a Normal FL) and then move to Eye Level for the Half shot and Bust Shot (using a Moderate Telephoto FL). This technique was more often used with Medium Format SLR and TLR Cameras in the past: but I still see a few others do it today, using DSLRs.

My first job, 1962, in the photo business was in the lab of a portrait studio, where I made all printing. The camera of choice there was the Tele Rolleiflex, a Rolleiflex TLR with a 135 mm lens. A studio stand of the column type on wheels was used, and the photographer climbed up on a platform on it to see the screen, as the camera was in a rather high position for a TLR, where the matte screen is on top of the camera. Images were taken at head height of the customers. No full length shots were ever taken while I worked there, they were all breast shots.

When finishing, we mostly tilted the images a bit and made a note on the negative file of how we had made it, in case the customer would want more of the same.

[William W]

ah!

I know well those big Camera Stands with wheels. I mostly inverted the TLR and looked upwards into the screen. Used a (wooden) ladder for the 5x4 work - it was all very heavy gear by today's standards.

***

Also remember tilting the neg and or base board to enhance the line/size of the Bust; reduce the nose; slim the hips etc . . . good to note the incline for each neg - I don't think we did that . . . I was working for Studio owned by a Pommy fellow - a really tough guy: he gave everyone 0 chances; that's how I got out of the studio and covered my first Wedding - the assigned Photographer was about ten minutes late to the briefing and he never worked for the Studio again.

***

With that as some of your first hand experience, you must be about my age - about 36 or 37?

WW

Addendum - just noted that you supplied a date - I did my first wedding around '74 while still at College - you might be a few years older than I, maybe you might be even nearly 40!

[PhotomanJohn]

With that as some of your first hand experience, you must be about my age - about 36 or 37

I had no idea that I am five years short of being twice your ages! You are both very knowledgeable for being so young.

John

[Inkanyezi]

you might be a few years older than I, maybe you might be even nearly 40!

Not too far off. In fact, yesterday was my 69 birthday. I still cannot fathom that so much time has passed.